[Linux-kernel-mentees] [RFC, WIP, v6 00/10] media: vidtv: implement a virtual DVB driver

[Linux-kernel-mentees] [RFC, WIP, v6 00/10] media: vidtv: implement a virtual DVB driver

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

This series is work in progress. It represents the current work done on a
virtual DVB driver for the Linux media subsystem. I am new to the media
subsystem and to kernel development in general.

This driver aims to:
	- Serve as template for new DVB driver writers
	- Help userspace application writers in general
	- Push fake audio/video to userspace for testing
		purposes
	- Push debug information to userspace via debugfs

This should currently be able to feed PSI and PCM audio data to
userspace.

I appreciate any feedback!

Changes in v6:
	Addressed the following issues:
	- Makefile was not actually compiling everything;
	- The bridge driver should be a platform driver;
	- There are lots of warnings and other errors produced
	by the driver.

Changes in v5:

Removed all calls to WARN_ON in favor of pr_warn_ratelimited
Add a #define for pr_fmt
Reworked the byte swapping logic for big/little endian support:
	big endian fields now prepended with __beXX for 'sparse' checks
	bitfields now laid in reverse order if LITTLE_ENDIAN_BITFIELD
		is set

media: vidtv: implement a tuner driver
	Return -EINVAL instead of -1 in vidtv_tuner_check_frequency_shift
media: vidtv: implement a demodulator driver
	Add POLL_THRD_TIME #define
	Implement dvb_frontend_ops as a single struct instead of three
media: vidtv: move config structs into a separate header
	Removed this commit, configs are now in vidtv_tuner.h and vidtv_demod.h
media: vidtv: add a bridge driver
	module_param: all fs permissions set to 0
	removed param 'chosen_delsys'
	module_param: removed "optional" string: all module_params are optional
	renamed vidtv_bridge -> vidtv_bridg: so the source code and module names
		are different
media: vidtv: add wrappers for memcpy and memset
	Added kernel-docs
	write address is now computed internally
media: vidtv: add MPEG TS common code
	Drop packets if the buffer is full
media: vidtv: implement a PSI generator
	Removed vidtv_psi_ts_psi_write_stuffing()
	Forcibly align misaligned buffers
	Drop packets if buffer is full
media: vidtv: implement a PES packetizer
	Remove vidtv_extract_bits() in favor of GENMASK() and bitwise &
	Forcibly align misaligned buffers
media: vidtv: Implement a SMPTE 302M encoder
	Added kernel-docs for struct vidtv_encoder
media: vidtv: Add a MPEG Transport Stream Multiplexer
	Added check for minimum and maximum buffer size.
	Drop packets if buffer is full


Changes in v4:
Added a PES packetizer
Implemented a minimum version of the SMPTE 302m encoder for AES3 audio
Fixed endianness in the PSI generator, converting fields to big endian where applicable
Added a minimal TS mux abstraction

Changes in v3:
Added a bridge driver
Renamed the driver to vidtv
Renamed/reworked commits into smaller pieces
Moved the driver into its own directory
Fixed the code for the signal strength in the tuner
Removed useless enums in the tuner driver (e.g. lock_status, power_status...)
Reworked the logic for the poll_snr thread in the demodulator driver
Moved MPEG related code to the bridge driver, as it controls the demux logic
Changed literals to #defines, used sizeof in place of integer literals when
computing the size of PSI structs
Moved the MPEG PSI tables to the heap to reduce stack space usage
Now using usleep_range in place of msleep_interruptible in the MPEG TS thread
Wrapped memcpy and memset to protect against buffer overflow when writing to the
MPEG TS buffer.

Changes in v2:
Attempted not to break assignments into multiple lines as much as possible.
Code now passes checkpatch strict mode

media: dvb_dummy_tuner: implement driver skeleton	
Changed snr values to mili db
Return value from 0-100 to indicate how far off the requested
frequency is from a valid one

Use the frequency shift to interpolate between 34dB and 10dB if
we can not match against the SNR lookup table
Remove sleep calls for suspend/resume

Fix memcpy call for the config struct

media: dvb_dummy_fe.c: lose TS lock on bad snr
Randomly recover the TS lock if the signal quality improves

media: dvb_dummy_fe.c: write PSI information into DMX buffer
Split the patch into multiple header/source files

Hexadecimal literals are now lower case

Prefer short function names / reduce function signatures

Add #defines for constants when computing section lengths

Change signature for functions that take a dummy channel as
argument (i.e. channels* is now channels[NUM_CHANNELS])

Daniel W. S. Almeida (10):
  media: vidtv: add Kconfig entry
  media: vidtv: implement a tuner driver
  media: vidtv: implement a demodulator driver
  media: vidtv: add a bridge driver
  media: vidtv: add wrappers for memcpy and memset
  media: vidtv: add MPEG TS common code
  media: vidtv: implement a PSI generator
  media: vidtv: implement a PES packetizer
  media: vidtv: Implement a SMPTE 302M encoder
  media: vidtv: Add a MPEG Transport Stream Multiplexer

 arch/Kconfig                                  |    2 +-
 drivers/media/dvb-core/dvbdev.c               |    1 +
 drivers/media/test-drivers/Kconfig            |   10 +
 drivers/media/test-drivers/Makefile           |    1 +
 drivers/media/test-drivers/vidtv/Kconfig      |   11 +
 drivers/media/test-drivers/vidtv/Makefile     |    9 +
 .../media/test-drivers/vidtv/vidtv_bridge.c   |  511 ++++++++
 .../media/test-drivers/vidtv/vidtv_bridge.h   |   41 +
 .../media/test-drivers/vidtv/vidtv_channel.c  |  339 ++++++
 .../media/test-drivers/vidtv/vidtv_channel.h  |   66 ++
 .../media/test-drivers/vidtv/vidtv_common.c   |   86 ++
 .../media/test-drivers/vidtv/vidtv_common.h   |   34 +
 .../media/test-drivers/vidtv/vidtv_demod.c    |  444 +++++++
 .../media/test-drivers/vidtv/vidtv_demod.h    |   41 +
 .../media/test-drivers/vidtv/vidtv_encoder.h  |  103 ++
 drivers/media/test-drivers/vidtv/vidtv_mux.c  |  434 +++++++
 drivers/media/test-drivers/vidtv/vidtv_mux.h  |  105 ++
 drivers/media/test-drivers/vidtv/vidtv_pes.c  |  450 +++++++
 drivers/media/test-drivers/vidtv/vidtv_pes.h  |  186 +++
 drivers/media/test-drivers/vidtv/vidtv_psi.c  | 1055 +++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_psi.h  |  420 +++++++
 .../media/test-drivers/vidtv/vidtv_s302m.c    |  636 ++++++++++
 .../media/test-drivers/vidtv/vidtv_s302m.h    |  119 ++
 drivers/media/test-drivers/vidtv/vidtv_ts.c   |  157 +++
 drivers/media/test-drivers/vidtv/vidtv_ts.h   |  120 ++
 .../media/test-drivers/vidtv/vidtv_tuner.c    |  408 +++++++
 .../media/test-drivers/vidtv/vidtv_tuner.h    |   26 +
 27 files changed, 5814 insertions(+), 1 deletion(-)
 create mode 100644 drivers/media/test-drivers/vidtv/Kconfig
 create mode 100644 drivers/media/test-drivers/vidtv/Makefile
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_encoder.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.h

-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 01/10] media: vidtv: add Kconfig entry

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Add the necessary Kconfig entries and a dummy Makefile to compile the new
virtual DVB test driver (vidtv).

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/Kconfig        | 10 ++++++++++
 drivers/media/test-drivers/Makefile       |  1 +
 drivers/media/test-drivers/vidtv/Kconfig  | 11 +++++++++++
 drivers/media/test-drivers/vidtv/Makefile |  2 ++
 4 files changed, 24 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/Kconfig
 create mode 100644 drivers/media/test-drivers/vidtv/Makefile

diff --git a/drivers/media/test-drivers/Kconfig b/drivers/media/test-drivers/Kconfig
index 188381c855939..7d273a8a7acc2 100644
--- a/drivers/media/test-drivers/Kconfig
+++ b/drivers/media/test-drivers/Kconfig
@@ -4,6 +4,10 @@ menuconfig V4L_TEST_DRIVERS
 	bool "V4L test drivers"
 	depends on VIDEO_DEV
 
+menuconfig DVB_TEST_DRIVERS
+	bool "DVB test drivers"
+	depends on DVB_CORE && MEDIA_SUPPORT && I2C
+
 if V4L_TEST_DRIVERS
 
 source "drivers/media/test-drivers/vimc/Kconfig"
@@ -24,3 +28,9 @@ config VIDEO_VIM2M
 source "drivers/media/test-drivers/vicodec/Kconfig"
 
 endif #V4L_TEST_DRIVERS
+
+if DVB_TEST_DRIVERS
+
+source "drivers/media/test-drivers/vidtv/Kconfig"
+
+endif #DVB_TEST_DRIVERS
diff --git a/drivers/media/test-drivers/Makefile b/drivers/media/test-drivers/Makefile
index 74410d3a9f2d2..9f0e4ebb2efe7 100644
--- a/drivers/media/test-drivers/Makefile
+++ b/drivers/media/test-drivers/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_VIDEO_VIMC)		+= vimc/
 obj-$(CONFIG_VIDEO_VIVID)		+= vivid/
 obj-$(CONFIG_VIDEO_VIM2M)		+= vim2m.o
 obj-$(CONFIG_VIDEO_VICODEC)		+= vicodec/
+obj-$(CONFIG_DVB_VIDTV)			+= vidtv/
diff --git a/drivers/media/test-drivers/vidtv/Kconfig b/drivers/media/test-drivers/vidtv/Kconfig
new file mode 100644
index 0000000000000..22c4fd39461f1
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/Kconfig
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config DVB_VIDTV
+	tristate "Virtual DVB Driver (vidtv)"
+	depends on DVB_CORE && MEDIA_SUPPORT && I2C
+	help
+	  The virtual DVB test driver serves as a reference DVB driver and helps
+	  validate the existing APIs in the media subsystem. It can also aid developers
+	  working on userspace applications.
+
+
+	  When in doubt, say N.
diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
new file mode 100644
index 0000000000000..d1558d84eeaed
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 02/10] media: vidtv: implement a tuner driver

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

The virtual DVB test driver serves as a reference DVB driver and helps
validate the existing APIs in the media subsystem. It can also aid developers
working on userspace applications.

This dummy tuner should support common TV standards such as DVB-T/T2/S/S2,
ISDB-T and ATSC when completed.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/Makefile     |   3 +
 .../media/test-drivers/vidtv/vidtv_tuner.c    | 408 ++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_tuner.h    |  26 ++
 3 files changed, 437 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.h

diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index d1558d84eeaed..58e022c094e5e 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -1,2 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 
+dvb-vidtv-tuner-objs := vidtv_tuner.o
+
+obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_tuner.c b/drivers/media/test-drivers/vidtv/vidtv_tuner.c
new file mode 100644
index 0000000000000..3f2b4b9a6d568
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_tuner.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * The vidtv tuner should support common TV standards such as
+ * DVB-T/T2/S/S2, ISDB-T and ATSC when completed.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <media/dvb_frontend.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_tuner.h"
+
+MODULE_DESCRIPTION("Virtual DVB Tuner");
+MODULE_AUTHOR("Daniel W. S. Almeida");
+MODULE_LICENSE("GPL");
+
+struct vidtv_tuner_cnr_to_qual_s {
+	/* attempt to use the same values as libdvbv5 */
+	u32 modulation;
+	u32 fec;
+	u32 cnr_ok, cnr_good;
+};
+
+static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_c_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QAM_256, FEC_NONE,  34000, 38000},
+	{ QAM_64,  FEC_NONE,  30000, 34000},
+};
+
+static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_s_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QPSK, FEC_1_2,  7000, 10000},
+
+	{ QPSK, FEC_2_3,  9000, 12000},
+	{ QPSK, FEC_3_4, 10000, 13000},
+	{ QPSK, FEC_5_6, 11000, 14000},
+
+	{ QPSK, FEC_7_8, 12000, 15000},
+};
+
+static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_s2_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QPSK,  FEC_1_2,   9000,  12000},
+	{ QPSK,  FEC_2_3,  11000,  14000},
+	{ QPSK,  FEC_3_4,  12000,  15000},
+	{ QPSK,  FEC_5_6,  12000,  15000},
+	{ QPSK,  FEC_8_9,  13000,  16000},
+	{ QPSK,  FEC_9_10, 13500,  16500},
+	{ PSK_8, FEC_2_3,  14500,  17500},
+	{ PSK_8, FEC_3_4,  16000,  19000},
+	{ PSK_8, FEC_5_6,  17500,  20500},
+	{ PSK_8, FEC_8_9,  19000,  22000},
+};
+
+static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_t_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db*/
+	{   QPSK, FEC_1_2,  4100,  5900},
+	{   QPSK, FEC_2_3,  6100,  9600},
+	{   QPSK, FEC_3_4,  7200, 12400},
+	{   QPSK, FEC_5_6,  8500, 15600},
+	{   QPSK, FEC_7_8,  9200, 17500},
+
+	{ QAM_16, FEC_1_2,  9800, 11800},
+	{ QAM_16, FEC_2_3, 12100, 15300},
+	{ QAM_16, FEC_3_4, 13400, 18100},
+	{ QAM_16, FEC_5_6, 14800, 21300},
+	{ QAM_16, FEC_7_8, 15700, 23600},
+
+	{ QAM_64, FEC_1_2, 14000, 16000},
+	{ QAM_64, FEC_2_3, 19900, 25400},
+	{ QAM_64, FEC_3_4, 24900, 27900},
+	{ QAM_64, FEC_5_6, 21300, 23300},
+	{ QAM_64, FEC_7_8, 22000, 24000},
+};
+
+struct vidtv_tuner_hardware_state {
+	bool asleep;
+	u32 lock_status;
+	u32 if_frequency;
+	u32 tuned_frequency;
+	u32 bandwidth;
+};
+
+struct vidtv_tuner_dev {
+	struct dvb_frontend *fe;
+	struct vidtv_tuner_hardware_state hw_state;
+	struct vidtv_tuner_config config;
+};
+
+static struct vidtv_tuner_dev*
+vidtv_tuner_get_dev(struct dvb_frontend *fe)
+{
+	struct i2c_client *client = fe->tuner_priv;
+
+	return i2c_get_clientdata(client);
+}
+
+static s32 vidtv_tuner_check_frequency_shift(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+	struct vidtv_tuner_config config  = tuner_dev->config;
+	u32    *valid_freqs               = NULL;
+	u32    array_sz                   = 0;
+	u32 i;
+	u32 shift;
+
+	switch (c->delivery_system) {
+	case SYS_DVBT:
+	case SYS_DVBT2:
+		valid_freqs = config.vidtv_valid_dvb_t_freqs;
+		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_t_freqs);
+		break;
+	case SYS_DVBS:
+	case SYS_DVBS2:
+		valid_freqs = config.vidtv_valid_dvb_s_freqs;
+		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_s_freqs);
+		break;
+	case SYS_DVBC_ANNEX_A:
+		valid_freqs = config.vidtv_valid_dvb_c_freqs;
+		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_c_freqs);
+		break;
+
+	default:
+		pr_warn("%s: unsupported delivery system: %u\n",
+			__func__,
+			c->delivery_system);
+
+		return -EINVAL;
+	}
+
+	for (i = 0; i < array_sz; i++) {
+		shift = abs(c->frequency - valid_freqs[i]);
+
+		if (!shift)
+			return 0;
+
+		/*
+		 * This will provide a value from 0 to 100 that would
+		 * indicate how far is the tuned frequency from the
+		 * right one.
+		 */
+		if (shift < config.max_frequency_shift_hz)
+			return shift * 100 / config.max_frequency_shift_hz;
+	}
+
+	return -EINVAL;
+}
+
+static int
+vidtv_tuner_get_signal_strength(struct dvb_frontend *fe, u16 *strength)
+{
+	struct dtv_frontend_properties *c          = &fe->dtv_property_cache;
+	const struct vidtv_tuner_cnr_to_qual_s *cnr2qual = NULL;
+	u32    array_size                          = 0;
+	s32 shift;
+	u32 i;
+
+	shift = vidtv_tuner_check_frequency_shift(fe);
+
+	switch (c->delivery_system) {
+	case SYS_DVBT:
+	case SYS_DVBT2:
+		cnr2qual   = vidtv_tuner_t_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_tuner_t_cnr_2_qual);
+		break;
+
+	case SYS_DVBS:
+		cnr2qual   = vidtv_tuner_s_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_tuner_s_cnr_2_qual);
+		break;
+
+	case SYS_DVBS2:
+		cnr2qual   = vidtv_tuner_s2_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_tuner_s2_cnr_2_qual);
+		break;
+
+	case SYS_DVBC_ANNEX_A:
+		cnr2qual   = vidtv_tuner_c_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_tuner_c_cnr_2_qual);
+		break;
+
+	default:
+		pr_warn_ratelimited("%s: unsupported delivery system: %u\n",
+				    __func__,
+				    c->delivery_system);
+		return -EINVAL;
+	}
+
+	for (i = 0; i <= array_size; i++) {
+		if (cnr2qual[i].modulation != c->modulation ||
+		    cnr2qual[i].fec != c->fec_inner)
+			continue;
+
+		if (!shift) {
+			*strength = cnr2qual[i].cnr_good;
+			return 0;
+		}
+		if (shift < 0) {	/* Channel not tuned */
+			*strength = 0;
+			return 0;
+		}
+		/*
+		 * Channel tuned at wrong frequency. Simulate that the
+		 * Carrier S/N ratio is not too good.
+		 */
+
+		*strength = cnr2qual[i].cnr_ok -
+			    (cnr2qual[i].cnr_good - cnr2qual[i].cnr_ok);
+		return 0;
+	}
+
+	/*
+	 * do a linear interpolation between 34dB and 10dB if we can't
+	 * match against the table
+	 */
+	*strength = 34 - 24 * shift / 100;
+	return 0;
+}
+
+static int vidtv_tuner_init(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+	struct vidtv_tuner_config config  = tuner_dev->config;
+
+	msleep_interruptible(config.mock_power_up_delay_msec);
+
+	tuner_dev->hw_state.asleep       = false;
+	tuner_dev->hw_state.if_frequency = 5000;
+
+	return 0;
+}
+
+static int vidtv_tuner_sleep(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	tuner_dev->hw_state.asleep = true;
+	return 0;
+}
+
+static int vidtv_tuner_suspend(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	tuner_dev->hw_state.asleep = true;
+	return 0;
+}
+
+static int vidtv_tuner_resume(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	tuner_dev->hw_state.asleep = false;
+	return 0;
+}
+
+static int vidtv_tuner_set_params(struct dvb_frontend *fe)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+	struct vidtv_tuner_config config  = tuner_dev->config;
+	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+	u32    min_freq               = fe->ops.tuner_ops.info.frequency_min_hz;
+	u32    max_freq               = fe->ops.tuner_ops.info.frequency_max_hz;
+	u32    min_bw                 = fe->ops.tuner_ops.info.bandwidth_min;
+	u32    max_bw                 = fe->ops.tuner_ops.info.bandwidth_max;
+
+	if (c->frequency < min_freq  || c->frequency > max_freq  ||
+	    c->bandwidth_hz < min_bw || c->bandwidth_hz > max_bw) {
+		tuner_dev->hw_state.lock_status = 0;
+		return -EINVAL;
+	}
+
+	tuner_dev->hw_state.tuned_frequency = c->frequency;
+	tuner_dev->hw_state.bandwidth       = c->bandwidth_hz;
+	tuner_dev->hw_state.lock_status     = TUNER_STATUS_LOCKED;
+
+	msleep_interruptible(config.mock_tune_delay_msec);
+	return 0;
+}
+
+static int vidtv_tuner_set_config(struct dvb_frontend *fe,
+				  void *priv_cfg)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	memcpy(&tuner_dev->config, priv_cfg, sizeof(tuner_dev->config));
+
+	return 0;
+}
+
+static int vidtv_tuner_get_frequency(struct dvb_frontend *fe,
+				     u32 *frequency)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	*frequency = tuner_dev->hw_state.tuned_frequency;
+
+	return 0;
+}
+
+static int vidtv_tuner_get_bandwidth(struct dvb_frontend *fe,
+				     u32 *bandwidth)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	*bandwidth = tuner_dev->hw_state.bandwidth;
+
+	return 0;
+}
+
+static int vidtv_tuner_get_if_frequency(struct dvb_frontend *fe,
+					u32 *frequency)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	*frequency = tuner_dev->hw_state.if_frequency;
+
+	return 0;
+}
+
+static int vidtv_tuner_get_status(struct dvb_frontend *fe, u32 *status)
+{
+	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
+
+	*status = tuner_dev->hw_state.lock_status;
+
+	return 0;
+}
+
+static const struct dvb_tuner_ops vidtv_tuner_ops = {
+	.init             = vidtv_tuner_init,
+	.sleep            = vidtv_tuner_sleep,
+	.suspend          = vidtv_tuner_suspend,
+	.resume           = vidtv_tuner_resume,
+	.set_params       = vidtv_tuner_set_params,
+	.set_config       = vidtv_tuner_set_config,
+	.get_bandwidth    = vidtv_tuner_get_bandwidth,
+	.get_frequency    = vidtv_tuner_get_frequency,
+	.get_if_frequency = vidtv_tuner_get_if_frequency,
+	.get_status       = vidtv_tuner_get_status,
+	.get_rf_strength  = vidtv_tuner_get_signal_strength
+};
+
+static const struct i2c_device_id vidtv_tuner_i2c_id_table[] = {
+	{"vidtv_tuner", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, vidtv_tuner_i2c_id_table);
+
+static int vidtv_tuner_i2c_probe(struct i2c_client *client,
+				 const struct i2c_device_id *id)
+{
+	struct vidtv_tuner_config *config = client->dev.platform_data;
+	struct dvb_frontend *fe           = config->fe;
+	struct vidtv_tuner_dev *tuner_dev = NULL;
+
+	tuner_dev = kzalloc(sizeof(*tuner_dev), GFP_KERNEL);
+	if (!tuner_dev)
+		return -ENOMEM;
+
+	tuner_dev->fe = config->fe;
+	i2c_set_clientdata(client, tuner_dev);
+
+	memcpy(&fe->ops.tuner_ops,
+	       &vidtv_tuner_ops,
+	       sizeof(struct dvb_tuner_ops));
+
+	fe->tuner_priv = client;
+
+	return 0;
+}
+
+static int vidtv_tuner_i2c_remove(struct i2c_client *client)
+{
+	struct vidtv_tuner_dev *tuner_dev = i2c_get_clientdata(client);
+	struct dvb_frontend *fe           = tuner_dev->fe;
+
+	memset(&fe->ops.tuner_ops, 0, sizeof(struct dvb_tuner_ops));
+	fe->tuner_priv = NULL;
+	kfree(tuner_dev);
+
+	return 0;
+}
+
+static struct i2c_driver vidtv_tuner_i2c_driver = {
+	.driver = {
+		.name                = "vidtv_tuner",
+		.suppress_bind_attrs = true,
+	},
+	.probe    = vidtv_tuner_i2c_probe,
+	.remove   = vidtv_tuner_i2c_remove,
+	.id_table = vidtv_tuner_i2c_id_table,
+};
+module_i2c_driver(vidtv_tuner_i2c_driver);
diff --git a/drivers/media/test-drivers/vidtv/vidtv_tuner.h b/drivers/media/test-drivers/vidtv/vidtv_tuner.h
new file mode 100644
index 0000000000000..46407739f5d44
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_tuner.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The Virtual DTV test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_TUNER_H
+#define VIDTV_TUNER_H
+
+#include <linux/types.h>
+#include <media/dvb_frontend.h>
+
+struct vidtv_tuner_config {
+	struct dvb_frontend *fe;
+	u32 mock_power_up_delay_msec;
+	u32 mock_tune_delay_msec;
+	u32 vidtv_valid_dvb_t_freqs[8];
+	u32 vidtv_valid_dvb_c_freqs[8];
+	u32 vidtv_valid_dvb_s_freqs[8];
+	u8  max_frequency_shift_hz;
+};
+
+#endif //VIDTV_TUNER_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 03/10] media: vidtv: implement a demodulator driver

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Implement a I2C demodulator driver, simulating support for DVB-T, DVB-C
and DVB-S.

This demodulator will periodically check the signal quality against a table
and drop the TS lock if it drops below a threshold value, regaining it in
the event that the signal improves.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/Makefile     |   3 +-
 .../media/test-drivers/vidtv/vidtv_demod.c    | 444 ++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_demod.h    |  41 ++
 3 files changed, 487 insertions(+), 1 deletion(-)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.h

diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index 58e022c094e5e..21e50c11c94d0 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
 dvb-vidtv-tuner-objs := vidtv_tuner.o
+dvb-vidtv-demod-objs := vidtv_demod.o
 
-obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o
+obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.c b/drivers/media/test-drivers/vidtv/vidtv_demod.c
new file mode 100644
index 0000000000000..15912e063cf5a
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_demod.c
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ * Based on the example driver written by Emard <emard@softhome.net>
+ */
+
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/ratelimit.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/workqueue.h>
+#include <media/dvb_frontend.h>
+
+#include "vidtv_demod.h"
+
+// FIXME: just added a random value here
+#define POLL_THRD_TIME 10 /* ms */
+
+static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_c_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QAM_256, FEC_NONE,  34000, 38000},
+	{ QAM_64,  FEC_NONE,  30000, 34000},
+};
+
+static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_s_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QPSK, FEC_1_2,  7000, 10000},
+	{ QPSK, FEC_2_3,  9000, 12000},
+	{ QPSK, FEC_3_4, 10000, 13000},
+	{ QPSK, FEC_5_6, 11000, 14000},
+	{ QPSK, FEC_7_8, 12000, 15000},
+};
+
+static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_s2_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db */
+	{ QPSK,  FEC_1_2,   9000,  12000},
+	{ QPSK,  FEC_2_3,  11000,  14000},
+	{ QPSK,  FEC_3_4,  12000,  15000},
+	{ QPSK,  FEC_5_6,  12000,  15000},
+	{ QPSK,  FEC_8_9,  13000,  16000},
+	{ QPSK,  FEC_9_10, 13500,  16500},
+	{ PSK_8, FEC_2_3,  14500,  17500},
+	{ PSK_8, FEC_3_4,  16000,  19000},
+	{ PSK_8, FEC_5_6,  17500,  20500},
+	{ PSK_8, FEC_8_9,  19000,  22000},
+};
+
+static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_t_cnr_2_qual[] = {
+	/* from libdvbv5 source code, in milli db*/
+	{   QPSK, FEC_1_2,  4100,  5900},
+	{   QPSK, FEC_2_3,  6100,  9600},
+	{   QPSK, FEC_3_4,  7200, 12400},
+	{   QPSK, FEC_5_6,  8500, 15600},
+	{   QPSK, FEC_7_8,  9200, 17500},
+
+	{ QAM_16, FEC_1_2,  9800, 11800},
+	{ QAM_16, FEC_2_3, 12100, 15300},
+	{ QAM_16, FEC_3_4, 13400, 18100},
+	{ QAM_16, FEC_5_6, 14800, 21300},
+	{ QAM_16, FEC_7_8, 15700, 23600},
+
+	{ QAM_64, FEC_1_2, 14000, 16000},
+	{ QAM_64, FEC_2_3, 19900, 25400},
+	{ QAM_64, FEC_3_4, 24900, 27900},
+	{ QAM_64, FEC_5_6, 21300, 23300},
+	{ QAM_64, FEC_7_8, 22000, 24000},
+};
+
+static const struct vidtv_demod_cnr_to_qual_s
+*vidtv_match_cnr_s(struct dvb_frontend *fe)
+{
+	struct dtv_frontend_properties *c;
+	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+	u32    array_size                          = 0;
+	u32 i;
+
+	c = &fe->dtv_property_cache;
+
+	switch (c->delivery_system) {
+	case SYS_DVBT:
+	case SYS_DVBT2:
+		cnr2qual   = vidtv_demod_t_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_demod_t_cnr_2_qual);
+		break;
+
+	case SYS_DVBS:
+		cnr2qual   = vidtv_demod_s_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_demod_s_cnr_2_qual);
+		break;
+
+	case SYS_DVBS2:
+		cnr2qual   = vidtv_demod_s2_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_demod_s2_cnr_2_qual);
+		break;
+
+	case SYS_DVBC_ANNEX_A:
+		cnr2qual   = vidtv_demod_c_cnr_2_qual;
+		array_size = ARRAY_SIZE(vidtv_demod_c_cnr_2_qual);
+		break;
+
+	default:
+		pr_warn_ratelimited("%s: unsupported delivery system: %u\n",
+				    __func__,
+				    c->delivery_system);
+		break;
+	}
+
+	for (i = 0; i <= array_size; i++)
+		if (cnr2qual[i].modulation == c->modulation &&
+		    cnr2qual[i].fec == c->fec_inner)
+			return &cnr2qual[i];
+
+	return NULL; /* not found */
+}
+
+static void vidtv_demod_poll_snr_handler(struct work_struct *work)
+{
+	/*
+	 * periodically check the signal quality and eventually
+	 * lose the TS lock if it dips too low
+	 */
+	struct vidtv_demod_state *state;
+	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+	struct vidtv_demod_config *config;
+	u16 snr = 0;
+
+	state  = container_of(work, struct vidtv_demod_state, poll_snr.work);
+	config = &state->config;
+
+	if (!state->frontend.ops.tuner_ops.get_rf_strength)
+		return;
+
+	state->frontend.ops.tuner_ops.get_rf_strength(&state->frontend, &snr);
+
+	cnr2qual = vidtv_match_cnr_s(&state->frontend);
+	if (!cnr2qual)
+		return;
+
+	if (snr < cnr2qual->cnr_ok) {
+		/* eventually lose the TS lock */
+		if (prandom_u32_max(100) < config->drop_tslock_prob_on_low_snr)
+			state->status = 0;
+	} else {
+		/* recover if the signal improves */
+		if (prandom_u32_max(100) <
+		    config->recover_tslock_prob_on_good_snr)
+			state->status = FE_HAS_SIGNAL  |
+					FE_HAS_CARRIER |
+					FE_HAS_VITERBI |
+					FE_HAS_SYNC    |
+					FE_HAS_LOCK;
+	}
+
+	schedule_delayed_work(&state->poll_snr,
+			      msecs_to_jiffies(POLL_THRD_TIME));
+}
+
+static int vidtv_demod_read_status(struct dvb_frontend *fe,
+				   enum fe_status *status)
+{
+	struct vidtv_demod_state *state = fe->demodulator_priv;
+
+	*status = state->status;
+
+	return 0;
+}
+
+static int vidtv_demod_read_ber(struct dvb_frontend *fe, u32 *ber)
+{
+	*ber = 0;
+	return 0;
+}
+
+static int vidtv_demod_read_signal_strength(struct dvb_frontend *fe,
+					    u16 *strength)
+{
+	*strength = 0;
+	return 0;
+}
+
+static int vidtv_demod_read_snr(struct dvb_frontend *fe, u16 *snr)
+{
+	*snr = 0;
+	return 0;
+}
+
+static int vidtv_demod_read_ucblocks(struct dvb_frontend *fe, u32 *ucblocks)
+{
+	*ucblocks = 0;
+	return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if it actually reads something from the hardware.
+ * Also, it should check for the locks, in order to avoid report wrong data
+ * to userspace.
+ */
+static int vidtv_demod_get_frontend(struct dvb_frontend *fe,
+				    struct dtv_frontend_properties *p)
+{
+	return 0;
+}
+
+static int vidtv_demod_set_frontend(struct dvb_frontend *fe)
+{
+	struct vidtv_demod_state *state            = fe->demodulator_priv;
+	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
+	u32    tuner_status                        = 0;
+
+	if (fe->ops.tuner_ops.set_params) {
+		fe->ops.tuner_ops.set_params(fe);
+
+		/* store the CNR returned by the tuner */
+		fe->ops.tuner_ops.get_rf_strength(fe, &state->tuner_cnr);
+
+		fe->ops.tuner_ops.get_status(fe, &tuner_status);
+		state->status = (state->tuner_cnr > 0) ?  FE_HAS_SIGNAL  |
+							  FE_HAS_CARRIER |
+							  FE_HAS_VITERBI |
+							  FE_HAS_SYNC    |
+							  FE_HAS_LOCK	 :
+							  0;
+		cnr2qual = vidtv_match_cnr_s(fe);
+
+		/* signal isn't good: might lose the lock eventually */
+		if (tuner_status == TUNER_STATUS_LOCKED &&
+		    state->tuner_cnr < cnr2qual->cnr_good) {
+			schedule_delayed_work(&state->poll_snr,
+					      msecs_to_jiffies(POLL_THRD_TIME));
+
+			state->poll_snr_thread_running = true;
+		}
+
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 0);
+	}
+
+	return 0;
+}
+
+static int vidtv_demod_sleep(struct dvb_frontend *fe)
+{
+	struct vidtv_demod_state *state = fe->demodulator_priv;
+
+	if (state->poll_snr_thread_running) {
+		cancel_delayed_work_sync(&state->poll_snr);
+		state->poll_snr_thread_running = false;
+		state->poll_snr_thread_restart = true;
+	}
+	return 0;
+}
+
+static int vidtv_demod_init(struct dvb_frontend *fe)
+{
+	struct vidtv_demod_state *state = fe->demodulator_priv;
+	u32    tuner_status             = 0;
+
+	if (state->cold_start)
+		INIT_DELAYED_WORK(&state->poll_snr,
+				  &vidtv_demod_poll_snr_handler);
+
+	/*
+	 * At resume, start the snr poll thread only if it was suspended with
+	 * the thread running. Extra care should be taken here, as some tuner
+	 * status change might happen at resume time (for example, due to an
+	 * ioctl syscall to set_frontend, or due to a release syscall).
+	 */
+	fe->ops.tuner_ops.get_status(fe, &tuner_status);
+
+	if (tuner_status == TUNER_STATUS_LOCKED &&
+	    state->poll_snr_thread_restart) {
+		schedule_delayed_work(&state->poll_snr,
+				      msecs_to_jiffies(POLL_THRD_TIME));
+
+		state->poll_snr_thread_restart = false;
+	}
+
+	state->cold_start = false;
+	return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if the demod has support for DVB-S or DVB-S2
+ */
+static int vidtv_demod_set_tone(struct dvb_frontend *fe,
+				enum fe_sec_tone_mode tone)
+{
+	return 0;
+}
+
+/*
+ * NOTE:
+ * This is implemented here just to be used as an example for real
+ * demod drivers.
+ *
+ * Should only be implemented if the demod has support for DVB-S or DVB-S2
+ */
+static int vidtv_demod_set_voltage(struct dvb_frontend *fe,
+				   enum fe_sec_voltage voltage)
+{
+	return 0;
+}
+
+static void vidtv_demod_release(struct dvb_frontend *fe)
+{
+	struct vidtv_demod_state *state = fe->demodulator_priv;
+
+	if (state->poll_snr_thread_running)
+		cancel_delayed_work_sync(&state->poll_snr);
+
+	kfree(state);
+}
+
+static const struct dvb_frontend_ops vidtv_demod_ops = {
+	.delsys = {
+		SYS_DVBT,
+		SYS_DVBT2,
+		SYS_DVBC_ANNEX_A,
+		SYS_DVBS,
+		SYS_DVBS2,
+	},
+
+	.info = {
+		.name                   = "Dummy demod for DVB-T/T2/C/S/S2",
+		.frequency_min_hz       = 51 * MHz,
+		.frequency_max_hz       = 2150 * MHz,
+		.frequency_stepsize_hz  = 62500,
+		.frequency_tolerance_hz = 29500 * kHz,
+		.symbol_rate_min        = 1000000,
+		.symbol_rate_max        = 45000000,
+
+		.caps = FE_CAN_FEC_1_2 |
+			FE_CAN_FEC_2_3 |
+			FE_CAN_FEC_3_4 |
+			FE_CAN_FEC_4_5 |
+			FE_CAN_FEC_5_6 |
+			FE_CAN_FEC_6_7 |
+			FE_CAN_FEC_7_8 |
+			FE_CAN_FEC_8_9 |
+			FE_CAN_FEC_AUTO |
+			FE_CAN_QAM_16 |
+			FE_CAN_QAM_64 |
+			FE_CAN_QAM_32 |
+			FE_CAN_QAM_128 |
+			FE_CAN_QAM_256 |
+			FE_CAN_QAM_AUTO |
+			FE_CAN_QPSK |
+			FE_CAN_FEC_AUTO |
+			FE_CAN_INVERSION_AUTO |
+			FE_CAN_TRANSMISSION_MODE_AUTO |
+			FE_CAN_GUARD_INTERVAL_AUTO |
+			FE_CAN_HIERARCHY_AUTO,
+	},
+
+	.release = vidtv_demod_release,
+
+	.init  = vidtv_demod_init,
+	.sleep = vidtv_demod_sleep,
+
+	.set_frontend = vidtv_demod_set_frontend,
+	.get_frontend = vidtv_demod_get_frontend,
+
+	.read_status          = vidtv_demod_read_status,
+	.read_ber             = vidtv_demod_read_ber,
+	.read_signal_strength = vidtv_demod_read_signal_strength,
+	.read_snr             = vidtv_demod_read_snr,
+	.read_ucblocks        = vidtv_demod_read_ucblocks,
+
+	/* For DVB-S/S2 */
+	.set_voltage = vidtv_demod_set_voltage,
+	.set_tone    = vidtv_demod_set_tone,
+};
+
+static const struct i2c_device_id vidtv_demod_i2c_id_table[] = {
+	{"vidtv_demod", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, vidtv_demod_i2c_id_table);
+
+static int vidtv_demod_i2c_probe(struct i2c_client *client,
+				 const struct i2c_device_id *id)
+{
+	struct vidtv_demod_state *state;
+
+	/* allocate memory for the internal state */
+	state = kzalloc(sizeof(*state), GFP_KERNEL);
+	if (!state)
+		return -ENOMEM;
+
+	/* create dvb_frontend */
+	memcpy(&state->frontend.ops,
+	       &vidtv_demod_ops,
+	       sizeof(struct dvb_frontend_ops));
+
+	state->frontend.demodulator_priv = state;
+	i2c_set_clientdata(client, state);
+
+	return 0;
+}
+
+static int vidtv_demod_i2c_remove(struct i2c_client *client)
+{
+	struct vidtv_demod_state *state = i2c_get_clientdata(client);
+
+	memset(&state->frontend.ops, 0, sizeof(struct dvb_frontend_ops));
+	state->frontend.demodulator_priv = NULL;
+	kfree(state);
+
+	return 0;
+}
+
+static struct i2c_driver vidtv_demod_i2c_driver = {
+	.driver = {
+		.name                = "vidtv_demod",
+		.suppress_bind_attrs = true,
+	},
+	.probe    = vidtv_demod_i2c_probe,
+	.remove   = vidtv_demod_i2c_remove,
+	.id_table = vidtv_demod_i2c_id_table,
+};
+
+module_i2c_driver(vidtv_demod_i2c_driver);
+
+MODULE_DESCRIPTION("Virtual DVB Demodulator Driver");
+MODULE_AUTHOR("Daniel W. S. Almeida");
+MODULE_LICENSE("GPL");
diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.h b/drivers/media/test-drivers/vidtv/vidtv_demod.h
new file mode 100644
index 0000000000000..b14957d9d4ea0
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_demod.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * The Virtual DTV test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ * Based on the example driver written by Emard <emard@softhome.net>
+ */
+
+#ifndef VIDTV_DEMOD_H
+#define VIDTV_DEMOD_H
+
+#include <linux/dvb/frontend.h>
+#include <media/dvb_frontend.h>
+
+struct vidtv_demod_cnr_to_qual_s {
+	/* attempt to use the same values as libdvbv5 */
+	u32 modulation;
+	u32 fec;
+	u32 cnr_ok, cnr_good;
+};
+
+struct vidtv_demod_config {
+	/* probability of losing the lock due to low snr */
+	u8 drop_tslock_prob_on_low_snr;
+	/* probability of recovering when the signal improves */
+	u8 recover_tslock_prob_on_good_snr;
+};
+
+struct vidtv_demod_state {
+	struct dvb_frontend frontend;
+	struct vidtv_demod_config config;
+	struct delayed_work poll_snr;
+	enum fe_status status;
+	u16 tuner_cnr;
+	bool cold_start;
+	bool poll_snr_thread_running;
+	bool poll_snr_thread_restart;
+};
+#endif // VIDTV_DEMOD_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 04/10] media: vidtv: add a bridge driver

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Digital TV devices consist of several independent hardware components which
are controlled by different drivers.
Each media device is controlled by a group of cooperating drivers with the
bridge driver as the main driver.

This patch adds a bridge driver for the Virtual Digital TV driver [vidtv].

The bridge driver binds to the other drivers, that is, vidtv_tuner and
vidtv_demod and implements the digital demux logic, providing userspace
with a MPEG Transport Stream.

Move config structs to a common header so they can be used by the bridge
driver and by their respective drivers.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>

BRIDGE WIP
---
 arch/Kconfig                                  |   2 +-
 drivers/media/dvb-core/dvbdev.c               |   1 +
 drivers/media/test-drivers/vidtv/Makefile     |   4 +-
 .../media/test-drivers/vidtv/vidtv_bridge.c   | 435 ++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_bridge.h   |  39 ++
 5 files changed, 479 insertions(+), 2 deletions(-)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.h

diff --git a/arch/Kconfig b/arch/Kconfig
index 786a85d4ad40d..ddcb4a68ee940 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -868,7 +868,7 @@ config VMAP_STACK
 	  be enabled.
 
 config ARCH_OPTIONAL_KERNEL_RWX
-	def_bool n
+	def_bool y
 
 config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
 	def_bool n
diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 80b6a71aa33e4..38c8b848c921f 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -962,6 +962,7 @@ int dvb_usercopy(struct file *file,
 }
 
 #if IS_ENABLED(CONFIG_I2C)
+#pragma clang optimize off
 struct i2c_client *dvb_module_probe(const char *module_name,
 				    const char *name,
 				    struct i2c_adapter *adap,
diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index 21e50c11c94d0..c99cd13f4adaf 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -2,5 +2,7 @@
 
 dvb-vidtv-tuner-objs := vidtv_tuner.o
 dvb-vidtv-demod-objs := vidtv_demod.o
+dvb-vidtv-bridge-objs := vidtv_bridge.o
 
-obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o
+obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o \
+			   dvb-vidtv-bridge.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
new file mode 100644
index 0000000000000..bc1c612c23013
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
@@ -0,0 +1,435 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Virtual DTV test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/moduleparam.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/time.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+
+#include "vidtv_bridge.h"
+#include "vidtv_demod.h"
+#include "vidtv_tuner.h"
+
+#define TUNER_DEFAULT_ADDR 0x68
+#define DEMOD_DEFAULT_ADDR 0x60
+
+static unsigned int drop_tslock_prob_on_low_snr;
+module_param(drop_tslock_prob_on_low_snr, uint, 0);
+MODULE_PARM_DESC(drop_tslock_prob_on_low_snr,
+		 "Probability of losing the TS lock if the signal quality is bad");
+
+static unsigned int recover_tslock_prob_on_good_snr;
+module_param(recover_tslock_prob_on_good_snr, uint, 0);
+MODULE_PARM_DESC(recover_tslock_prob_on_good_snr,
+		 "Probability recovering the TS lock when the signal improves");
+
+static unsigned int mock_power_up_delay_msec;
+module_param(mock_power_up_delay_msec, uint, 0);
+MODULE_PARM_DESC(mock_power_up_delay_msec, "Simulate a power up delay");
+
+static unsigned int mock_tune_delay_msec;
+module_param(mock_tune_delay_msec, uint, 0);
+MODULE_PARM_DESC(mock_tune_delay_msec, "Simulate a tune delay");
+
+static unsigned int vidtv_valid_dvb_t_freqs[8];
+module_param_array(vidtv_valid_dvb_t_freqs, uint, NULL, 0);
+MODULE_PARM_DESC(vidtv_valid_dvb_t_freqs,
+		 "Valid DVB-T frequencies to simulate");
+
+static unsigned int vidtv_valid_dvb_c_freqs[8];
+module_param_array(vidtv_valid_dvb_c_freqs, uint, NULL, 0);
+MODULE_PARM_DESC(vidtv_valid_dvb_c_freqs,
+		 "Valid DVB-C frequencies to simulate");
+
+static unsigned int vidtv_valid_dvb_s_freqs[8];
+module_param_array(vidtv_valid_dvb_s_freqs, uint, NULL, 0);
+MODULE_PARM_DESC(vidtv_valid_dvb_s_freqs,
+		 "Valid DVB-C frequencies to simulate");
+
+static unsigned int max_frequency_shift_hz;
+module_param(max_frequency_shift_hz, uint, 0);
+MODULE_PARM_DESC(max_frequency_shift_hz,
+		 "Maximum shift in HZ allowed when tuning in a channel");
+
+DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nums);
+
+static int vidtv_start_streaming(struct vidtv_dvb *dvb)
+{
+	if (dvb->streaming) {
+		pr_warn_ratelimited("Already streaming. Skipping.\n");
+		return 0;
+	}
+
+	dvb->streaming = true;
+	return 0;
+}
+
+static int vidtv_stop_streaming(struct vidtv_dvb *dvb)
+{
+	dvb->streaming = false;
+
+	return 0;
+}
+
+static int vidtv_start_feed(struct dvb_demux_feed *feed)
+{
+	struct dvb_demux *demux = feed->demux;
+	struct vidtv_dvb *dvb   = demux->priv;
+	int rc;
+	int ret;
+
+	if (!demux->dmx.frontend)
+		return -EINVAL;
+
+	mutex_lock(&dvb->feed_lock);
+
+	dvb->nfeeds++;
+	rc = dvb->nfeeds;
+
+	if (dvb->nfeeds == 1) {
+		ret = vidtv_start_streaming(dvb);
+		if (ret < 0)
+			rc = ret;
+	}
+
+	mutex_unlock(&dvb->feed_lock);
+	return rc;
+}
+
+static int vidtv_stop_feed(struct dvb_demux_feed *feed)
+{
+	struct dvb_demux *demux = feed->demux;
+	struct vidtv_dvb *dvb   = demux->priv;
+	int    err              = 0;
+
+	mutex_lock(&dvb->feed_lock);
+	dvb->nfeeds--;
+
+	if (!dvb->nfeeds)
+		err = vidtv_stop_streaming(dvb);
+
+	mutex_unlock(&dvb->feed_lock);
+	return err;
+}
+
+static struct dvb_frontend *vidtv_get_frontend_ptr(struct i2c_client *c)
+{
+	/* the demod will set this when its probe function runs */
+	struct vidtv_demod_state *state = i2c_get_clientdata(c);
+
+	return &state->frontend;
+}
+
+static int vidtv_master_xfer(struct i2c_adapter *i2c_adap,
+			     struct i2c_msg msgs[],
+			     int num)
+{
+	return 0;
+}
+
+static u32 vidtv_i2c_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C;
+}
+
+static const struct i2c_algorithm vidtv_i2c_algorithm = {
+	.master_xfer   = vidtv_master_xfer,
+	.functionality = vidtv_i2c_func,
+};
+
+static int vidtv_bridge_i2c_register_adap(struct vidtv_dvb *dvb)
+{
+	struct i2c_adapter *i2c_adapter = &dvb->i2c_adapter;
+
+	strscpy(i2c_adapter->name, "vidtv_i2c", sizeof(i2c_adapter->name));
+	i2c_adapter->owner      = THIS_MODULE;
+	i2c_adapter->algo       = &vidtv_i2c_algorithm;
+	i2c_adapter->algo_data  = NULL;
+	i2c_adapter->timeout    = 500;
+	i2c_adapter->retries    = 3;
+	i2c_adapter->dev.parent = &dvb->pdev->dev;
+
+	i2c_set_adapdata(i2c_adapter, dvb);
+	return i2c_add_adapter(&dvb->i2c_adapter);
+}
+
+static int vidtv_bridge_register_adap(struct vidtv_dvb *dvb)
+{
+	int ret = 0;
+
+	ret = dvb_register_adapter(&dvb->adapter,
+				   KBUILD_MODNAME,
+				   THIS_MODULE,
+				   &dvb->i2c_adapter.dev,
+				   adapter_nums);
+
+	return ret;
+}
+
+static int vidtv_bridge_dmx_init(struct vidtv_dvb *dvb)
+{
+	dvb->demux.dmx.capabilities = DMX_TS_FILTERING |
+				      DMX_SECTION_FILTERING;
+
+	dvb->demux.priv       = dvb;
+	dvb->demux.filternum  = 256;
+	dvb->demux.feednum    = 256;
+	dvb->demux.start_feed = vidtv_start_feed;
+	dvb->demux.stop_feed  = vidtv_stop_feed;
+
+	return dvb_dmx_init(&dvb->demux);
+}
+
+static int vidtv_bridge_dmxdev_init(struct vidtv_dvb *dvb)
+{
+	dvb->dmx_dev.filternum    = 256;
+	dvb->dmx_dev.demux        = &dvb->demux.dmx;
+	dvb->dmx_dev.capabilities = 0;
+
+	return dvb_dmxdev_init(&dvb->dmx_dev, &dvb->adapter);
+}
+
+static int vidtv_bridge_probe_demod(struct vidtv_dvb *dvb, u32 n)
+{
+	struct vidtv_demod_config cfg = {};
+
+	cfg.drop_tslock_prob_on_low_snr     = drop_tslock_prob_on_low_snr;
+	cfg.recover_tslock_prob_on_good_snr = recover_tslock_prob_on_good_snr;
+
+	dvb->i2c_client_demod[n] = dvb_module_probe("vidtv_demod",
+						    NULL,
+						    &dvb->i2c_adapter,
+						    DEMOD_DEFAULT_ADDR,
+						    &cfg);
+
+	/* driver will not work anyways so bail out */
+	if (!dvb->i2c_client_demod[n])
+		return -ENODEV;
+
+	/* retrieve a ptr to the frontend state */
+	dvb->fe[n] = vidtv_get_frontend_ptr(dvb->i2c_client_demod[n]);
+
+	return 0;
+}
+
+static int vidtv_bridge_probe_tuner(struct vidtv_dvb *dvb, u32 n)
+{
+	struct vidtv_tuner_config cfg = {};
+
+	cfg.fe                       = dvb->fe[n];
+	cfg.mock_power_up_delay_msec = mock_power_up_delay_msec;
+	cfg.mock_tune_delay_msec     = mock_tune_delay_msec;
+
+	memcpy(cfg.vidtv_valid_dvb_t_freqs,
+	       vidtv_valid_dvb_t_freqs,
+	       sizeof(vidtv_valid_dvb_t_freqs));
+
+	memcpy(cfg.vidtv_valid_dvb_c_freqs,
+	       vidtv_valid_dvb_c_freqs,
+	       sizeof(vidtv_valid_dvb_c_freqs));
+
+	memcpy(cfg.vidtv_valid_dvb_s_freqs,
+	       vidtv_valid_dvb_s_freqs,
+	       sizeof(vidtv_valid_dvb_s_freqs));
+
+	cfg.max_frequency_shift_hz = max_frequency_shift_hz;
+
+	dvb->i2c_client_tuner[n] = dvb_module_probe("vidtv_tuner",
+						    NULL,
+						    &dvb->i2c_adapter,
+						    TUNER_DEFAULT_ADDR,
+						    &cfg);
+
+	return (dvb->i2c_client_tuner[n]) ? 0 : -ENODEV;
+}
+
+static int vidtv_bridge_dvb_init(struct vidtv_dvb *dvb)
+{
+	int ret;
+	int i;
+	int j;
+	int k;
+	int w;
+	int l;
+
+	ret = vidtv_bridge_i2c_register_adap(dvb);
+	if (ret < 0)
+		goto fail_i2c;
+
+	ret = vidtv_bridge_register_adap(dvb);
+	if (ret < 0)
+		goto fail_adapter;
+
+	for (i = 0; i < NUM_FE; ++i) {
+		ret = vidtv_bridge_probe_demod(dvb, i);
+		if (ret < 0)
+			goto fail_demod_probe;
+
+		ret = vidtv_bridge_probe_tuner(dvb, i);
+		if (ret < 0)
+			goto fail_tuner_probe;
+
+		ret = dvb_register_frontend(&dvb->adapter, dvb->fe[i]);
+		if (ret < 0)
+			goto fail_fe;
+	}
+
+	ret = vidtv_bridge_dmx_init(dvb);
+	if (ret < 0)
+		goto fail_dmx;
+
+	ret = vidtv_bridge_dmxdev_init(dvb);
+	if (ret < 0)
+		goto fail_dmx_dev;
+
+	for (j = 0; j < NUM_FE; ++j) {
+		ret = dvb->demux.dmx.connect_frontend(&dvb->demux.dmx,
+						      &dvb->dmx_fe[j]);
+		if (ret < 0)
+			goto fail_dmx_conn;
+
+		/*
+		 * The source of the demux is a frontend connected
+		 * to the demux.
+		 */
+		dvb->dmx_fe[j].source = DMX_FRONTEND_0;
+	}
+
+	return ret;
+
+fail_dmx_conn:
+	for (j = j - 1; j >= 0; --j)
+		dvb->demux.dmx.remove_frontend(&dvb->demux.dmx,
+					       &dvb->dmx_fe[j]);
+fail_dmx_dev:
+	dvb_dmxdev_release(&dvb->dmx_dev);
+fail_dmx:
+	dvb_dmx_release(&dvb->demux);
+fail_fe:
+	for (k = i; k >= 0; --k)
+		dvb_unregister_frontend(dvb->fe[k]);
+fail_tuner_probe:
+	for (w = i; w >= 0; --w)
+		dvb_module_release(dvb->i2c_client_tuner[w]);
+
+fail_demod_probe:
+	for (l = i; l >= 0; --l)
+		dvb_module_release(dvb->i2c_client_demod[l]);
+
+fail_adapter:
+	dvb_unregister_adapter(&dvb->adapter);
+
+fail_i2c:
+	i2c_del_adapter(&dvb->i2c_adapter);
+
+	return ret;
+}
+
+static int vidtv_bridge_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct vidtv_dvb *dvb;
+
+	dvb = kzalloc(sizeof(*dvb), GFP_KERNEL);
+	if (!dvb)
+		return -ENOMEM;
+
+	dvb->pdev = pdev;
+
+	ret = vidtv_bridge_dvb_init(dvb);
+	if (ret < 0)
+		goto err_dvb;
+
+	mutex_init(&dvb->feed_lock);
+
+	platform_set_drvdata(pdev, dvb);
+
+	return ret;
+
+err_dvb:
+	kfree(dvb);
+	return ret;
+}
+
+static int vidtv_bridge_remove(struct platform_device *pdev)
+{
+	struct vidtv_dvb *dvb;
+	u32 i;
+
+	dvb = platform_get_drvdata(pdev);
+
+	mutex_destroy(&dvb->feed_lock);
+
+	for (i = 0; i < NUM_FE; ++i)
+		dvb->demux.dmx.remove_frontend(&dvb->demux.dmx,
+					       &dvb->dmx_fe[i]);
+
+	dvb_dmxdev_release(&dvb->dmx_dev);
+	dvb_dmx_release(&dvb->demux);
+
+	for (i = 0; i < NUM_FE; ++i) {
+		dvb_unregister_frontend(dvb->fe[i]);
+		dvb_frontend_detach(dvb->fe[i]);
+	}
+
+	dvb_unregister_adapter(&dvb->adapter);
+
+	return 0;
+}
+
+static void vidtv_bridge_dev_release(struct device *dev)
+{
+}
+
+static struct platform_device vidtv_bridge_dev = {
+	.name		= "vidtv_bridge",
+	.dev.release	= vidtv_bridge_dev_release,
+};
+
+static struct platform_driver vidtv_bridge_driver = {
+	.driver = {
+		.name                = "vidtv_bridge",
+		.suppress_bind_attrs = true,
+	},
+	.probe    = vidtv_bridge_probe,
+	.remove   = vidtv_bridge_remove,
+};
+
+static void __exit vidtv_bridge_exit(void)
+{
+	platform_driver_unregister(&vidtv_bridge_driver);
+	platform_device_unregister(&vidtv_bridge_dev);
+}
+
+static int __init vidtv_bridge_init(void)
+{
+	int ret;
+
+	ret = platform_device_register(&vidtv_bridge_dev);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&vidtv_bridge_driver);
+	if (ret)
+		platform_device_unregister(&vidtv_bridge_dev);
+
+	return ret;
+}
+
+module_init(vidtv_bridge_init);
+module_exit(vidtv_bridge_exit);
+
+MODULE_DESCRIPTION("Virtual Digital TV Test Driver");
+MODULE_AUTHOR("Daniel W. S. Almeida");
+MODULE_LICENSE("GPL");
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.h b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
new file mode 100644
index 0000000000000..4931bfb73273c
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The Virtual DTV test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_BRIDGE_H
+#define VIDTV_BRIDGE_H
+
+#define NUM_FE 1
+
+#include <linux/i2c.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <media/dmxdev.h>
+#include <media/dvb_demux.h>
+#include <media/dvb_frontend.h>
+
+struct vidtv_dvb {
+	struct platform_device *pdev;
+	struct dvb_frontend *fe[NUM_FE];
+	struct dvb_adapter adapter;
+	struct dvb_demux demux;
+	struct dmxdev dmx_dev;
+	struct dmx_frontend dmx_fe[NUM_FE];
+	struct i2c_adapter i2c_adapter;
+	struct i2c_client *i2c_client_demod[NUM_FE];
+	struct i2c_client *i2c_client_tuner[NUM_FE];
+
+	u32 nfeeds;
+	struct mutex feed_lock; /* start/stop feed */
+
+	bool streaming;
+};
+
+#endif // VIDTV_BRIDG_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 05/10] media: vidtv: add wrappers for memcpy and memset

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

A lot of code in this driver is for serializing structures. This is
error prone.

Therefore, prevent buffer overflows by wrapping memcpy and memset,
comparing the requested length against the buffer size.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 .../media/test-drivers/vidtv/vidtv_common.c   | 86 +++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_common.h   | 27 ++++++
 2 files changed, 113 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.c b/drivers/media/test-drivers/vidtv/vidtv_common.c
new file mode 100644
index 0000000000000..6810212087c17
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+#include "vidtv_common.h"
+
+/**
+ * vidtv_memcpy() - wrapper routine to be used by MPEG-TS
+ *	generator, in order to avoid going past the
+ *	output buffer.
+ * @to:	Starting element to where a MPEG-TS packet will
+ *	be copied.
+ * @to_offset:	Starting position of the @to buffer to be filled.
+ * @to_size:	Size of the @to buffer.
+ * @from:	Starting element of the buffer to be copied.
+ * @len:	Number of elements to be copy from @from buffer
+ *	into @to+ @to_offset buffer.
+ *
+ * Note:
+ *	Real digital TV demod drivers should not have memcpy
+ *	wrappers. We use it here because emulating MPEG-TS
+ *	generation at kernelspace requires some extra care.
+ *
+ * Return:
+ *	Returns the number of bytes written
+ */
+u32 vidtv_memcpy(void *to,
+		 size_t to_offset,
+		 size_t to_size,
+		 const void *from,
+		 size_t len)
+{
+	if (unlikely(to_offset + len > to_size)) {
+		pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size\n");
+		return 0;
+	}
+
+	memcpy(to + to_offset, from, len);
+	return len;
+}
+
+/**
+ * vidtv_memset() - wrapper routine to be used by MPEG-TS
+ *	generator, in order to avoid going past the
+ *	output buffer.
+ * @to:	Starting element to set
+ * @to_offset:	Starting position of the @to buffer to be filled.
+ * @to_size:	Size of the @to buffer.
+ * @from:	Starting element of the buffer to be copied.
+ * @ten:	Number of elements to be copy from @from buffer
+ *	into @to+ @to_offset buffer.
+ *
+ * Note:
+ *	Real digital TV demod drivers should not have memset
+ *	wrappers. We use it here because emulating MPEG-TS
+ *	generation at kernelspace requires some extra care.
+ *
+ * Return:
+ *	Returns the number of bytes written
+ */
+u32 vidtv_memset(void *to,
+		 size_t to_offset,
+		 size_t to_size,
+		 const int c,
+		 size_t len)
+{
+	if (unlikely(to_offset + len > to_size)) {
+		pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size\n");
+		return 0;
+	}
+
+	memset(to + to_offset, c, len);
+	return len;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
new file mode 100644
index 0000000000000..a3cb303cc7423
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_COMMON_H
+#define VIDTV_COMMON_H
+
+#include <linux/types.h>
+
+u32 vidtv_memcpy(void *to,
+		 size_t to_offset,
+		 size_t to_size,
+		 const void *from,
+		 size_t len);
+
+u32 vidtv_memset(void *to,
+		 size_t to_offset,
+		 size_t to_size,
+		 int c,
+		 size_t len);
+
+#endif // VIDTV_COMMON_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 06/10] media: vidtv: add MPEG TS common code

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Add code to work with MPEG TS packets, such as TS headers, adaptation
fields, PCR packets and NULL packets.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/vidtv_ts.c | 157 ++++++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_ts.h | 120 +++++++++++++++
 2 files changed, 277 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_ts.c b/drivers/media/test-drivers/vidtv/vidtv_ts.c
new file mode 100644
index 0000000000000..77908c4e85eef
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_ts.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+#include "vidtv_ts.h"
+#include "vidtv_common.h"
+
+static u32 vidtv_ts_write_pcr_bits(u8 *to, u32 to_offset, u64 pcr)
+{
+	/* Exact same from ffmpeg. PCR is a counter driven by a 27Mhz clock */
+	u64 pcr_low = pcr % 300;
+	u64 pcr_high = pcr / 300;
+	u8 *buf = to + to_offset;
+
+	*buf++ = pcr_high >> 25;
+	*buf++ = pcr_high >> 17;
+	*buf++ = pcr_high >>  9;
+	*buf++ = pcr_high >>  1;
+	*buf++ = pcr_high <<  7 | pcr_low >> 8 | 0x7e;
+	*buf++ = pcr_low;
+
+	return 6;
+}
+
+void vidtv_ts_inc_cc(u8 *continuity_counter)
+{
+	++*continuity_counter;
+	if (*continuity_counter > TS_CC_MAX_VAL)
+		*continuity_counter = 0;
+}
+
+u32 vidtv_ts_null_write_into(struct null_packet_write_args args)
+{
+	u32    nbytes                  = 0;
+	struct vidtv_mpeg_ts ts_header = {0};
+
+	ts_header.sync_byte          = TS_SYNC_BYTE;
+	ts_header.pid                = TS_NULL_PACKET_PID;
+	ts_header.payload            = 1;
+	ts_header.continuity_counter = *args.continuity_counter;
+
+	cpu_to_be16s(&ts_header.bitfield);
+
+	/* copy TS header */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.buf_sz,
+			       &ts_header,
+			       sizeof(ts_header));
+
+	be16_to_cpus(&ts_header.bitfield);
+
+	/*
+	 * Note:
+	 *	This will cause a discontinuity if the buffer is full,
+	 *	effectively dropping the packet, since nothing will get written
+	 *	but the continuity counter will still be incremented. This way,
+	 *	userspace can detect packet losses.
+	 */
+	vidtv_ts_inc_cc(args.continuity_counter);
+
+	/* fill the rest with empty data */
+	nbytes += vidtv_memset(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.buf_sz,
+			       TS_FILL_BYTE,
+			       TS_PACKET_LEN - nbytes);
+
+	/* we should have written exactly _one_ 188byte packet */
+	if (nbytes != TS_PACKET_LEN)
+		pr_warn_ratelimited("Expected exactly %d bytes, got %d\n",
+				    TS_PACKET_LEN,
+				    nbytes);
+
+	return nbytes;
+}
+
+u32 vidtv_ts_pcr_write_into(struct pcr_write_args args)
+{
+	u32    nbytes                         = 0;
+	struct vidtv_mpeg_ts ts_header        = {0};
+	struct vidtv_mpeg_ts_adaption ts_adap = {0};
+
+	ts_header.sync_byte     = TS_SYNC_BYTE;
+	ts_header.tei           = 0;
+	ts_header.payload_start = 0;
+	ts_header.pid           = args.pid;
+	ts_header.priority      = 0;
+	ts_header.scrambling    = 0;
+	/* cc is not incremented, but we need it. see 13818-1 clause 2.4.3.3 */
+	ts_header.continuity_counter = *args.continuity_counter;
+	ts_header.payload            = 0;
+	ts_header.adaptation_field   = 1;
+
+	/* 13818-1 clause 2.4.3.5 */
+	ts_adap.length = 183;
+	ts_adap.PCR    = 1;
+
+	/*
+	 * Note:
+	 *	Nothing will get written if the buffer is full, this will
+	 *	essentially drop the packet. The continuity counter is not
+	 *	updated for PCR packets, so it will be as if no PCR packet was
+	 *	sent at all.
+	 */
+
+	cpu_to_be16s(&ts_header.bitfield);
+
+	/* copy TS header */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.buf_sz,
+			       &ts_header,
+			       sizeof(ts_header));
+
+	be16_to_cpus(&ts_header.bitfield);
+
+	/* write the adap after the TS header */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.buf_sz,
+			       &ts_adap,
+			       sizeof(ts_adap));
+
+	/* write the PCR optional */
+	cpu_to_be64s(&args.pcr);
+	nbytes += vidtv_ts_write_pcr_bits(args.dest_buf,
+					  args.dest_offset + nbytes,
+					  args.pcr);
+	be64_to_cpus(&args.pcr);
+
+	nbytes += vidtv_memset(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.buf_sz,
+			       TS_FILL_BYTE,
+			       TS_PACKET_LEN - nbytes);
+
+	/* we should have written exactly _one_ 188byte packet */
+	if (nbytes != TS_PACKET_LEN)
+		pr_warn_ratelimited("Expected exactly %d bytes, got %d\n",
+				    TS_PACKET_LEN,
+				    nbytes);
+
+	return nbytes;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_ts.h b/drivers/media/test-drivers/vidtv/vidtv_ts.h
new file mode 100644
index 0000000000000..b6c638d13d14f
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_ts.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * The Virtual DVB test driver serves as a reference DVB driver and helps
+ * validate the existing APIs in the media subsystem. It can also aid
+ * developers working on userspace applications.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_TS_H
+#define VIDTV_TS_H
+
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+#define TS_SYNC_BYTE 0x47
+#define TS_PACKET_LEN 188
+#define TS_PAYLOAD_LEN 184
+#define TS_NULL_PACKET_PID 0x1fff
+#define TS_CC_MAX_VAL 0x0f /* 4 bits */
+#define TS_LAST_VALID_PID 8191
+#define TS_FILL_BYTE 0xff /* the byte used in packet stuffing */
+
+struct vidtv_mpeg_ts_adaption {
+	u8 length;
+	struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+		u8 extension:1;
+		u8 private_data:1;
+		u8 splicing_point:1;
+		u8 OPCR:1;
+		u8 PCR:1;
+		u8 priority:1;
+		u8 random_access:1;
+		u8 discontinued:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+		u8 discontinued:1;
+		u8 random_access:1;
+		u8 priority:1;
+		u8 PCR:1;
+		u8 OPCR:1;
+		u8 splicing_point:1;
+		u8 private_data:1;
+		u8 extension:1;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+	} __packed;
+	u8 data[];
+} __packed;
+
+struct vidtv_mpeg_ts {
+	u8 sync_byte;
+	union {
+		u16 bitfield;
+		struct {
+			u16 pid:13;
+			u16 priority:1;
+			u16 payload_start:1;
+			u16 tei:1;
+		} __packed;
+	} __packed;
+	struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+		u8 continuity_counter:4;
+		u8 payload:1;
+		u8 adaptation_field:1;
+		u8 scrambling:2;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+		u8 scrambling:2;
+		u8 adaptation_field:1;
+		u8 payload:1;
+		u8 continuity_counter:4;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+	} __packed;
+	struct vidtv_mpeg_ts_adaption adaption[];
+} __packed;
+
+/**
+ * struct pcr_write_args - Arguments for the pcr_write_into function.
+ * @dest_buf: The buffer to write into.
+ * @dest_offset: The byte offset into the buffer.
+ * @pid: The TS PID for the PCR packets.
+ * @buf_sz: The size of the buffer in bytes.
+ * @countinuity_counter: The TS continuity_counter.
+ * @pcr: A sample from the system clock.
+ */
+struct pcr_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	u16 pid;
+	u32 buf_sz;
+	u8 *continuity_counter;
+	u64 pcr;
+};
+
+/**
+ * struct null_packet_write_args - Arguments for the null_write_into function
+ * @dest_buf: The buffer to write into.
+ * @dest_offset: The byte offset into the buffer.
+ * @buf_sz: The size of the buffer in bytes.
+ * @countinuity_counter: The TS continuity_counter.
+ */
+struct null_packet_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	u32 buf_sz;
+	u8 *continuity_counter;
+};
+
+/* Increment the continuity counter */
+void vidtv_ts_inc_cc(u8 *continuity_counter);
+
+u32 vidtv_ts_null_write_into(struct null_packet_write_args args);
+
+u32 vidtv_ts_pcr_write_into(struct pcr_write_args args);
+
+#endif //VIDTV_TS_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 07/10] media: vidtv: implement a PSI generator

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

PSI packets contain general information about a MPEG Transport Stream.
A PSI generator is needed so userspace apps can retrieve information
about the Transport Stream and eventually tune into a (dummy) channel.

Because the generator is implemented in a separate file, it can be
reused elsewhere in the media subsystem.

Currently this commit adds support for working with 3 PSI tables:
PAT, PMT and SDT.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/vidtv_psi.c | 1037 ++++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_psi.h |  415 +++++++
 2 files changed, 1452 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_psi.c b/drivers/media/test-drivers/vidtv/vidtv_psi.c
new file mode 100644
index 0000000000000..51e9114173362
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_psi.c
@@ -0,0 +1,1037 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This file contains the logic to work with MPEG Program-Specific Information.
+ * These are defined both in ISO/IEC 13818-1 (systems) and ETSI EN 300 468.
+ * PSI is carried in the form of table structures, and although each table might
+ * technically be broken into one or more sections, we do not do this here,
+ * hence 'table' and 'section' are interchangeable for us.
+ *
+ * This code currently supports three tables: PAT, PMT and SDT. These are the
+ * bare minimum to get userspace to recognize our MPEG transport stream. It can
+ * be extended to support more PSI tables in the future.
+ *
+ * A note on endianness: MPEG layout is big-endian, therefore:
+ * - All fields spanning more than a byte must undergo 'cpu_to_beXX()'
+ * - All bitfields must have their ordering reversed if
+ *  __LITTLE_ENDIAN_BITFIELD is defined.
+ *
+ * Written by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/crc32.h>
+#include <linux/string.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_psi.h"
+#include "vidtv_common.h"
+#include "vidtv_ts.h"
+
+#define CRC_SIZE_IN_BYTES 4
+
+static u32
+vidtv_psi_ts_psi_write_into(struct psi_write_args args)
+{
+	/*
+	 * Packetize PSI sections into TS packets:
+	 * push a TS header (4bytes) every 184 bytes
+	 * manage the continuity_counter
+	 * add stuffing after the CRC
+	 */
+
+	u32  nbytes_past_boundary = (args.dest_offset % TS_PACKET_LEN);
+	bool aligned              = nbytes_past_boundary == 0;
+
+	/*
+	 * whether we need to fragment the data into multiple ts packets
+	 * if we are aligned we need to spare one byte for the pointer_field
+	 */
+	bool split = (aligned) ?
+		     args.len > TS_PAYLOAD_LEN - 1 :
+		     nbytes_past_boundary + args.len > TS_PACKET_LEN;
+
+	/* how much we can write in this packet */
+	u32 payload_write_len = (split) ?
+				(aligned)     ? TS_PAYLOAD_LEN       :
+				TS_PACKET_LEN - nbytes_past_boundary :
+				args.len;
+
+	struct psi_write_args new_args = {};
+	struct vidtv_mpeg_ts ts_header = {};
+
+	u32 nbytes = 0;  /* number of bytes written by this function */
+	u32 temp   = 0;
+
+	/* Just a sanity check, should not really happen because we stuff
+	 * the packet when we finish a section, i.e. when we write the crc at
+	 * the end. But if this happens then we have messed up the logic
+	 * somewhere.
+	 */
+	if (args.new_psi_section && !aligned) {
+		pr_warn_ratelimited("Cannot write a new PSI section in a misaligned buffer\n");
+
+		/* forcibly align and hope for the best */
+		nbytes += vidtv_memset(args.dest_buf,
+				       args.dest_offset + nbytes,
+				       args.dest_buf_sz,
+				       TS_FILL_BYTE,
+				       TS_PACKET_LEN - nbytes_past_boundary);
+
+		aligned = true;
+	}
+
+	if (aligned) {
+		/* if at a packet boundary, write a new TS header */
+		ts_header.sync_byte          = TS_SYNC_BYTE;
+		ts_header.tei                = 0;
+		ts_header.payload_start      = 1;
+		ts_header.pid                = args.pid;
+		ts_header.priority           = 0;
+		ts_header.scrambling         = 0;
+		ts_header.continuity_counter = *args.continuity_counter;
+		ts_header.payload            = 1;
+		/* no adaptation field */
+		ts_header.adaptation_field = 0;
+
+		/* copy the header */
+		nbytes += vidtv_memcpy(args.dest_buf,
+				       args.dest_offset + nbytes,
+				       args.dest_buf_sz,
+				       &ts_header,
+				       sizeof(ts_header));
+
+		/*
+		 * increment the countinuity counter since we have started a new
+		 * packet
+		 *
+		 * This will trigger a discontinuity if the buffer is full,
+		 * which is what we want: the continuity counter will be
+		 * incremented but nothing will get copied by
+		 * vidtv_memcpy/vidtv_memset, effectively dropping the packet.
+		 */
+		vidtv_ts_inc_cc(args.continuity_counter);
+	}
+
+	if (args.new_psi_section) {
+		/* write the pointer_field in the first byte of the payload */
+		temp = vidtv_memset(args.dest_buf,
+				    args.dest_offset + nbytes,
+				    args.dest_buf_sz,
+				    0x0,
+				    1);
+		/* one byte was used by the pointer field*/
+		nbytes += temp;
+		if (payload_write_len == TS_PAYLOAD_LEN)
+			payload_write_len -= temp;
+	}
+
+	/* write as much of the payload as we possibly can */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.dest_buf_sz,
+			       args.from,
+			       payload_write_len);
+
+	if (split) {
+		/* 'payload_write_len' written from a total of 'len' requested*/
+		args.len -= payload_write_len;
+		/*
+		 * recursively write the rest of the data until we do not
+		 * need to split it anymore
+		 */
+		memcpy(&new_args, &args, sizeof(struct psi_write_args));
+		new_args.from            = args.from + payload_write_len;
+		new_args.dest_offset     = args.dest_offset + nbytes;
+		new_args.new_psi_section = false;
+
+		nbytes += vidtv_psi_ts_psi_write_into(new_args);
+	}
+
+	/*
+	 * as the CRC is last in the section, stuff the rest of the
+	 * packet if there is any remaining space in there
+	 */
+	if (args.is_crc)
+		nbytes += vidtv_memset(args.dest_buf,
+				       args.dest_offset + nbytes,
+				       args.dest_buf_sz,
+				       TS_FILL_BYTE,
+				       TS_PACKET_LEN - payload_write_len);
+
+	return nbytes;
+}
+
+static u32 table_section_crc32_write_into(struct crc32_write_args args)
+{
+	/* the CRC is the last entry in the section */
+	u32 nbytes = 0;
+	__be32 crc;
+	struct psi_write_args psi_args = {};
+
+	crc = cpu_to_be32(crc32_be(0, args.dest_buf, args.dest_offset));
+
+	psi_args.dest_buf           = args.dest_buf;
+	psi_args.from               = &crc;
+	psi_args.len                = CRC_SIZE_IN_BYTES;
+	psi_args.dest_offset        = args.dest_offset;
+	psi_args.pid                = args.pid;
+	psi_args.new_psi_section    = false;
+	psi_args.continuity_counter = args.continuity_counter;
+	psi_args.is_crc             = true;
+	psi_args.dest_buf_sz        = args.dest_buf_sz;
+
+	nbytes += vidtv_psi_ts_psi_write_into(psi_args);
+
+	return nbytes;
+}
+
+struct vidtv_psi_desc *vidtv_psi_desc_init(struct vidtv_psi_desc *head,
+					   u8 type,
+					   u8 length)
+{
+	struct vidtv_psi_desc *desc;
+
+	/* alloc enough memory for the flexible array too */
+	desc = kzalloc(sizeof(*desc) + length, GFP_KERNEL);
+
+	desc->type   = type;
+	desc->length = length;
+
+	if (head) {
+		while (head->next)
+			head = head->next;
+
+		head->next = desc;
+	}
+
+	return desc;
+}
+
+void vidtv_psi_desc_destroy(struct vidtv_psi_desc *desc)
+{
+	struct vidtv_psi_desc *curr = desc;
+	struct vidtv_psi_desc *tmp  = NULL;
+
+	while (curr) {
+		tmp  = curr;
+		curr = curr->next;
+		kfree(tmp);
+	}
+}
+
+static u32
+vidtv_psi_desc_comp_len(struct vidtv_psi_desc *desc)
+{
+	u32 length = 0;
+
+	if (!desc)
+		return 0;
+
+	while (desc) {
+		length += desc->length;
+		desc    = desc->next;
+	}
+
+	return length;
+}
+
+void vidtv_psi_desc_assign(struct vidtv_psi_desc **to,
+			   struct vidtv_psi_desc *desc)
+{
+	/*
+	 * Caller must recompute the section length afterwards at some point
+	 * This function transfers ownedship of desc.
+	 * Start by cleaning the old data
+	 */
+	if (*to)
+		vidtv_psi_desc_destroy(*to);
+
+	*to = desc;  /* reassign pointer */
+}
+
+static u32 vidtv_psi_desc_write_into(struct desc_write_args args)
+{
+	/* the number of bytes written by this function */
+	u32    nbytes                  = 0;
+	struct psi_write_args psi_args = {};
+
+	psi_args.dest_buf = args.dest_buf;
+	psi_args.from     = args.desc;
+
+	psi_args.len      = sizeof_field(struct vidtv_psi_desc, type) +
+			    sizeof_field(struct vidtv_psi_desc, length);
+
+	psi_args.dest_offset        = args.dest_offset;
+	psi_args.pid                = args.pid;
+	psi_args.new_psi_section    = false;
+	psi_args.continuity_counter = args.continuity_counter;
+	psi_args.is_crc             = false;
+	psi_args.dest_buf_sz        = args.dest_buf_sz;
+
+	nbytes += vidtv_psi_ts_psi_write_into(psi_args);
+
+	/* move 'from' pointer to point to u8 data[] */
+	psi_args.from = args.desc +
+			sizeof_field(struct vidtv_psi_desc, type) +
+			sizeof_field(struct vidtv_psi_desc, length) +
+			sizeof(struct vidtv_psi_desc *);
+
+	psi_args.len         = args.desc->length;
+	psi_args.dest_offset = args.dest_offset + nbytes;
+
+	nbytes += vidtv_psi_ts_psi_write_into(psi_args);
+
+	return nbytes;
+}
+
+static u32
+vidtv_psi_table_header_write_into(struct header_write_args args)
+{
+	/* the number of bytes written by this function */
+	u32    nbytes                  = 0;
+	struct psi_write_args psi_args = {};
+
+	psi_args.dest_buf           = args.dest_buf;
+	psi_args.from               = args.h;
+	psi_args.len                = sizeof(struct vidtv_psi_table_header);
+	psi_args.dest_offset        = args.dest_offset;
+	psi_args.pid                = args.pid;
+	psi_args.new_psi_section    = true;
+	psi_args.continuity_counter = args.continuity_counter;
+	psi_args.is_crc             = false;
+	psi_args.dest_buf_sz        = args.dest_buf_sz;
+
+	nbytes += vidtv_psi_ts_psi_write_into(psi_args);
+
+	return nbytes;
+}
+
+void
+vidtv_psi_pat_table_comp_sec_len(struct vidtv_psi_table_pat *pat)
+{
+	/* see ISO/IEC 13818-1 : 2000 p.43 */
+	u16 length = 0;
+	u32 i;
+
+	/* from immediately after 'section_length' until 'last_section_number'*/
+	length += PAT_LEN_UNTIL_LAST_SECTION_NUMBER;
+
+	/* do not count the pointer */
+	for (i = 0; i < pat->programs; ++i)
+		length += sizeof(struct vidtv_psi_table_pat_program) -
+			  sizeof(struct vidtv_psi_table_pat_program *);
+
+	length += CRC_SIZE_IN_BYTES;
+
+	if (length > MAX_SECTION_LEN)
+		pr_warn_ratelimited("len %d > %d\n", length, MAX_SECTION_LEN);
+
+	pat->header.section_length = length;
+}
+
+void vidtv_psi_pmt_table_comp_sec_len(struct vidtv_psi_table_pmt *pmt)
+{
+	/* see ISO/IEC 13818-1 : 2000 p.46 */
+	u16    length                        = 0;
+	struct vidtv_psi_table_pmt_stream *s = pmt->stream;
+
+	/* from immediately after 'section_length' until 'program_info_length'*/
+	length += PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH;
+
+	pmt->desc_length  = vidtv_psi_desc_comp_len(pmt->descriptor);
+	length           += pmt->desc_length;
+
+	while (s) {
+		/* skip both pointers at the end */
+		length += sizeof(struct vidtv_psi_table_pmt_stream) -
+			  sizeof(struct vidtv_psi_desc *) -
+			  sizeof(struct vidtv_psi_table_pmt_stream *);
+
+		s->desc_length  = vidtv_psi_desc_comp_len(s->descriptor);
+		length         += s->desc_length;
+
+		s = s->next;
+	}
+
+	length += CRC_SIZE_IN_BYTES;
+
+	if (length > MAX_SECTION_LEN)
+		pr_warn_ratelimited("len %d > %d\n", length, MAX_SECTION_LEN);
+
+	pmt->header.section_length = length;
+}
+
+void vidtv_psi_sdt_table_comp_sec_len(struct vidtv_psi_table_sdt *sdt)
+{
+	/* see ETSI EN 300 468 V 1.10.1 p.24 */
+	u16    length                         = 0;
+	struct vidtv_psi_table_sdt_service *s = sdt->service;
+
+	/*
+	 * from immediately after 'section_length' until
+	 * 'reserved_for_future_use'
+	 */
+	length += SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE;
+
+	while (s) {
+		/* skip both pointers at the end */
+		length += sizeof(struct vidtv_psi_table_sdt_service) -
+			  sizeof(struct vidtv_psi_desc *) -
+			  sizeof(struct vidtv_psi_table_sdt_service *);
+
+		s->desc_length  = vidtv_psi_desc_comp_len(s->descriptor);
+		length         += s->desc_length;
+
+		s = s->next;
+	}
+
+	length += CRC_SIZE_IN_BYTES;
+
+	if (length > MAX_SECTION_LEN)
+		pr_warn_ratelimited("len %d > %d\n", length, MAX_SECTION_LEN);
+
+	sdt->header.section_length = length;
+}
+
+struct vidtv_psi_table_pat_program*
+vidtv_psi_pat_program_init(struct vidtv_psi_table_pat_program *head,
+			   u16 service_id,
+			   u16 pid)
+{
+	/*
+	 * if 'head' is attached to a table, caller should recompute
+	 * the section length afterwards at some point
+	 */
+	struct vidtv_psi_table_pat_program *program;
+
+	program = kzalloc(sizeof(*program), GFP_KERNEL);
+
+	program->service_id = cpu_to_be16(service_id);
+	/* pid for the PMT section in the TS */
+	program->pid        = pid;
+	program->next       = NULL;
+	program->reserved   = 0x7;
+
+	if (head) {
+		while (head->next)
+			head = head->next;
+
+		head->next = program;
+	}
+
+	return program;
+}
+
+void
+vidtv_psi_pat_program_destroy(struct vidtv_psi_table_pat_program *p)
+{
+	struct vidtv_psi_table_pat_program *curr = p;
+	struct vidtv_psi_table_pat_program *tmp  = NULL;
+
+	while (curr) {
+		tmp  = curr;
+		curr = curr->next;
+		kfree(tmp);
+	}
+}
+
+void
+vidtv_psi_pat_program_assign(struct vidtv_psi_table_pat *pat,
+			     struct vidtv_psi_table_pat_program *p)
+{
+	/* This function transfers ownership of p to the table */
+
+	u16    program_count                        = 0;
+	struct vidtv_psi_table_pat_program *program = p;
+	struct vidtv_psi_table_pat_program *temp    = pat->program;
+
+	while (program) {
+		++program_count;
+		program = program->next;
+	}
+
+	pat->programs = program_count;
+	pat->program  = p;
+
+	/* Recompute section length */
+	vidtv_psi_pat_table_comp_sec_len(pat);
+
+	/* reassign if the new size is too big */
+	if (pat->header.section_length > MAX_SECTION_LEN)
+		vidtv_psi_pat_program_assign(pat, temp);
+	else
+		vidtv_psi_pat_program_destroy(temp);
+}
+
+void vidtv_psi_pat_table_init(struct vidtv_psi_table_pat *pat,
+			      bool update_version_num,
+			      u16 transport_stream_id)
+{
+	static u8 pat_version;
+
+	pat->header.table_id = 0x0;
+	pat->header.syntax   = 0x1;
+	pat->header.zero     = 0x0;
+	pat->header.one      = 0x03;
+
+	/* transport stream ID, at will */
+	pat->header.id           = cpu_to_be16(transport_stream_id);
+	pat->header.current_next = 0x1;
+
+	/* ETSI 300 468: indicates changes in the TS described by this table*/
+	if (update_version_num)
+		++pat_version;
+
+	pat->header.version = pat_version;
+
+	pat->header.one2         = 0x03;
+	pat->header.section_id   = 0x0;
+	pat->header.last_section = 0x0;
+
+	pat->programs = 0;
+
+	vidtv_psi_pat_table_comp_sec_len(pat);
+}
+
+u32 vidtv_psi_pat_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_pat *pat,
+			     u32 buf_sz,
+			     u8 *continuity_counter)
+{
+	/* the number of bytes written by this function */
+	u32   nbytes      = 0;
+	const u16 pat_pid = VIDTV_PAT_PID;
+
+	struct vidtv_psi_table_pat_program *p = pat->program;
+	struct header_write_args h_args       = {};
+	struct psi_write_args args            = {};
+	struct crc32_write_args c_args        = {};
+
+	vidtv_psi_pat_table_comp_sec_len(pat);
+
+	h_args.dest_buf           = buf;
+	h_args.dest_offset        = offset;
+	h_args.h                  = &pat->header;
+	h_args.pid                = pat_pid;
+	h_args.continuity_counter = continuity_counter;
+	h_args.dest_buf_sz        = buf_sz;
+
+	nbytes += vidtv_psi_table_header_write_into(h_args);
+
+	/* note that the field 'u16 programs' is not really part of the PAT */
+
+	args.dest_buf           = buf;
+	args.pid                = pat_pid;
+	args.new_psi_section    = false;
+	args.continuity_counter = continuity_counter;
+	args.is_crc             = false;
+	args.dest_buf_sz        = buf_sz;
+
+	while (p) {
+		/* copy the PAT programs */
+		args.from = p;
+		/* skip the pointer */
+		args.len = sizeof(*p) -
+			   sizeof(struct vidtv_psi_table_pat_program *);
+		args.dest_offset = offset + nbytes;
+
+		nbytes += vidtv_psi_ts_psi_write_into(args);
+
+		p = p->next;
+	}
+
+	c_args.dest_buf           = buf;
+	c_args.dest_offset        = offset + nbytes;
+	c_args.pid                = pat_pid;
+	c_args.continuity_counter = continuity_counter;
+	c_args.dest_buf_sz        = buf_sz;
+
+	nbytes += table_section_crc32_write_into(c_args);
+
+	return nbytes;
+}
+
+void
+vidtv_psi_pat_table_destroy(struct vidtv_psi_table_pat *p)
+{
+	vidtv_psi_pat_program_destroy(p->program);
+}
+
+struct vidtv_psi_table_pmt_stream*
+vidtv_psi_pmt_stream_init(struct vidtv_psi_table_pmt_stream *head,
+			  enum vidtv_psi_stream_types stream_type,
+			  u16 es_pid)
+{
+	struct vidtv_psi_table_pmt_stream *stream;
+
+	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
+
+	stream->type           = stream_type;
+	stream->elementary_pid = es_pid;
+	stream->reserved       = 0x07;
+
+	stream->desc_length = vidtv_psi_desc_comp_len(stream->descriptor);
+
+	stream->zero      = 0x0;
+	stream->reserved2 = 0x0f;
+
+	if (head) {
+		while (head->next)
+			head = head->next;
+
+		head->next = stream;
+	}
+
+	return stream;
+}
+
+void vidtv_psi_pmt_stream_destroy(struct vidtv_psi_table_pmt_stream *s)
+{
+	struct vidtv_psi_table_pmt_stream *curr_stream = s;
+	struct vidtv_psi_table_pmt_stream *tmp_stream  = NULL;
+
+	while (curr_stream) {
+		tmp_stream  = curr_stream;
+		curr_stream = curr_stream->next;
+		kfree(tmp_stream);
+	}
+}
+
+void vidtv_psi_pmt_stream_assign(struct vidtv_psi_table_pmt *pmt,
+				 struct vidtv_psi_table_pmt_stream *s)
+{
+	/* This function transfers ownership of s to the table */
+	struct vidtv_psi_table_pmt_stream *stream = s;
+	struct vidtv_psi_desc *desc               = s->descriptor;
+	struct vidtv_psi_table_pmt_stream *temp   = pmt->stream;
+
+	while (stream)
+		stream = stream->next;
+
+	while (desc)
+		desc = desc->next;
+
+	pmt->stream = s;
+	/* Recompute section length */
+	vidtv_psi_pmt_table_comp_sec_len(pmt);
+
+	/* reassign if the new size is too big */
+	if (pmt->header.section_length > MAX_SECTION_LEN)
+		vidtv_psi_pmt_stream_assign(pmt, temp);
+	else
+		vidtv_psi_pmt_stream_destroy(temp);
+}
+
+u16 vidtv_psi_pmt_get_pid(struct vidtv_psi_table_pmt *section,
+			  struct vidtv_psi_table_pat *pat)
+{
+	struct vidtv_psi_table_pat_program *program = pat->program;
+
+	/*
+	 * service_id is the same as program_number in the
+	 * corresponding program_map_section
+	 * see ETSI EN 300 468 v1.15.1 p. 24
+	 */
+	while (program) {
+		if (program->service_id == section->header.id)
+			return pat->program->pid;
+
+		program = program->next;
+	}
+
+	return TS_LAST_VALID_PID + 1; /* not found */
+}
+
+void vidtv_psi_pmt_table_init(struct vidtv_psi_table_pmt *pmt,
+			      bool update_version_num,
+			      u16 program_number,
+			      u16 pcr_pid)
+{
+	static u8 pmt_version;
+
+	pmt->header.table_id = 0x2;
+	pmt->header.syntax   = 0x1;
+	pmt->header.zero     = 0x0;
+	pmt->header.one      = 0x3;
+
+	pmt->header.id           = cpu_to_be16(program_number);
+	pmt->header.current_next = 0x1;
+
+	/* ETSI 300 468: indicates changes in the TS described by this table*/
+	if (update_version_num)
+		++pmt_version;
+
+	pmt->header.version = pmt_version;
+
+	pmt->header.one2         = 0x3;
+	pmt->header.section_id   = 0;
+	pmt->header.last_section = 0;
+
+	pmt->pcr_pid   = (pcr_pid) ? pcr_pid : 0x1fff;
+	pmt->reserved2 = 0x03;
+
+	pmt->reserved3 = 0x0f;
+	pmt->zero3     = 0x0;
+
+	pmt->desc_length = vidtv_psi_desc_comp_len(pmt->descriptor);
+
+	vidtv_psi_pmt_table_comp_sec_len(pmt);
+}
+
+u32 vidtv_psi_pmt_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_pmt *pmt,
+			     u16 pid,
+			     u32 buf_sz,
+			     u8 *continuity_counter)
+{
+	/* the number of bytes written by this function */
+	u32    nbytes                             = 0;
+	struct vidtv_psi_desc *table_descriptor   = pmt->descriptor;
+	struct vidtv_psi_table_pmt_stream *stream = pmt->stream;
+	struct vidtv_psi_desc *stream_descriptor  = (stream) ?
+						    pmt->stream->descriptor :
+						    NULL;
+
+	struct header_write_args h_args = {};
+	struct psi_write_args args      = {};
+	struct desc_write_args d_args   = {};
+	struct crc32_write_args c_args  = {};
+
+	vidtv_psi_pmt_table_comp_sec_len(pmt);
+
+	h_args.dest_buf           = buf;
+	h_args.dest_offset        = offset;
+	h_args.h                  = &pmt->header;
+	h_args.pid                = pid;
+	h_args.continuity_counter = continuity_counter;
+	h_args.dest_buf_sz        = buf_sz;
+
+	nbytes += vidtv_psi_table_header_write_into(h_args);
+
+	/* write the two bitfields */
+	args.dest_buf = buf;
+	args.from     = pmt + sizeof(struct vidtv_psi_table_header);
+	args.len      = sizeof_field(struct vidtv_psi_table_pmt, bitfield) +
+			sizeof_field(struct vidtv_psi_table_pmt, bitfield2);
+	args.dest_offset        = offset + nbytes;
+	args.pid                = pid;
+	args.new_psi_section    = false;
+	args.continuity_counter = continuity_counter;
+	args.is_crc             = false;
+	args.dest_buf_sz        = buf_sz;
+
+	nbytes += vidtv_psi_ts_psi_write_into(args);
+
+	while (table_descriptor) {
+		/* write the descriptors, if any */
+		d_args.dest_buf           = buf;
+		d_args.dest_offset        = offset + nbytes;
+		d_args.desc               = table_descriptor;
+		d_args.pid                = pid;
+		d_args.continuity_counter = continuity_counter;
+		d_args.dest_buf_sz        = buf_sz;
+
+		nbytes += vidtv_psi_desc_write_into(d_args);
+
+		table_descriptor = table_descriptor->next;
+	}
+
+	while (stream) {
+		/* write the streams, if any */
+		args.from = stream;
+		args.len  = sizeof_field(struct vidtv_psi_table_pmt_stream,
+					 type) +
+			    sizeof_field(struct vidtv_psi_table_pmt_stream,
+					 bitfield) +
+			    sizeof_field(struct vidtv_psi_table_pmt_stream,
+					 bitfield2);
+		args.dest_offset = offset + nbytes;
+
+		nbytes += vidtv_psi_ts_psi_write_into(args);
+
+		while (stream_descriptor) {
+			/* write the stream descriptors, if any */
+			d_args.desc        = stream_descriptor;
+			d_args.dest_offset = offset + nbytes;
+
+			nbytes += vidtv_psi_desc_write_into(d_args);
+
+			stream_descriptor = stream_descriptor->next;
+		}
+
+		stream = stream->next;
+	}
+
+	c_args.dest_buf           = buf;
+	c_args.dest_offset        = offset + nbytes;
+	c_args.pid                = pid;
+	c_args.continuity_counter = continuity_counter;
+	c_args.dest_buf_sz        = buf_sz;
+
+	nbytes += table_section_crc32_write_into(c_args);
+
+	return nbytes;
+}
+
+void vidtv_psi_pmt_table_destroy(struct vidtv_psi_table_pmt *pmt)
+{
+	struct vidtv_psi_desc *curr_desc = pmt->descriptor;
+	struct vidtv_psi_desc *tmp_desc  = NULL;
+
+	while (curr_desc) {
+		tmp_desc  = curr_desc;
+		curr_desc = curr_desc->next;
+		vidtv_psi_desc_destroy(tmp_desc);
+		kfree(tmp_desc);
+	}
+
+	vidtv_psi_pmt_stream_destroy(pmt->stream);
+}
+
+void vidtv_psi_sdt_table_init(struct vidtv_psi_table_sdt *sdt,
+			      bool update_version_num,
+			      u16 transport_stream_id)
+{
+	static u8 sdt_version;
+
+	sdt->header.table_id = 0x42;
+
+	sdt->header.one  = 0x3;
+	sdt->header.zero = 0x1;
+	/*
+	 * The PAT, PMT, and CAT all set this to 0.
+	 * Other tables set this to 1.
+	 */
+	sdt->header.syntax = 0x1;
+
+	/*
+	 * This is a 16-bit field which serves as a label for identification
+	 * of the TS, about which the SDT informs, from any other multiplex
+	 * within the delivery system.
+	 */
+	sdt->header.id           = cpu_to_be16(transport_stream_id);
+	sdt->header.current_next = 0x1;
+
+	/* ETSI 300 468: indicates changes in the TS described by this table*/
+	if (update_version_num)
+		++sdt_version;
+
+	sdt->header.version = sdt_version;
+
+	sdt->header.one2         = 0x3;
+	sdt->header.section_id   = 0;
+	sdt->header.last_section = 0;
+
+	sdt->network_id = cpu_to_be16(transport_stream_id);
+	sdt->reserved   = 0xff;
+
+	vidtv_psi_sdt_table_comp_sec_len(sdt);
+}
+
+u32 vidtv_psi_sdt_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_sdt *sdt,
+			     u32 buf_sz,
+			     u8 *continuity_counter)
+{
+	u32 nbytes  = 0;              /* the number of bytes written */
+	u16 sdt_pid = VIDTV_SDT_PID;  /* see ETSI EN 300 468 v1.15.1 p. 11 */
+
+	struct vidtv_psi_table_sdt_service *service = sdt->service;
+	struct vidtv_psi_desc *service_desc = (sdt->service) ?
+					      sdt->service->descriptor :
+					      NULL;
+
+	struct header_write_args h_args = {};
+	struct psi_write_args args      = {};
+	struct desc_write_args d_args   = {};
+	struct crc32_write_args c_args  = {};
+
+	vidtv_psi_sdt_table_comp_sec_len(sdt);
+
+	h_args.dest_buf           = buf;
+	h_args.dest_offset        = offset;
+	h_args.h                  = &sdt->header;
+	h_args.pid                = sdt_pid;
+	h_args.continuity_counter = continuity_counter;
+	h_args.dest_buf_sz        = buf_sz;
+
+	nbytes += vidtv_psi_table_header_write_into(h_args);
+
+	args.dest_buf = buf;
+	args.from     = sdt + sizeof(struct vidtv_psi_table_header);
+
+	args.len      = sizeof_field(struct vidtv_psi_table_sdt, network_id) +
+			sizeof_field(struct vidtv_psi_table_sdt, reserved);
+
+	args.dest_offset        = offset + nbytes;
+	args.pid                = sdt_pid;
+	args.new_psi_section    = false;
+	args.continuity_counter = continuity_counter;
+	args.is_crc             = false;
+	args.dest_buf_sz        = buf_sz;
+
+	/* copy u16 network_id + u8 reserved)*/
+	nbytes += vidtv_psi_ts_psi_write_into(args);
+
+	while (service) {
+		/* copy the services, if any */
+		args.from = service;
+		/* skip both pointers at the end */
+		args.len = sizeof(struct vidtv_psi_table_sdt_service) -
+			   sizeof(struct vidtv_psi_desc *) -
+			   sizeof(struct vidtv_psi_table_sdt_service *);
+		args.dest_offset = offset + nbytes;
+
+		nbytes += vidtv_psi_ts_psi_write_into(args);
+
+		while (service_desc) {
+			/* copy the service descriptors, if any */
+			d_args.dest_buf           = buf;
+			d_args.dest_offset        = offset + nbytes;
+			d_args.desc               = service_desc;
+			d_args.pid                = sdt_pid;
+			d_args.continuity_counter = continuity_counter;
+			d_args.dest_buf_sz        = buf_sz;
+
+			nbytes += vidtv_psi_desc_write_into(d_args);
+
+			service_desc = service_desc->next;
+		}
+
+		service = service->next;
+	}
+
+	c_args.dest_buf           = buf;
+	c_args.dest_offset        = offset + nbytes;
+	c_args.pid                = sdt_pid;
+	c_args.continuity_counter = continuity_counter;
+	c_args.dest_buf_sz        = buf_sz;
+
+	nbytes += table_section_crc32_write_into(c_args);
+
+	return nbytes;
+}
+
+void vidtv_psi_sdt_table_destroy(struct vidtv_psi_table_sdt *sdt)
+{
+	struct vidtv_psi_table_sdt_service *curr_service = sdt->service;
+	struct vidtv_psi_table_sdt_service *tmp_service  = NULL;
+	struct vidtv_psi_desc *curr_desc = (sdt->service) ?
+					   sdt->service->descriptor : NULL;
+	struct vidtv_psi_desc *tmp_desc = NULL;
+
+	while (curr_service) {
+		curr_desc = curr_service->descriptor;
+
+		while (curr_desc) {
+			/* clear all descriptors for the service */
+			tmp_desc  = curr_desc;
+			curr_desc = curr_desc->next;
+			vidtv_psi_desc_destroy(tmp_desc);
+			kfree(tmp_desc);
+		}
+
+		/* then clear the current service */
+		tmp_service  = curr_service;
+		curr_service = curr_service->next;
+		kfree(tmp_service);
+	}
+}
+
+struct vidtv_psi_table_sdt_service
+*vidtv_psi_sdt_service_init(struct vidtv_psi_table_sdt_service *head,
+			    u16 service_id)
+{
+	/*
+	 * if 'head' is attached to a table, caller should recompute
+	 * the section length afterwards at some point
+	 */
+	struct vidtv_psi_table_sdt_service *service;
+
+	service = kzalloc(sizeof(*service), GFP_KERNEL);
+
+	/*
+	 * ETSI 300 468: this is a 16bit field which serves as a label to
+	 * identify this service from any other service within the TS.
+	 * The service id is the same as the program number in the
+	 * corresponding program_map_section
+	 */
+	service->service_id            = cpu_to_be16(service_id);
+	service->EIT_schedule          = 0x0;
+	service->EIT_present_following = 0x0;
+	service->reserved              = 0x3f;        /* all bits on */
+	service->free_CA_mode          = 0x0;         /* not scrambled */
+	service->running_status        = RUNNING;
+
+	if (head) {
+		while (head->next)
+			head = head->next;
+
+		head->next = service;
+	}
+
+	return service;
+}
+
+void
+vidtv_psi_sdt_service_destroy(struct vidtv_psi_table_sdt_service *service)
+{
+	struct vidtv_psi_table_sdt_service *curr = service;
+	struct vidtv_psi_table_sdt_service *tmp  = NULL;
+
+	while (curr) {
+		tmp  = curr;
+		curr = curr->next;
+		kfree(tmp);
+	}
+}
+
+void
+vidtv_psi_sdt_service_assign(struct vidtv_psi_table_sdt *sdt,
+			     struct vidtv_psi_table_sdt_service *service)
+{
+	struct vidtv_psi_table_sdt_service *temp = sdt->service;
+
+	sdt->service = service;
+
+	/* recompute section length */
+	vidtv_psi_sdt_table_comp_sec_len(sdt);
+
+	/* reassign if the new size is too big */
+	if (sdt->header.section_length > MAX_SECTION_LEN)
+		vidtv_psi_sdt_service_assign(sdt, temp);
+	else
+		vidtv_psi_sdt_service_destroy(temp);
+}
+
+void
+vidtv_psi_pmt_create_sec_for_each_pat_entry(struct vidtv_psi_table_pat *pat,
+					    struct vidtv_psi_table_pmt sec[])
+
+{
+	/*
+	 * PMTs contain information about programs. For each program,
+	 * there is one PMT section. This function will create a section
+	 * for each program found in the PAT
+	 */
+	struct vidtv_psi_table_pat_program *program = pat->program;
+	u32    i                                    = 0;
+
+	while (program) {
+		vidtv_psi_pmt_table_init(&sec[i],
+					 false,
+					 be16_to_cpu(sec[i].header.id),
+					 0);
+
+		++i;
+		program = program->next;
+	}
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_psi.h b/drivers/media/test-drivers/vidtv/vidtv_psi.h
new file mode 100644
index 0000000000000..77b616a46757a
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_psi.h
@@ -0,0 +1,415 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This file contains the logic to work with MPEG Program-Specific Information.
+ * These are defined both in ISO/IEC 13818-1 (systems) and ETSI EN 300 468.
+ * PSI is carried in the form of table structures, and although each table might
+ * technically be broken into one or more sections, we do not do this here,
+ * hence 'table' and 'section' are interchangeable for us.
+ *
+ * This code currently supports three tables: PAT, PMT and SDT. These are the
+ * bare minimum to get userspace to recognize our MPEG transport stream. It can
+ * be extended to support more PSI tables in the future.
+ *
+ * A note on endianness: MPEG layout is big-endian, therefore:
+ * - All fields spanning more than a byte must undergo 'cpu_to_beXX()'
+ * - All bitfields must have their ordering reversed if
+ *  __LITTLE_ENDIAN_BITFIELD is defined.
+ *
+ * Written by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_PSI_H
+#define VIDTV_PSI_H
+
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+/*
+ * all section lengths start immediately after the 'section_length' field
+ * see ISO/IEC 13818-1 : 2000 and ETSI EN 300 468 V 1.10.1 for
+ * reference
+ */
+#define PAT_LEN_UNTIL_LAST_SECTION_NUMBER 5
+#define PMT_LEN_UNTIL_PROGRAM_INFO_LENGTH 9
+#define SDT_LEN_UNTIL_RESERVED_FOR_FUTURE_USE 8
+#define MAX_SECTION_LEN 1021
+#define VIDTV_PAT_PID 0
+#define VIDTV_SDT_PID 0x0011
+
+enum vidtv_psi_descriptors {
+	REGISTRATION_DESCRIPTOR	= 0x05,
+	SERVICE_DESCRIPTOR = 0x48,
+};
+
+enum vidtv_psi_stream_types {
+	/* see ISO/IEC 13818-1 2000 p. 48 */
+	STREAM_PRIVATE_DATA = 0x06,
+};
+
+struct vidtv_psi_desc {
+	u8 type;
+	u8 length;
+	struct vidtv_psi_desc *next;
+	u8 data[];
+} __packed;
+
+struct vidtv_psi_desc_service {
+	u8 type;
+	u8 length;
+	struct vidtv_psi_desc *next;
+
+	u8 service_type;
+	char *name;
+	char *name_emph;
+	char *provider;
+	char *provider_emph;
+} __packed;
+
+struct vidtv_psi_desc_registration {
+	u8 type;
+	u8 length;
+	struct vidtv_psi_desc *next;
+
+	/*
+	 * The format_identifier is a 32-bit value obtained from a Registration
+	 * Authority as designated by ISO/IEC JTC 1/SC 29.
+	 */
+	__be32 format_id;
+	/*
+	 * The meaning of additional_identification_info bytes, if any, are
+	 * defined by the assignee of that format_identifier, and once defined
+	 * they shall not change.
+	 */
+	u8 additional_identification_info[];
+} __packed;
+
+struct vidtv_psi_table_header {
+	u8  table_id;
+	union {
+		__be16 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 section_length:12;
+			u8  one:2;
+			u8  zero:1;
+			u8  syntax:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u8  syntax:1;
+			u8  zero:1;
+			u8  one:2;
+			u16 section_length:12;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+
+	__be16 id;			/* TS ID */
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	u8  current_next:1;
+	u8  version:5;
+	u8  one2:2;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	u8  one2:2;
+	u8  version:5;
+	u8  current_next:1;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+	u8  section_id;		/* section_number */
+	u8  last_section;		/* last_section_number */
+} __packed;
+
+struct vidtv_psi_table_pat_program {
+	__be16 service_id;
+	union {
+		__be16 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u8  reserved:3;
+			u16 pid:13;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 pid:13;
+			u8  reserved:3;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+	struct vidtv_psi_table_pat_program *next;
+} __packed;
+
+struct vidtv_psi_table_pat {
+	struct vidtv_psi_table_header header;
+	u16 programs;
+	struct vidtv_psi_table_pat_program *program;
+} __packed;
+
+struct vidtv_psi_table_sdt_service {
+	__be16 service_id;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	u8 EIT_present_following:1;
+	u8 EIT_schedule:1;
+	u8 reserved:6;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	u8 reserved:6;
+	u8 EIT_schedule:1;
+	u8 EIT_present_following:1;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+	union {
+		__be16 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 desc_length:12;
+			u16 free_CA_mode:1;
+			u16 running_status:3;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 running_status:3;
+			u16 free_CA_mode:1;
+			u16 desc_length:12;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+	struct vidtv_psi_desc *descriptor;
+	struct vidtv_psi_table_sdt_service *next;
+} __packed;
+
+struct vidtv_psi_table_sdt {
+	struct vidtv_psi_table_header header;
+	__be16 network_id; /* original_network_id */
+	u8  reserved;
+	struct vidtv_psi_table_sdt_service *service;
+} __packed;
+
+enum service_running_status {
+	RUNNING,
+};
+
+enum service_type {
+	/* see ETSI EN 300 468 v1.15.1 p. 77 */
+	DIGITAL_TELEVISION_SERVICE = 0x1,
+};
+
+struct vidtv_psi_table_pmt_stream {
+	u8 type;
+	union {
+		__be16 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 elementary_pid:13;
+			u16 reserved:3;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 reserved:3;
+			u16 elementary_pid:13;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+	union {
+		__be16 bitfield2;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 desc_length:10;
+			u16 zero:2;
+			u16 reserved2:4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 reserved2:4;
+			u16 zero:2;
+			u16 desc_length:10;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+	struct vidtv_psi_desc *descriptor;
+	struct vidtv_psi_table_pmt_stream *next;
+} __packed;
+
+struct vidtv_psi_table_pmt {
+	struct vidtv_psi_table_header header;
+	union {
+		__be16 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 pcr_pid:13;
+			u16 reserved2:3;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 reserved2:3;
+			u16 pcr_pid:13;
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+
+	union {
+		__be16 bitfield2;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 desc_length:10; /* program_info_length */
+			u16 zero3:2;
+			u16 reserved3:4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 reserved3:4;
+			u16 zero3:2;
+			u16 desc_length:10; /* program_info_length */
+#else
+#error  "Unknown bitfield ordering"
+#endif
+		} __packed;
+	} __packed;
+	struct vidtv_psi_desc *descriptor;
+	struct vidtv_psi_table_pmt_stream *stream;
+} __packed;
+
+/**
+ * struct psi_write_args - Arguments for the PSI packetizer
+ * @dest_buf: The buffer to write into.
+ * @from: PSI data to be copied.
+ * @len: How much to write.
+ * @dest_offset: where to start writing in the dest_buffer.
+ * @pid: TS packet ID.
+ * @new_psi_section: Set when starting a table section.
+ * @continuity_counter: Incremented on every new packet.
+ * @is_crc: Set when writing the CRC at the end.
+ * @dest_buf_sz: The size of the dest_buffer
+ */
+struct psi_write_args {
+	void *dest_buf;
+	void *from;
+	size_t len;
+	u32 dest_offset;
+	u16 pid;
+	bool new_psi_section;
+	u8 *continuity_counter;
+	bool is_crc;
+	u32 dest_buf_sz;
+};
+
+struct desc_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	struct vidtv_psi_desc *desc;
+	u16 pid;
+	u8 *continuity_counter;
+	u32 dest_buf_sz;
+};
+
+struct crc32_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	u16 pid;
+	u8 *continuity_counter;
+	u32 dest_buf_sz;
+};
+
+struct header_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	struct vidtv_psi_table_header *h;
+	u16 pid;
+	u8 *continuity_counter;
+	u32 dest_buf_sz;
+};
+
+struct vidtv_psi_desc *vidtv_psi_desc_init(struct vidtv_psi_desc *head,
+					   u8 type,
+					   u8 length);
+
+void vidtv_psi_pat_table_init(struct vidtv_psi_table_pat *pat,
+			      bool update_version_num,
+			      u16 transport_stream_id);
+
+struct vidtv_psi_table_pat_program*
+vidtv_psi_pat_program_init(struct vidtv_psi_table_pat_program *head,
+			   u16 service_id,
+			   u16 pid);
+
+struct vidtv_psi_table_pmt_stream*
+vidtv_psi_pmt_stream_init(struct vidtv_psi_table_pmt_stream *head,
+			  enum vidtv_psi_stream_types stream_type,
+			  u16 es_pid);
+
+void vidtv_psi_pmt_table_init(struct vidtv_psi_table_pmt *pmt,
+			      bool update_version_num,
+			      u16 program_number,
+			      u16 pcr_pid);
+
+void
+vidtv_psi_sdt_table_init(struct vidtv_psi_table_sdt *sdt,
+			 bool update_version_num,
+			 u16 transport_stream_id);
+
+struct vidtv_psi_table_sdt_service*
+vidtv_psi_sdt_service_init(struct vidtv_psi_table_sdt_service *head,
+			   u16 service_id);
+
+void
+vidtv_psi_desc_destroy(struct vidtv_psi_desc *desc);
+
+void
+vidtv_psi_pat_program_destroy(struct vidtv_psi_table_pat_program *p);
+
+void
+vidtv_psi_pat_table_destroy(struct vidtv_psi_table_pat *p);
+
+void
+vidtv_psi_pmt_stream_destroy(struct vidtv_psi_table_pmt_stream *s);
+
+void
+vidtv_psi_pmt_table_destroy(struct vidtv_psi_table_pmt *pmt);
+
+void
+vidtv_psi_sdt_table_destroy(struct vidtv_psi_table_sdt *sdt);
+
+void
+vidtv_psi_sdt_service_destroy(struct vidtv_psi_table_sdt_service *service);
+
+void
+vidtv_psi_sdt_service_assign(struct vidtv_psi_table_sdt *sdt,
+			     struct vidtv_psi_table_sdt_service *service);
+
+void vidtv_psi_desc_assign(struct vidtv_psi_desc **to,
+			   struct vidtv_psi_desc *desc);
+
+void vidtv_psi_pat_program_assign(struct vidtv_psi_table_pat *pat,
+				  struct vidtv_psi_table_pat_program *p);
+
+void vidtv_psi_pmt_stream_assign(struct vidtv_psi_table_pmt *pmt,
+				 struct vidtv_psi_table_pmt_stream *s);
+void
+vidtv_psi_pmt_create_sec_for_each_pat_entry(struct vidtv_psi_table_pat *pat,
+					    struct vidtv_psi_table_pmt *sec);
+
+u16 vidtv_psi_pmt_get_pid(struct vidtv_psi_table_pmt *section,
+			  struct vidtv_psi_table_pat *pat);
+
+void vidtv_psi_pat_table_comp_sec_len(struct vidtv_psi_table_pat *pat);
+void vidtv_psi_pmt_table_comp_sec_len(struct vidtv_psi_table_pmt *pmt);
+void vidtv_psi_sdt_table_comp_sec_len(struct vidtv_psi_table_sdt *sdt);
+
+u32 vidtv_psi_pat_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_pat *pat,
+			     u32 buf_sz,
+			     u8 *continuity_counter);
+
+u32 vidtv_psi_sdt_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_sdt *sdt,
+			     u32 buf_sz,
+			     u8 *continuity_counter);
+
+u32 vidtv_psi_pmt_write_into(char *buf,
+			     u32 offset,
+			     struct vidtv_psi_table_pmt *pmt,
+			     u16 pid,
+			     u32 buf_sz,
+			     u8 *continuity_counter);
+
+#endif // VIDTV_PSI_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 08/10] media: vidtv: implement a PES packetizer

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Implement the PES logic to convert encoder data into MPEG TS packets.
These TS packets can then be fed into a TS multiplexer and eventually
into userspace.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 .../media/test-drivers/vidtv/vidtv_common.h   |   2 +
 drivers/media/test-drivers/vidtv/vidtv_pes.c  | 450 ++++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_pes.h  | 186 ++++++++
 3 files changed, 638 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
index a3cb303cc7423..1a31973f3ac61 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_common.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -24,4 +24,6 @@ u32 vidtv_memset(void *to,
 		 int c,
 		 size_t len);
 
+u64 vidtv_extract_bits(u64 value, u8 start_bit, u8 nbits);
+
 #endif // VIDTV_COMMON_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_pes.c b/drivers/media/test-drivers/vidtv/vidtv_pes.c
new file mode 100644
index 0000000000000..c8ea83a3cf800
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_pes.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the logic to translate the ES data for one access unit
+ * from an encoder into MPEG TS packets. It does so by first encapsulating it
+ * with a PES header and then splitting it into TS packets.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/types.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_pes.h"
+#include "vidtv_common.h"
+#include "vidtv_ts.h"
+
+#define PRIVATE_STREAM_1_ID 0xbd /* private_stream_1. See SMPTE 302M-2007 p.6 */
+#define PES_HEADER_MAX_STUFFING_BYTES 32
+#define PES_TS_HEADER_MAX_STUFFING_BYTES 182
+
+static u32 vidtv_pes_op_get_regular_len(bool send_pts, bool send_dts)
+{
+	u32 len = 0;
+
+	/* the flags must always be sent */
+	len += sizeof(struct vidtv_pes_optional);
+
+	/* From all optionals, we might send these for now */
+	if (send_pts && send_dts)
+		len += sizeof(struct vidtv_pes_optional_pts_dts);
+	else if (send_pts)
+		len += sizeof(struct vidtv_pes_optional_pts);
+
+	return len;
+}
+
+static u32 vidtv_pes_h_get_regular_len(bool send_pts, bool send_dts)
+{
+	/* PES header length notwithstanding stuffing bytes */
+	u32 len = 0;
+
+	len += sizeof(struct vidtv_mpeg_pes);
+	len += vidtv_pes_op_get_regular_len(send_pts, send_dts);
+
+	return len;
+}
+
+static u32 vidtv_pes_write_header_stuffing(struct vidtv_mpeg_pes *pes_h,
+					   struct pes_header_write_args args)
+{
+	/*
+	 * This is a fixed 8-bit value equal to '1111 1111' that can be inserted
+	 * by the encoder, for example to meet the requirements of the channel.
+	 * It is discarded by the decoder. No more than 32 stuffing bytes shall
+	 * be present in one PES packet header.
+	 */
+	if (args.n_pes_h_s_bytes > PES_HEADER_MAX_STUFFING_BYTES) {
+		pr_warn_ratelimited("More than 32 stuffing bytes in PES packet header\n");
+		args.n_pes_h_s_bytes = PES_HEADER_MAX_STUFFING_BYTES;
+	}
+
+	/* gives the length of the remainder of the PES header in bytes */
+	pes_h->length += args.n_pes_h_s_bytes;
+
+	return vidtv_memset(args.dest_buf,
+			    args.dest_offset,
+			    args.dest_buf_sz,
+			    TS_FILL_BYTE,
+			    args.n_pes_h_s_bytes);
+}
+
+static u32 vidtv_pes_write_pts_dts(struct pes_header_write_args args)
+{
+	u32 nbytes = 0;  /* the number of bytes written by this function */
+
+	struct vidtv_pes_optional_pts pts         = {};
+	struct vidtv_pes_optional_pts_dts pts_dts = {};
+	void   *op                                = NULL;
+	size_t op_sz                              = 0;
+
+	if (!args.send_pts && args.send_dts)
+		return 0;
+
+	/* see ISO/IEC 13818-1 : 2000 p. 32 */
+
+	if (args.send_pts && args.send_dts) {
+		pts_dts.three = 0x3;
+
+		pts_dts.pts1    = (args.pts & GENMASK(32, 30)) >> 30;
+		pts_dts.marker1 = 0x1;
+		pts_dts.pts2    = (args.pts & GENMASK(29, 15)) >> 15;
+		pts_dts.marker2 = 0x1;
+		pts_dts.pts3    = args.pts & GENMASK(14, 0);
+		pts_dts.marker3 = 0x1;
+
+		pts_dts.one = 0x1;
+
+		pts_dts.dts1    = (args.dts & GENMASK(32, 30)) >> 30;
+		pts_dts.marker1 = 0x1;
+		pts_dts.dts2    = (args.dts & GENMASK(29, 15)) >> 15;
+		pts_dts.marker2 = 0x1;
+		pts_dts.dts3    = args.dts & GENMASK(14, 0);
+		pts_dts.marker3 = 0x1;
+
+		op    = &pts_dts;
+		op_sz = sizeof(pts_dts);
+
+	} else if (args.send_pts) {
+		pts.two     = 0x2;
+		pts_dts.pts1    = (args.pts & GENMASK(32, 30)) >> 30;
+		pts_dts.marker1 = 0x1;
+		pts_dts.pts2    = (args.pts & GENMASK(29, 15)) >> 15;
+		pts_dts.marker2 = 0x1;
+		pts_dts.pts3    = args.pts & GENMASK(14, 0);
+		pts_dts.marker3 = 0x1;
+
+		op    = &pts;
+		op_sz = sizeof(pts);
+	}
+
+	/* copy PTS/DTS optional */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.dest_buf_sz,
+			       op,
+			       op_sz);
+
+	return nbytes;
+}
+
+static u32 vidtv_pes_write_h(struct pes_header_write_args args)
+{
+	u32 nbytes = 0;  /* the number of bytes written by this function */
+
+	struct vidtv_mpeg_pes pes_header          = {};
+	struct vidtv_pes_optional pes_optional    = {};
+	struct pes_header_write_args pts_dts_args = args;
+
+	pes_header.packet_start_code_prefix = PES_START_CODE_PREFIX;
+
+	pes_header.stream_id = (args.is_s302m_pkt) ?
+				PRIVATE_STREAM_1_ID :
+				args.stream_id;
+
+	pes_header.length = vidtv_pes_op_get_regular_len(args.send_pts,
+							 args.send_dts);
+
+	pes_optional.two     = 0x2;
+
+	pes_optional.PTS_DTS = (args.send_pts && args.send_dts) ?
+			       0x3 :
+			       (args.send_pts) ?
+			       0x2 :
+			       0x0;
+
+	/* copy header */
+
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.dest_buf_sz,
+			       &pes_header,
+			       sizeof(pes_header));
+
+	/* copy optional header */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.dest_buf_sz,
+			       &pes_optional,
+			       sizeof(pes_optional));
+
+	pts_dts_args.dest_offset  = args.dest_offset + nbytes;
+	nbytes                   += vidtv_pes_write_pts_dts(pts_dts_args);
+
+	/* write any PES header stuffing */
+	nbytes += vidtv_pes_write_header_stuffing(&pes_header, args);
+
+	return nbytes;
+}
+
+static u32 vidtv_pes_write_stuffing(struct vidtv_mpeg_ts *ts_h,
+				    void *dest_buf,
+				    u32 dest_offset,
+				    u32 n_stuffing_bytes,
+				    u32 buf_sz)
+{
+	/*
+	 * For Transport Stream packets carrying PES packets, stuffing is
+	 * needed when there is insufficient PES packet data to completely
+	 * fill the Transport Stream packet payload bytes. Stuffing is
+	 * accomplished by defining an adaptation field longer than the sum of
+	 * the lengths of the data elements in it, so that the payload bytes
+	 * remaining after the adaptation field exactly accommodates the
+	 * available PES packet data. The extra space in the adaptation field
+	 * is filled with stuffing bytes.
+	 *
+	 */
+
+	/* the number of bytes written by this function */
+	u32    nbytes                         = 0;
+	struct vidtv_mpeg_ts_adaption ts_adap = {};
+
+	if (!n_stuffing_bytes)
+		return nbytes;
+
+	ts_h->adaptation_field = 1;
+
+	if (n_stuffing_bytes > PES_TS_HEADER_MAX_STUFFING_BYTES) {
+		pr_warn_ratelimited("More than %d stuffing bytes for a PES packet",
+				    PES_TS_HEADER_MAX_STUFFING_BYTES);
+
+		n_stuffing_bytes = PES_TS_HEADER_MAX_STUFFING_BYTES;
+	}
+
+	/* the AF will only be its 'length' field with a value of zero */
+	if (n_stuffing_bytes == 1) {
+		nbytes += vidtv_memset(dest_buf,
+				       dest_offset + nbytes,
+				       buf_sz,
+				       0,
+				       n_stuffing_bytes);
+
+		return nbytes;
+	}
+
+	n_stuffing_bytes -= sizeof(ts_adap);
+
+	/* length _immediately_ following 'adaptation_field_length' */
+	ts_adap.length = sizeof(ts_adap) -
+			 sizeof(ts_adap.length) +
+			 n_stuffing_bytes;
+
+	/* write the adap after the TS header */
+	nbytes += vidtv_memcpy(dest_buf,
+			       dest_offset + nbytes,
+			       buf_sz,
+			       &ts_adap,
+			       sizeof(ts_adap));
+
+	/* write the stuffing bytes */
+	nbytes += vidtv_memset(dest_buf,
+			       dest_offset + nbytes,
+			       buf_sz,
+			       TS_FILL_BYTE,
+			       n_stuffing_bytes);
+
+	return nbytes;
+}
+
+static u32 vidtv_pes_write_ts_h(struct pes_ts_header_write_args args)
+{
+	/* number of bytes written by this function */
+	u32    nbytes                  = 0;
+	struct vidtv_mpeg_ts ts_header = {};
+
+	ts_header.sync_byte        = TS_SYNC_BYTE;
+	ts_header.tei              = 0;
+	ts_header.pid              = args.pid;
+	ts_header.priority         = 0;
+	ts_header.scrambling       = 0;             /* not scrambled */
+	ts_header.adaptation_field = 0;
+	ts_header.payload          = 1;
+
+	ts_header.payload_start      = (!args.wrote_pes_header) ? 1 : 0;
+	ts_header.continuity_counter = *args.continuity_counter;
+
+	/*
+	 * This will trigger a discontinuity if the buffer is full, which is
+	 * what we want: the continuity counter will be incremented but nothing
+	 * will get copied by vidtv_memcpy/vidtv_memset, effectively dropping
+	 * the packet.
+	 */
+	vidtv_ts_inc_cc(args.continuity_counter);
+
+	/* write the TS header */
+	nbytes += vidtv_memcpy(args.dest_buf,
+			       args.dest_offset + nbytes,
+			       args.dest_buf_sz,
+			       &ts_header,
+			       sizeof(ts_header));
+
+	/* write stuffing, if any */
+	nbytes += vidtv_pes_write_stuffing(&ts_header,
+					   args.dest_buf,
+					   args.dest_offset + nbytes,
+					   args.n_stuffing_bytes,
+					   args.dest_buf_sz);
+
+	return nbytes;
+}
+
+u32 vidtv_pes_write_into(struct pes_write_args args)
+{
+	u32 nbytes_past_boundary = (args.dest_offset % TS_PACKET_LEN);
+	bool aligned = (nbytes_past_boundary == 0);
+
+	struct pes_ts_header_write_args ts_header_args = {};
+	struct pes_header_write_args pes_header_args   = {};
+
+	/* number of bytes written by this function */
+	u32 nbytes        = 0;
+	u32 remaining_len = args.access_unit_len;
+
+	bool wrote_pes_header = false;
+
+	/* whether we need to stuff the TS packet to align the buffer */
+	bool stuff            = false;
+
+	u32 available_space    = 0;
+	u32 payload_write_len  = 0;
+	u32 num_stuffing_bytes = 0;
+
+	/* Just a sanity check, should not really happen because we stuff the
+	 * TS packet when we finish writing the PES data, but if this happens
+	 * then we have messed up the logic somewhere.
+	 *
+	 * Also note that, unlike packets for PSI data, we need to carry PES
+	 * packets aligned with the payload of transport packets, that is the
+	 * first byte of each PES header must be the first byte in the payload
+	 * of a transport packet. As a consequence, the last byte of a PES
+	 * packet must be the last byte of the payload of a transport packet.
+	 */
+	if (!aligned) {
+		pr_warn_ratelimited("Cannot start a PES packet in a misaligned buffer\n");
+
+		/* forcibly align and hope for the best */
+		nbytes += vidtv_memset(args.dest_buf,
+				       args.dest_offset + nbytes,
+				       args.dest_buf_sz,
+				       TS_FILL_BYTE,
+				       TS_PACKET_LEN - nbytes_past_boundary);
+
+		aligned = true;
+	}
+
+	if (args.send_dts && !args.send_pts) {
+		pr_warn_ratelimited("forbidden value '01' for PTS_DTS flags\n");
+		args.send_pts = true;
+		args.pts      = args.dts;
+	}
+
+	/* see SMPTE 302M clause 6.4 */
+	if (args.is_s302m_pkt) {
+		args.send_dts = false;
+		args.send_pts = true;
+	}
+
+	while (remaining_len) {
+		/*
+		 * The amount of space initially available in the TS packet.
+		 * if this is the beginning of the PES packet, we need to
+		 * take into account the space needed for the TS header _and_
+		 * for the PES header
+		 */
+		available_space = (!wrote_pes_header) ?
+				  TS_PAYLOAD_LEN -
+				  vidtv_pes_h_get_regular_len(args.send_pts,
+							      args.send_dts) :
+				  TS_PAYLOAD_LEN;
+
+		/* if the encoder has inserted stuffing bytes in the PES
+		 * header, account for them.
+		 */
+		available_space -= args.n_pes_h_s_bytes;
+
+		/* whether we need to stuff the TS packet to align the buffer */
+		stuff = remaining_len < available_space;
+
+		/*
+		 * how much of the _actual_ payload we should write in this
+		 * packet.
+		 */
+		payload_write_len = (stuff) ?
+				    remaining_len :
+				    available_space;
+
+		num_stuffing_bytes = available_space - payload_write_len;
+
+		/* write ts header */
+		ts_header_args.dest_buf           = args.dest_buf;
+		ts_header_args.dest_offset        = args.dest_offset + nbytes;
+		ts_header_args.dest_buf_sz        = args.dest_buf_sz;
+		ts_header_args.pid                = args.pid;
+		ts_header_args.continuity_counter = args.continuity_counter;
+		ts_header_args.wrote_pes_header   = wrote_pes_header;
+		ts_header_args.n_stuffing_bytes   = num_stuffing_bytes;
+
+		nbytes += vidtv_pes_write_ts_h(ts_header_args);
+
+		if (!wrote_pes_header) {
+			/* write the PES header only once */
+			pes_header_args.dest_buf        = args.dest_buf;
+
+			pes_header_args.dest_offset     = args.dest_offset +
+							  nbytes;
+
+			pes_header_args.dest_buf_sz     = args.dest_buf_sz;
+			pes_header_args.is_s302m_pkt    = args.is_s302m_pkt;
+			pes_header_args.send_pts        = args.send_pts;
+			pes_header_args.pts             = args.pts;
+			pes_header_args.send_dts        = args.send_dts;
+			pes_header_args.dts             = args.dts;
+			pes_header_args.stream_id       = args.stream_id;
+			pes_header_args.n_pes_h_s_bytes = args.n_pes_h_s_bytes;
+
+			nbytes           += vidtv_pes_write_h(pes_header_args);
+			wrote_pes_header  = true;
+		}
+
+		/* write as much of the payload as we possibly can */
+		nbytes += vidtv_memcpy(args.dest_buf,
+				       args.dest_offset + nbytes,
+				       args.dest_buf_sz,
+				       args.from,
+				       payload_write_len);
+
+		args.from        += payload_write_len;
+		args.dest_offset += nbytes;
+
+		/* Sanity check for underflow. Should not really happen. */
+		if (remaining_len - payload_write_len > remaining_len) {
+			pr_err_ratelimited("Underflow detected\n");
+
+			/* recompute the alignment */
+			nbytes_past_boundary = (args.dest_offset + nbytes) %
+						TS_PACKET_LEN;
+
+			/* forcibly align */
+			nbytes += vidtv_memset(args.dest_buf,
+					       args.dest_offset + nbytes,
+					       args.dest_buf_sz,
+					       TS_FILL_BYTE,
+					       TS_PACKET_LEN -
+					       nbytes_past_boundary);
+
+			/* bailing out is the best that we can do */
+			return nbytes;
+		}
+
+		remaining_len -= payload_write_len;
+	}
+
+	return nbytes;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_pes.h b/drivers/media/test-drivers/vidtv/vidtv_pes.h
new file mode 100644
index 0000000000000..f2cf3872db545
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_pes.h
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the logic to translate the ES data for one access unit
+ * from an encoder into MPEG TS packets. It does so by first encapsulating it
+ * with a PES header and then splitting it into TS packets.
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_PES_H
+#define VIDTV_PES_H
+
+#include <asm/byteorder.h>
+#include <linux/types.h>
+
+#include "vidtv_common.h"
+
+#define PES_MAX_LEN 65536 /* Set 'length' to 0 if greater */
+#define PES_START_CODE_PREFIX 0x001 /* 00 00 01 */
+
+struct vidtv_pes_optional_pts {
+	struct {
+	#if defined(__LITTLE_ENDIAN_BITFIELD)
+		u8 marker3:1; /* always 0x1 */
+		u16 pts3:15;
+		u8 marker2:1; /* always 0x1 */
+		u16 pts2:15;
+		u8 marker1:1; /* always 0x1 */
+		u8 pts1:3;
+		u8 two:4; /* always 0010b */
+	#elif defined(__BIG_ENDIAN_BITFIELD)
+		u8 two:4; /* always 0010b */
+		u8 pts1:3;
+		u8 marker1:1; /* always 0x1 */
+		u16 pts2:15;
+		u8 marker2:1; /* always 0x1 */
+		u16 pts3:15;
+		u8 marker3:1; /* always 0x1 */
+	#else
+	#error  "Unknown bit ordering"
+	#endif
+	} __packed;
+} __packed;
+
+struct vidtv_pes_optional_pts_dts {
+	struct {
+	#if defined(__LITTLE_ENDIAN_BITFIELD)
+		u8 marker6:1; /* always 0x1 */
+		u16 dts3:15;
+		u8 marker5:1; /* always 0x1 */
+		u16 dts2:15;
+		u8 marker4:1; /* always 0x1 */
+		u8 dts1:3;
+		u8 one:4; /* always 0001b */
+		u8 marker3:1; /* always 0x1 */
+		u16 pts3:15;
+		u8 marker2:1; /* always 0x1 */
+		u16 pts2:15;
+		u8 marker1:1; /* always 0x1 */
+		u8 pts1:3;
+		u8 three:4; /* always 0011b */
+	#elif defined(__BIG_ENDIAN_BITFIELD)
+		u8 three:4; /* always 0011b */
+		u8 pts1:3;
+		u8 marker1:1; /* always 0x1 */
+		u16 pts2:15;
+		u8 marker2:1; /* always 0x1 */
+		u16 pts3:15;
+		u8 marker3:1; /* always 0x1 */
+		u8 one:4; /* always 0001b */
+		u8 dts1:3;
+		u8 marker4:1; /* always 0x1 */
+		u16 dts2:15;
+		u8 marker5:1; /* always 0x1 */
+		u16 dts3:15;
+		u8 marker6:1; /* always 0x1 */
+	#else
+	#error  "Unknown bit ordering"
+	#endif
+	} __packed;
+} __packed;
+
+struct vidtv_pes_optional {
+	union {
+		__be16 bitfield;
+		struct {
+			u16 two:2; /* always 0x2*/
+			u16 PES_scrambling_control:2;
+			u16 PES_priority:1;
+			u16 data_alignment_indicator:1; /* ununsed for us */
+			u16 copyright:1;
+			u16 original_or_copy:1;
+			u16 PTS_DTS:2;
+			/* These flags show which components are actually
+			 * present in the "optinal fields" in the optinal PES
+			 * header and which are not. Vidtv currently does
+			 * not need any of these.
+			 */
+			u16 ESCR:1;
+			u16 ES_rate:1;
+			u16 DSM_trick_mode:1;
+			u16 additional_copy_info:1;
+			u16 PES_CRC:1;
+			u16 PES_extension:1;
+		} __packed;
+	} __packed;
+	u8 length;
+} __packed;
+
+struct vidtv_mpeg_pes {
+	union {
+		__be32 bitfield;
+		struct {
+			/* These two together make the 32-bit start-code */
+			u32  packet_start_code_prefix:24;
+			u32  stream_id:8;
+		} __packed;
+	} __packed;
+	/* after this field until the end of the PES data payload */
+	u16 length;
+	struct vidtv_pes_optional optional[];
+} __packed;
+
+struct pes_header_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	u32 dest_buf_sz;
+	bool is_s302m_pkt;
+
+	bool send_pts;
+	u64 pts;
+
+	bool send_dts;
+	u64 dts;
+
+	u16 stream_id;
+	/* might be used by an encoder if needed, gets discarded by decoder */
+	u32 n_pes_h_s_bytes;
+};
+
+struct pes_ts_header_write_args {
+	void *dest_buf;
+	u32 dest_offset;
+	u32 dest_buf_sz;
+	u16 pid;
+	u8 *continuity_counter;
+	bool wrote_pes_header;
+	u32 n_stuffing_bytes;
+};
+
+struct pes_write_args {
+	void *dest_buf; /* pointer to a program mux buffer */
+	void *from; /* pointer to the encoder buffer */
+
+	/* the size of one access unit (with any headers it might need) */
+	u32 access_unit_len;
+
+	u32 dest_offset; /* where to start writing in the program mux buffer */
+	u32 dest_buf_sz; /* how big is the program mux buffer */
+	u16 pid; /* TS packet ID */
+
+	/* use SMPTE 302M to packetize the data */
+	bool is_s302m_pkt;
+
+	u8 *continuity_counter; /* incremented for every TS packet */
+
+	/* Examples: Audio streams (0xc0-0xdf), Video streams (0xe0-0xef) */
+	u16 stream_id;
+
+	bool send_pts;
+	u64 pts;
+
+	bool send_dts;
+	u64 dts;
+
+	/* might be used by an encoder if needed, gets discarded by decoder */
+	u32 n_pes_h_s_bytes;
+};
+
+u32 vidtv_pes_write_into(struct pes_write_args args);
+
+#endif // VIDTV_PES_H
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 09/10] media: vidtv: Implement a SMPTE 302M encoder

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Implement a S302M encoder to make it possible to insert PCM audio data
in the generated MPEG Transport Stream.

This shall enable passing an audio signal into userspace so it can be
decoded and played by media software.

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 .../media/test-drivers/vidtv/vidtv_common.h   |   2 +
 .../media/test-drivers/vidtv/vidtv_encoder.h  | 103 +++
 .../media/test-drivers/vidtv/vidtv_s302m.c    | 636 ++++++++++++++++++
 .../media/test-drivers/vidtv/vidtv_s302m.h    | 119 ++++
 4 files changed, 860 insertions(+)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_encoder.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.h

diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
index 1a31973f3ac61..a0480825b23a9 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_common.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -12,6 +12,8 @@
 
 #include <linux/types.h>
 
+#define CLOCK_UNIT_90KHZ 90000
+
 u32 vidtv_memcpy(void *to,
 		 size_t to_offset,
 		 size_t to_size,
diff --git a/drivers/media/test-drivers/vidtv/vidtv_encoder.h b/drivers/media/test-drivers/vidtv/vidtv_encoder.h
new file mode 100644
index 0000000000000..361e49c58c96e
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_encoder.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains a generic encoder type that can provide data for a stream
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_ENCODER_H
+#define VIDTV_ENCODER_H
+
+#include <linux/types.h>
+
+enum vidtv_encoder_id {
+	/* add IDs here when implementing new encoders */
+	S302M,
+};
+
+/**
+ * struct vidtv_encoder - A generic encoder type.
+ * @id: So we can cast to a concrete implementation when needed.
+ * @name: Usually the same as the stream name.
+ * @encoder_buf: The encoder internal buffer for the access units.
+ * @encoder_buf_sz: The encoder buffer size, in bytes
+ * @encoder_buf_offset: Our byte position in the encoder buffer.
+ * @sample_count: How many samples we have encoded in total.
+ * @previous_sample_count: The previous sample count, before clear() was
+ * called.
+ * @nunits: The number of access units ready.
+ * @pts: Array mapping pts[i] for AU[i].
+ * @dts: Array mapping dts[i] for AU[i]
+ * @nbytes: Array mapping how many bytes were written per AU.
+ * @offsets: array keeping track of AU offsets in the buffer.
+ * @src_buf: The source of raw data to be encoded, encoder might set a
+ * default if null.
+ * @src_buf_offset: Our position in the source buffer.
+ * @video: Either video or audio.
+ * @ctx: Encoder-specific state.
+ * @stream_id: Examples: Audio streams (0xc0-0xdf), Video streams
+ * (0xe0-0xef).
+ * @es_id: The TS PID to use for the elementary stream in this encoder.
+ * @encode: Prepare enough AUs for the given amount of time.
+ * @clear: Clear the encoder output.
+ * @sync: Attempt to synchronize with this encoder.
+ * @sampling_rate_hz: The sampling rate (or fps, if video) used.
+ * @access_unit_capacity: Controls allocation for the arrays.
+ * @last_sample_cb: Called when the encoder runs out of data. The encoder
+ * 		    might optionally wrap around the src data if this is not
+ * 		    implemented. This is so the source can read data in a
+ * 		    piecemeal fashion instead of having to
+ * 		    provide it all at once.
+ * @destroy: Destroy this encoder, freeing allocated resources.
+ */
+struct vidtv_encoder {
+	enum vidtv_encoder_id id;
+	char *name;
+
+	u8 *encoder_buf;
+	u32 encoder_buf_sz;
+	u32 encoder_buf_offset;
+
+	u32 sample_count;
+	u32 previous_sample_count;
+
+	u32 nunits;
+	u32 *samples_per_unit;
+	u64 *pts;
+	u64 *dts;
+	u32 *nbytes;
+	u32 *offsets;
+
+	void *src_buf;
+	u32 src_buf_sz;
+	u32 src_buf_offset;
+
+	bool video;
+	void *ctx;
+
+	u16 stream_id;
+
+	u16 es_pid;
+
+	void *(*encode)(struct vidtv_encoder *e, u64 elapsed_time_usecs);
+
+	u8 (*clear)(struct vidtv_encoder *e);
+
+	struct vidtv_encoder *sync;
+
+	u32 sampling_rate_hz;
+
+	u8 access_unit_capacity;
+
+	void (*last_sample_cb)(u32 sample_no);
+
+	void (*destroy)(struct vidtv_encoder *e);
+
+	struct vidtv_encoder *next;
+};
+
+#endif /* VIDTV_ENCODER_H */
diff --git a/drivers/media/test-drivers/vidtv/vidtv_s302m.c b/drivers/media/test-drivers/vidtv/vidtv_s302m.c
new file mode 100644
index 0000000000000..3fc537efd9332
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_s302m.c
@@ -0,0 +1,636 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the code for an AES3 (also known as AES/EBU) encoder.
+ * It is based on EBU Tech 3250 and SMPTE 302M technical documents.
+ *
+ * This encoder currently supports 16bit AES3 subframes using 16bit signed
+ * integers.
+ *
+ * Note: AU stands for Access Unit, and AAU stands for Audio Access Unit
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/crc32.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_s302m.h"
+#include "vidtv_encoder.h"
+#include "vidtv_common.h"
+
+#define S302M_SAMPLING_RATE_HZ 48000
+
+/* see EBU Tech 3250 2004 clause 4 */
+#define CHANNEL_STATUS_BIT_LEN 92
+
+#define S302M_2CHANNELS 0
+#define S302M_BITS_PER_SAMPLE_16 0
+
+/* see preamble definition in EBU Tech 3250 2004 clause 2.4 */
+#define PREAMBLE_X_F0 0xe2 /* sub-frame 1 */
+#define PREAMBLE_Y_F0 0xe4 /* sub-frame 2 */
+#define PREAMBLE_Z_F0 0xe8 /* sub-frame 1 + block start */
+/* F0 and F1 refer to whether the F bit was set in the previous sub-frame */
+#define PREAMBLE_X_F1 0x1d /* sub-frame 1 */
+#define PREAMBLE_Y_F1 0X1b /* sub-frame 2 */
+#define PREAMBLE_Z_F1 0x17 /* sub-frame 1 + block start */
+
+#define S302M_BLOCK_SZ 192
+#define S302M_SIN_LUT_SZ 1024
+
+/*
+ * This buffer contains PCM audio samples of a sine wave, compatible with
+ * S302m
+ */
+static int s302m_sin_lut[S302M_SIN_LUT_SZ] = {
+	0x8000, 0x80c9, 0x8192, 0x825b, 0x8324, 0x83ed, 0x84b6, 0x857e,
+	0x8647, 0x8710, 0x87d9, 0x88a1, 0x896a, 0x8a32, 0x8afb, 0x8bc3,
+	0x8c8b, 0x8d53, 0x8e1b, 0x8ee3, 0x8fab, 0x9072, 0x9139, 0x9201,
+	0x92c7, 0x938e, 0x9455, 0x951b, 0x95e1, 0x96a7, 0x976d, 0x9833,
+	0x98f8, 0x99bd, 0x9a82, 0x9b47, 0x9c0b, 0x9ccf, 0x9d93, 0x9e56,
+	0x9f19, 0x9fdc, 0xa09f, 0xa161, 0xa223, 0xa2e5, 0xa3a6, 0xa467,
+	0xa527, 0xa5e8, 0xa6a7, 0xa767, 0xa826, 0xa8e5, 0xa9a3, 0xaa61,
+	0xab1f, 0xabdc, 0xac98, 0xad55, 0xae10, 0xaecc, 0xaf87, 0xb041,
+	0xb0fb, 0xb1b5, 0xb26e, 0xb326, 0xb3de, 0xb496, 0xb54d, 0xb603,
+	0xb6b9, 0xb76f, 0xb824, 0xb8d8, 0xb98c, 0xba3f, 0xbaf2, 0xbba4,
+	0xbc56, 0xbd07, 0xbdb7, 0xbe67, 0xbf17, 0xbfc5, 0xc073, 0xc121,
+	0xc1cd, 0xc279, 0xc325, 0xc3d0, 0xc47a, 0xc524, 0xc5cc, 0xc675,
+	0xc71c, 0xc7c3, 0xc869, 0xc90f, 0xc9b3, 0xca57, 0xcafb, 0xcb9d,
+	0xcc3f, 0xcce0, 0xcd81, 0xce20, 0xcebf, 0xcf5d, 0xcffb, 0xd097,
+	0xd133, 0xd1ce, 0xd268, 0xd302, 0xd39a, 0xd432, 0xd4c9, 0xd55f,
+	0xd5f5, 0xd689, 0xd71d, 0xd7b0, 0xd842, 0xd8d3, 0xd964, 0xd9f3,
+	0xda82, 0xdb0f, 0xdb9c, 0xdc28, 0xdcb3, 0xdd3d, 0xddc7, 0xde4f,
+	0xded7, 0xdf5d, 0xdfe3, 0xe068, 0xe0eb, 0xe16e, 0xe1f0, 0xe271,
+	0xe2f1, 0xe370, 0xe3ee, 0xe46b, 0xe4e8, 0xe563, 0xe5dd, 0xe656,
+	0xe6cf, 0xe746, 0xe7bc, 0xe831, 0xe8a6, 0xe919, 0xe98b, 0xe9fc,
+	0xea6d, 0xeadc, 0xeb4a, 0xebb7, 0xec23, 0xec8e, 0xecf8, 0xed61,
+	0xedc9, 0xee30, 0xee96, 0xeefa, 0xef5e, 0xefc1, 0xf022, 0xf083,
+	0xf0e2, 0xf140, 0xf19d, 0xf1f9, 0xf254, 0xf2ae, 0xf307, 0xf35e,
+	0xf3b5, 0xf40a, 0xf45f, 0xf4b2, 0xf504, 0xf555, 0xf5a5, 0xf5f3,
+	0xf641, 0xf68d, 0xf6d8, 0xf722, 0xf76b, 0xf7b3, 0xf7fa, 0xf83f,
+	0xf884, 0xf8c7, 0xf909, 0xf94a, 0xf989, 0xf9c8, 0xfa05, 0xfa41,
+	0xfa7c, 0xfab6, 0xfaee, 0xfb26, 0xfb5c, 0xfb91, 0xfbc5, 0xfbf8,
+	0xfc29, 0xfc59, 0xfc88, 0xfcb6, 0xfce3, 0xfd0e, 0xfd39, 0xfd62,
+	0xfd89, 0xfdb0, 0xfdd5, 0xfdfa, 0xfe1d, 0xfe3e, 0xfe5f, 0xfe7e,
+	0xfe9c, 0xfeb9, 0xfed5, 0xfeef, 0xff09, 0xff21, 0xff37, 0xff4d,
+	0xff61, 0xff74, 0xff86, 0xff97, 0xffa6, 0xffb4, 0xffc1, 0xffcd,
+	0xffd8, 0xffe1, 0xffe9, 0xfff0, 0xfff5, 0xfff9, 0xfffd, 0xfffe,
+	0xffff, 0xfffe, 0xfffd, 0xfff9, 0xfff5, 0xfff0, 0xffe9, 0xffe1,
+	0xffd8, 0xffcd, 0xffc1, 0xffb4, 0xffa6, 0xff97, 0xff86, 0xff74,
+	0xff61, 0xff4d, 0xff37, 0xff21, 0xff09, 0xfeef, 0xfed5, 0xfeb9,
+	0xfe9c, 0xfe7e, 0xfe5f, 0xfe3e, 0xfe1d, 0xfdfa, 0xfdd5, 0xfdb0,
+	0xfd89, 0xfd62, 0xfd39, 0xfd0e, 0xfce3, 0xfcb6, 0xfc88, 0xfc59,
+	0xfc29, 0xfbf8, 0xfbc5, 0xfb91, 0xfb5c, 0xfb26, 0xfaee, 0xfab6,
+	0xfa7c, 0xfa41, 0xfa05, 0xf9c8, 0xf989, 0xf94a, 0xf909, 0xf8c7,
+	0xf884, 0xf83f, 0xf7fa, 0xf7b3, 0xf76b, 0xf722, 0xf6d8, 0xf68d,
+	0xf641, 0xf5f3, 0xf5a5, 0xf555, 0xf504, 0xf4b2, 0xf45f, 0xf40a,
+	0xf3b5, 0xf35e, 0xf307, 0xf2ae, 0xf254, 0xf1f9, 0xf19d, 0xf140,
+	0xf0e2, 0xf083, 0xf022, 0xefc1, 0xef5e, 0xeefa, 0xee96, 0xee30,
+	0xedc9, 0xed61, 0xecf8, 0xec8e, 0xec23, 0xebb7, 0xeb4a, 0xeadc,
+	0xea6d, 0xe9fc, 0xe98b, 0xe919, 0xe8a6, 0xe831, 0xe7bc, 0xe746,
+	0xe6cf, 0xe656, 0xe5dd, 0xe563, 0xe4e8, 0xe46b, 0xe3ee, 0xe370,
+	0xe2f1, 0xe271, 0xe1f0, 0xe16e, 0xe0eb, 0xe068, 0xdfe3, 0xdf5d,
+	0xded7, 0xde4f, 0xddc7, 0xdd3d, 0xdcb3, 0xdc28, 0xdb9c, 0xdb0f,
+	0xda82, 0xd9f3, 0xd964, 0xd8d3, 0xd842, 0xd7b0, 0xd71d, 0xd689,
+	0xd5f5, 0xd55f, 0xd4c9, 0xd432, 0xd39a, 0xd302, 0xd268, 0xd1ce,
+	0xd133, 0xd097, 0xcffb, 0xcf5d, 0xcebf, 0xce20, 0xcd81, 0xcce0,
+	0xcc3f, 0xcb9d, 0xcafb, 0xca57, 0xc9b3, 0xc90f, 0xc869, 0xc7c3,
+	0xc71c, 0xc675, 0xc5cc, 0xc524, 0xc47a, 0xc3d0, 0xc325, 0xc279,
+	0xc1cd, 0xc121, 0xc073, 0xbfc5, 0xbf17, 0xbe67, 0xbdb7, 0xbd07,
+	0xbc56, 0xbba4, 0xbaf2, 0xba3f, 0xb98c, 0xb8d8, 0xb824, 0xb76f,
+	0xb6b9, 0xb603, 0xb54d, 0xb496, 0xb3de, 0xb326, 0xb26e, 0xb1b5,
+	0xb0fb, 0xb041, 0xaf87, 0xaecc, 0xae10, 0xad55, 0xac98, 0xabdc,
+	0xab1f, 0xaa61, 0xa9a3, 0xa8e5, 0xa826, 0xa767, 0xa6a7, 0xa5e8,
+	0xa527, 0xa467, 0xa3a6, 0xa2e5, 0xa223, 0xa161, 0xa09f, 0x9fdc,
+	0x9f19, 0x9e56, 0x9d93, 0x9ccf, 0x9c0b, 0x9b47, 0x9a82, 0x99bd,
+	0x98f8, 0x9833, 0x976d, 0x96a7, 0x95e1, 0x951b, 0x9455, 0x938e,
+	0x92c7, 0x9201, 0x9139, 0x9072, 0x8fab, 0x8ee3, 0x8e1b, 0x8d53,
+	0x8c8b, 0x8bc3, 0x8afb, 0x8a32, 0x896a, 0x88a1, 0x87d9, 0x8710,
+	0x8647, 0x857e, 0x84b6, 0x83ed, 0x8324, 0x825b, 0x8192, 0x80c9,
+	0x8000, 0x7f36, 0x7e6d, 0x7da4, 0x7cdb, 0x7c12, 0x7b49, 0x7a81,
+	0x79b8, 0x78ef, 0x7826, 0x775e, 0x7695, 0x75cd, 0x7504, 0x743c,
+	0x7374, 0x72ac, 0x71e4, 0x711c, 0x7054, 0x6f8d, 0x6ec6, 0x6dfe,
+	0x6d38, 0x6c71, 0x6baa, 0x6ae4, 0x6a1e, 0x6958, 0x6892, 0x67cc,
+	0x6707, 0x6642, 0x657d, 0x64b8, 0x63f4, 0x6330, 0x626c, 0x61a9,
+	0x60e6, 0x6023, 0x5f60, 0x5e9e, 0x5ddc, 0x5d1a, 0x5c59, 0x5b98,
+	0x5ad8, 0x5a17, 0x5958, 0x5898, 0x57d9, 0x571a, 0x565c, 0x559e,
+	0x54e0, 0x5423, 0x5367, 0x52aa, 0x51ef, 0x5133, 0x5078, 0x4fbe,
+	0x4f04, 0x4e4a, 0x4d91, 0x4cd9, 0x4c21, 0x4b69, 0x4ab2, 0x49fc,
+	0x4946, 0x4890, 0x47db, 0x4727, 0x4673, 0x45c0, 0x450d, 0x445b,
+	0x43a9, 0x42f8, 0x4248, 0x4198, 0x40e8, 0x403a, 0x3f8c, 0x3ede,
+	0x3e32, 0x3d86, 0x3cda, 0x3c2f, 0x3b85, 0x3adb, 0x3a33, 0x398a,
+	0x38e3, 0x383c, 0x3796, 0x36f0, 0x364c, 0x35a8, 0x3504, 0x3462,
+	0x33c0, 0x331f, 0x327e, 0x31df, 0x3140, 0x30a2, 0x3004, 0x2f68,
+	0x2ecc, 0x2e31, 0x2d97, 0x2cfd, 0x2c65, 0x2bcd, 0x2b36, 0x2aa0,
+	0x2a0a, 0x2976, 0x28e2, 0x284f, 0x27bd, 0x272c, 0x269b, 0x260c,
+	0x257d, 0x24f0, 0x2463, 0x23d7, 0x234c, 0x22c2, 0x2238, 0x21b0,
+	0x2128, 0x20a2, 0x201c, 0x1f97, 0x1f14, 0x1e91, 0x1e0f, 0x1d8e,
+	0x1d0e, 0x1c8f, 0x1c11, 0x1b94, 0x1b17, 0x1a9c, 0x1a22, 0x19a9,
+	0x1930, 0x18b9, 0x1843, 0x17ce, 0x1759, 0x16e6, 0x1674, 0x1603,
+	0x1592, 0x1523, 0x14b5, 0x1448, 0x13dc, 0x1371, 0x1307, 0x129e,
+	0x1236, 0x11cf, 0x1169, 0x1105, 0x10a1, 0x103e, 0xfdd, 0xf7c,
+	0xf1d, 0xebf, 0xe62, 0xe06, 0xdab, 0xd51, 0xcf8, 0xca1,
+	0xc4a, 0xbf5, 0xba0, 0xb4d, 0xafb, 0xaaa, 0xa5a, 0xa0c,
+	0x9be, 0x972, 0x927, 0x8dd, 0x894, 0x84c, 0x805, 0x7c0,
+	0x77b, 0x738, 0x6f6, 0x6b5, 0x676, 0x637, 0x5fa, 0x5be,
+	0x583, 0x549, 0x511, 0x4d9, 0x4a3, 0x46e, 0x43a, 0x407,
+	0x3d6, 0x3a6, 0x377, 0x349, 0x31c, 0x2f1, 0x2c6, 0x29d,
+	0x276, 0x24f, 0x22a, 0x205, 0x1e2, 0x1c1, 0x1a0, 0x181,
+	0x163, 0x146, 0x12a, 0x110, 0xf6, 0xde, 0xc8, 0xb2,
+	0x9e, 0x8b, 0x79, 0x68, 0x59, 0x4b, 0x3e, 0x32,
+	0x27, 0x1e, 0x16, 0xf, 0xa, 0x6, 0x2, 0x1,
+	0x0, 0x1, 0x2, 0x6, 0xa, 0xf, 0x16, 0x1e,
+	0x27, 0x32, 0x3e, 0x4b, 0x59, 0x68, 0x79, 0x8b,
+	0x9e, 0xb2, 0xc8, 0xde, 0xf6, 0x110, 0x12a, 0x146,
+	0x163, 0x181, 0x1a0, 0x1c1, 0x1e2, 0x205, 0x22a, 0x24f,
+	0x276, 0x29d, 0x2c6, 0x2f1, 0x31c, 0x349, 0x377, 0x3a6,
+	0x3d6, 0x407, 0x43a, 0x46e, 0x4a3, 0x4d9, 0x511, 0x549,
+	0x583, 0x5be, 0x5fa, 0x637, 0x676, 0x6b5, 0x6f6, 0x738,
+	0x77b, 0x7c0, 0x805, 0x84c, 0x894, 0x8dd, 0x927, 0x972,
+	0x9be, 0xa0c, 0xa5a, 0xaaa, 0xafb, 0xb4d, 0xba0, 0xbf5,
+	0xc4a, 0xca1, 0xcf8, 0xd51, 0xdab, 0xe06, 0xe62, 0xebf,
+	0xf1d, 0xf7c, 0xfdd, 0x103e, 0x10a1, 0x1105, 0x1169, 0x11cf,
+	0x1236, 0x129e, 0x1307, 0x1371, 0x13dc, 0x1448, 0x14b5, 0x1523,
+	0x1592, 0x1603, 0x1674, 0x16e6, 0x1759, 0x17ce, 0x1843, 0x18b9,
+	0x1930, 0x19a9, 0x1a22, 0x1a9c, 0x1b17, 0x1b94, 0x1c11, 0x1c8f,
+	0x1d0e, 0x1d8e, 0x1e0f, 0x1e91, 0x1f14, 0x1f97, 0x201c, 0x20a2,
+	0x2128, 0x21b0, 0x2238, 0x22c2, 0x234c, 0x23d7, 0x2463, 0x24f0,
+	0x257d, 0x260c, 0x269b, 0x272c, 0x27bd, 0x284f, 0x28e2, 0x2976,
+	0x2a0a, 0x2aa0, 0x2b36, 0x2bcd, 0x2c65, 0x2cfd, 0x2d97, 0x2e31,
+	0x2ecc, 0x2f68, 0x3004, 0x30a2, 0x3140, 0x31df, 0x327e, 0x331f,
+	0x33c0, 0x3462, 0x3504, 0x35a8, 0x364c, 0x36f0, 0x3796, 0x383c,
+	0x38e3, 0x398a, 0x3a33, 0x3adb, 0x3b85, 0x3c2f, 0x3cda, 0x3d86,
+	0x3e32, 0x3ede, 0x3f8c, 0x403a, 0x40e8, 0x4198, 0x4248, 0x42f8,
+	0x43a9, 0x445b, 0x450d, 0x45c0, 0x4673, 0x4727, 0x47db, 0x4890,
+	0x4946, 0x49fc, 0x4ab2, 0x4b69, 0x4c21, 0x4cd9, 0x4d91, 0x4e4a,
+	0x4f04, 0x4fbe, 0x5078, 0x5133, 0x51ef, 0x52aa, 0x5367, 0x5423,
+	0x54e0, 0x559e, 0x565c, 0x571a, 0x57d9, 0x5898, 0x5958, 0x5a17,
+	0x5ad8, 0x5b98, 0x5c59, 0x5d1a, 0x5ddc, 0x5e9e, 0x5f60, 0x6023,
+	0x60e6, 0x61a9, 0x626c, 0x6330, 0x63f4, 0x64b8, 0x657d, 0x6642,
+	0x6707, 0x67cc, 0x6892, 0x6958, 0x6a1e, 0x6ae4, 0x6baa, 0x6c71,
+	0x6d38, 0x6dfe, 0x6ec6, 0x6f8d, 0x7054, 0x711c, 0x71e4, 0x72ac,
+	0x7374, 0x743c, 0x7504, 0x75cd, 0x7695, 0x775e, 0x7826, 0x78ef,
+	0x79b8, 0x7a81, 0x7b49, 0x7c12, 0x7cdb, 0x7da4, 0x7e6d, 0x7f36
+};
+
+static void vidtv_s302m_compute_nunits(struct vidtv_encoder *e)
+{
+	/*
+	 * match the amount of video units if we are trying to sync with a video
+	 * encoder
+	 */
+	if (e->sync && e->sync->video) {
+		e->nunits = e->sync->nunits;
+		return;
+	}
+
+	/* otherwise return enough samples for the timedelta in a single AU */
+	e->nunits = 1;
+}
+
+static void
+vidtv_s302m_compute_sample_count_v(struct vidtv_encoder *e)
+{
+	/* compute sample count for VAU[i] in 'sync' */
+	u32 vau_duration_usecs;
+	u32 sample_duration_usecs;
+	u32 i;
+	u32 s;
+
+	vau_duration_usecs    = USEC_PER_SEC / e->sync->sampling_rate_hz;
+	sample_duration_usecs = USEC_PER_SEC / e->sampling_rate_hz;
+
+	for (i = 0; i < e->sync->nunits; ++i) {
+		s = DIV_ROUND_UP(vau_duration_usecs, sample_duration_usecs);
+		e->samples_per_unit[i] = s;
+	}
+}
+
+static void
+vidtv_s302m_compute_sample_count(struct vidtv_encoder *e,
+				 u64 elapsed_time_usecs)
+{
+	/* compute sample count for 'elapsed_time_usecs' */
+	u32 sample_duration_usecs = USEC_PER_SEC / e->sampling_rate_hz;
+
+	e->samples_per_unit[0] = elapsed_time_usecs / sample_duration_usecs;
+}
+
+static void vidtv_s302m_compute_pts(struct vidtv_encoder *e)
+{
+	u32 count = e->previous_sample_count;
+	u32 i;
+
+	for (i = 0; i < e->nunits; ++i) {
+		count += e->samples_per_unit[i];
+
+		e->pts[i] = count *
+			    CLOCK_UNIT_90KHZ / e->sampling_rate_hz;
+	}
+}
+
+static void vidtv_s302m_compute_pts_v(struct vidtv_encoder *e)
+{
+	u32 i;
+
+	/* use the same pts for video */
+	for (i = 0; i < e->sync->nunits; ++i)
+		e->pts[i] = e->sync->pts[i];
+}
+
+static bool vidtv_s302m_get_c_bit(struct vidtv_encoder *e)
+{
+	/*
+	 * see EBU Tech 3250 2004 clause 5.2.1: minimal implementation of
+	 * channel status
+	 */
+	struct vidtv_s302m_ctx *ctx = e->ctx;
+	bool   start_was_z;
+
+	start_was_z = ctx->last_start_preamble == PREAMBLE_Z_F0 ||
+		      ctx->last_start_preamble == PREAMBLE_Z_F1;
+
+	if (!start_was_z)
+		return false;
+
+	++ctx->current_c_bit;
+
+	/* set the bit only if it is the first C bit after a Z preamble */
+	return !(ctx->current_c_bit % CHANNEL_STATUS_BIT_LEN);
+}
+
+static s16 vidtv_s302m_get_sample(struct vidtv_encoder *e)
+{
+	s16 sample;
+	s16 ret = 0;
+
+	/* bug somewhere */
+	if (e->src_buf_offset > e->src_buf_sz) {
+		pr_err_ratelimited("overflow detected: %d > %d, wrapping.\n",
+				   e->src_buf_offset,
+				   e->src_buf_sz);
+
+		e->src_buf_offset = 0;
+	}
+
+	if (e->src_buf_offset >= e->src_buf_sz) {
+		/* let the source know we are out of data */
+		if (e->last_sample_cb)
+			e->last_sample_cb(e->sample_count);
+
+		e->src_buf_offset = 0;
+	}
+
+	sample = *(s16 *)(e->src_buf + e->src_buf_offset);
+
+	e->sample_count++;
+	e->src_buf_offset += sizeof(s16);
+
+	/* reverse so the LSB comes first when serializing */
+	while (sample) {
+		ret <<= 1;
+
+		if (sample & 1)
+			ret  ^= 1;
+
+		sample >>= 1;
+	}
+
+	return ret;
+}
+
+static void vidtv_s302m_toggle_subframe(struct vidtv_encoder *e)
+{
+	struct vidtv_s302m_ctx *ctx = e->ctx;
+
+	ctx->is_subframe_a = !ctx->is_subframe_a;
+}
+
+static bool vidtv_s302m_is_block_start(const struct vidtv_encoder *e)
+{
+	return e->sample_count % S302M_BLOCK_SZ;
+}
+
+static bool vidtv_s302m_get_f_bit(const struct vidtv_encoder *e)
+{
+	const struct vidtv_s302m_ctx *ctx = e->ctx;
+
+	return vidtv_s302m_is_block_start(e) && ctx->is_subframe_a;
+}
+
+static u8 vidtv_s302m_get_preamble(struct vidtv_encoder *e)
+{
+	/*
+	 * some codecs might disregard the preambles (e.g. ffmpeg s302m), but
+	 * we implement them according to the specs anyway, because some other
+	 * codecs might rely on them.
+	 */
+
+	struct vidtv_s302m_ctx *ctx = e->ctx;
+
+	bool start_was_x = ctx->last_start_preamble == PREAMBLE_X_F0 ||
+			   ctx->last_start_preamble == PREAMBLE_X_F1;
+
+	bool start_was_z = ctx->last_start_preamble == PREAMBLE_Z_F0 ||
+			   ctx->last_start_preamble == PREAMBLE_Z_F1;
+
+	bool is_block_start = vidtv_s302m_is_block_start(e);
+
+	/* bug somewhere: a block always starts with an A subframe */
+	if (!ctx->is_subframe_a && is_block_start) {
+		pr_err_ratelimited("Block should start on 'A' subframe\n");
+		ctx->is_subframe_a = true;
+	}
+
+	if (!ctx->is_subframe_a)
+		return (ctx->last_f) ? PREAMBLE_Y_F1 : PREAMBLE_Y_F0;
+
+	if (start_was_x && is_block_start) {
+		if (ctx->last_f) {
+			ctx->last_start_preamble = PREAMBLE_Z_F0;
+			return PREAMBLE_Z_F0;
+		}
+
+		ctx->last_start_preamble = PREAMBLE_Z_F1;
+		return PREAMBLE_Z_F1;
+	}
+
+	if (start_was_z && is_block_start) {
+		if (ctx->last_f) {
+			ctx->last_start_preamble = PREAMBLE_X_F0;
+			return PREAMBLE_X_F0;
+		}
+
+		ctx->last_start_preamble = PREAMBLE_X_F1;
+		return PREAMBLE_X_F1;
+	}
+
+	return PREAMBLE_X_F0;
+}
+
+static u32 vidtv_s302m_write_subframe(struct vidtv_encoder *e,
+				      struct vidtv_s302m_subframe_16 *f)
+{
+	u32 nbytes = 0;
+
+	nbytes += vidtv_memcpy(e->encoder_buf,
+			       e->encoder_buf_offset,
+			       VIDTV_S302M_BUF_SZ,
+			       f,
+			       sizeof(*f));
+
+	e->encoder_buf_offset += nbytes;
+
+	return nbytes;
+}
+
+static void vidtv_s302m_write_h(struct vidtv_encoder *e, u32 p_sz)
+{
+	struct vidtv_smpte_s302m_es h = {};
+	u32    nbytes                 = 0;
+
+	h.bits_per_sample        = S302M_BITS_PER_SAMPLE_16;
+	h.channel_identification = 0;
+	h.num_channels           = S302M_2CHANNELS;
+	h.audio_packet_size      = p_sz;
+
+	nbytes += vidtv_memcpy(e->encoder_buf,
+			       e->encoder_buf_offset,
+			       e->encoder_buf_sz,
+			       &h,
+			       sizeof(h));
+
+	e->encoder_buf_offset += nbytes;
+}
+
+static void vidtv_s302m_write_frames(struct vidtv_encoder *e)
+{
+	u32    nbytes                    = 0;
+	u32    nbytes_per_unit           = 0;
+	u32    preamble_bit_num          = 0;
+	u32    au_sz                     = 0;
+	struct vidtv_s302m_subframe_16 a = {};
+	struct vidtv_s302m_subframe_16 b = {};
+	u8     preamble_a                = 0; /* four bits sent per subframe */
+	u8     preamble_b                = 0; /* four bits sent per subframe */
+	u8     aux                       = 0;
+	s16    sample                    = 0;
+	bool   v                         = true;
+	bool   u                         = false;
+	bool   c;
+	bool   f;
+
+	u32    i;
+	u32    j;
+
+	for (i = 0; i < e->nunits; ++i) {
+		/* stereo: each sample will generate two subframes */
+		au_sz = e->samples_per_unit[i] *
+			sizeof(struct vidtv_s302m_subframe_16) *
+			2;
+
+		vidtv_s302m_write_h(e, au_sz);
+
+		for (j = 0; j < e->samples_per_unit[i]; ++j) {
+			/* keep this in this order */
+			preamble_a = vidtv_s302m_get_preamble(e);
+			sample     = vidtv_s302m_get_sample(e);
+			c          = vidtv_s302m_get_c_bit(e);
+			f          = vidtv_s302m_get_f_bit(e);
+
+			a.preamble = preamble_bit_num % 8 ?
+				     (preamble_a & GENMASK(3, 0)) :
+				     (preamble_a & GENMASK(7, 4)) >> 4;
+
+			a.aux       = aux;
+			a.data_word = sample;
+			a.v         = v;
+			a.u         = u;
+			a.c         = c;
+			a.f         = f;
+
+			vidtv_s302m_toggle_subframe(e);
+
+			preamble_b = vidtv_s302m_get_preamble(e);
+			c          = vidtv_s302m_get_c_bit(e);
+			f          = vidtv_s302m_get_f_bit(e);
+
+			b.preamble = preamble_bit_num % 8 ?
+				     (preamble_b & GENMASK(3, 0)) :
+				     (preamble_b & GENMASK(7, 4)) >> 4;
+
+			b.aux       = aux;
+			b.data_word = sample;
+			b.v         = v;
+			b.u         = u;
+			b.c         = c;
+			b.f         = f;
+
+			preamble_bit_num += 4;
+
+			nbytes_per_unit += vidtv_s302m_write_subframe(e, &a);
+			nbytes_per_unit += vidtv_s302m_write_subframe(e, &b);
+
+			nbytes += nbytes_per_unit;
+
+			vidtv_s302m_toggle_subframe(e);
+		}
+
+		e->nbytes[i] = nbytes;
+
+		/* did we write more bytes than we initially computed? */
+		if (au_sz != nbytes_per_unit) {
+			pr_warn_ratelimited("write size was %d, expected %d\n",
+					    au_sz,
+					    nbytes_per_unit);
+		}
+
+		e->offsets[i] = nbytes_per_unit;
+		nbytes_per_unit = 0;
+	}
+}
+
+static void *vidtv_s302m_encode(struct vidtv_encoder *e, u64 elapsed_time)
+{
+	/*
+	 * According to SMPTE 302M, an audio access unit is specified as those
+	 * AES3 words that are associated with a corresponding video frame.
+	 * Therefore we should write one AAU for every VAU in the corresponding
+	 * video encoder ('sync'), using the same values for PTS as used by the
+	 * video encoder.
+	 *
+	 * I assume that it is also possible to send audio without any
+	 * associated video, as in a radio-like service. If this is the case,
+	 * we are sending only _one_ AAU with enough audio data for
+	 * 'elapsed_time' instead, computing the value for PTS manually.
+	 */
+
+	vidtv_s302m_compute_nunits(e);
+
+	if (e->sync && e->sync->video) {
+		vidtv_s302m_compute_sample_count_v(e);
+		vidtv_s302m_compute_pts_v(e);
+	} else {
+		vidtv_s302m_compute_sample_count(e, elapsed_time);
+		vidtv_s302m_compute_pts(e);
+	}
+
+	vidtv_s302m_write_frames(e);
+
+	return e->encoder_buf;
+}
+
+static u8 vidtv_s302m_clear(struct vidtv_encoder *e)
+{
+	u8 ret = e->nunits;
+
+	e->nunits = 0;
+	memset(e->samples_per_unit, 0, e->access_unit_capacity);
+	memset(e->nbytes, 0, e->access_unit_capacity);
+	memset(e->offsets, 0, e->access_unit_capacity);
+	memset(e->pts, 0, e->access_unit_capacity);
+	memset(e->dts, 0, e->access_unit_capacity);
+
+	return ret;
+}
+
+struct vidtv_encoder
+*vidtv_s302m_encoder_init(struct vidtv_s302m_encoder_init_args args)
+{
+	struct vidtv_encoder *e = kzalloc(sizeof(*e), GFP_KERNEL);
+	u32    priv_sz          = sizeof(struct vidtv_s302m_ctx);
+
+	if (args.sync)
+		args.access_unit_capacity = args.sync->access_unit_capacity;
+
+	e->id = S302M;
+
+	e->name = kzalloc(strlen(args.name), GFP_KERNEL);
+	strncpy(e->name, args.name, strlen(e->name));
+
+	e->encoder_buf        = vzalloc(VIDTV_S302M_BUF_SZ);
+	e->encoder_buf_sz     = VIDTV_S302M_BUF_SZ;
+	e->encoder_buf_offset = 0;
+
+	e->sample_count          = 0;
+	e->previous_sample_count = 0;
+	e->nunits                = 0;
+
+	e->samples_per_unit = kcalloc(args.access_unit_capacity,
+				      sizeof(u32),
+				      GFP_KERNEL);
+
+	e->pts = kcalloc(args.access_unit_capacity, sizeof(u64), GFP_KERNEL);
+	e->dts = kcalloc(args.access_unit_capacity, sizeof(u64), GFP_KERNEL);
+
+	e->nbytes  = kcalloc(args.access_unit_capacity,
+			     sizeof(u32),
+			     GFP_KERNEL);
+
+	e->offsets = kcalloc(args.access_unit_capacity,
+			     sizeof(u32),
+			     GFP_KERNEL);
+
+	e->src_buf        = (args.src_buf) ? args.src_buf : &s302m_sin_lut;
+	e->src_buf_sz     = (args.src_buf) ? args.src_buf_sz : S302M_SIN_LUT_SZ;
+	e->src_buf_offset = 0;
+
+	e->video = false;
+	e->ctx   = kzalloc(priv_sz, GFP_KERNEL);
+
+	e->encode = vidtv_s302m_encode;
+	e->clear  = vidtv_s302m_clear;
+
+	e->es_pid = args.es_pid;
+
+	e->sync                 = args.sync;
+	e->sampling_rate_hz     = S302M_SAMPLING_RATE_HZ;
+	e->access_unit_capacity = args.access_unit_capacity;
+
+	/* we will wrap around 'src' if this is NULL */
+	e->last_sample_cb = args.last_sample_cb;
+
+	e->destroy = vidtv_s302m_encoder_destroy;
+
+	if (args.head) {
+		while (args.head->next)
+			args.head = args.head->next;
+
+		args.head->next = e;
+	}
+
+	e->next = NULL;
+
+	return e;
+}
+
+void vidtv_s302m_encoder_destroy(struct vidtv_encoder *e)
+{
+	if (e->id != S302M) {
+		pr_err_ratelimited("Encoder type mismatch, skipping.\n");
+		return;
+	}
+
+	kfree(e->name);
+	kfree(e->encoder_buf);
+	kfree(e->samples_per_unit);
+	kfree(e->pts);
+	kfree(e->dts);
+	kfree(e->nbytes);
+	kfree(e->offsets);
+	kfree(e->ctx);
+	kfree(e);
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_s302m.h b/drivers/media/test-drivers/vidtv/vidtv_s302m.h
new file mode 100644
index 0000000000000..d0ed01cffca27
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_s302m.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the code for an AES3 (also known as AES/EBU) encoder.
+ * It is based on EBU Tech 3250 and SMPTE 302M technical documents.
+ *
+ * This encoder currently supports 16bit AES3 subframes using 16bit signed
+ * integers.
+ *
+ * Note: AU stands for Access Unit, and AAU stands for Audio Access Unit
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_S302M_H
+#define VIDTV_S302M_H
+
+#include <linux/types.h>
+#include <asm/byteorder.h>
+
+#include "vidtv_encoder.h"
+
+/* see SMPTE 302M 2007 clause 7.3 */
+#define VIDTV_S302M_BUF_SZ 65024
+
+/* see ETSI TS 102 154 v.1.2.1 clause 7.3.5 */
+#define VIDTV_S302M_FORMAT_IDENTIFIER 0x42535344
+
+/**
+ * struct vidtv_s302m_ctx - s302m encoder context.
+ * @enc: A pointer to the containing encoder structure.
+ * @last_f: whether the F bit was set for the last sub-frame.
+ * @last_start_preamble: The start preamble, either X or Z.
+ * @is_subframe_a: Whether we are writing an A subframe at the moment.
+ * @current_c_bit: The C bit to send in the current subframe.
+ */
+struct vidtv_s302m_ctx {
+	struct vidtv_encoder *enc;
+
+	bool last_f;
+	u8 last_start_preamble;
+	bool is_subframe_a;
+	u8 current_c_bit;
+};
+
+struct vidtv_smpte_s302m_es {
+	union {
+		__be32 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u16 zero:4;
+			u16 bits_per_sample:2; /* 0x0 for 16bits */
+			u16 channel_identification:8;
+			u16 num_channels:2;
+			u16 audio_packet_size:16;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u16 audio_packet_size:16;
+			u16 num_channels:2;
+			u16 channel_identification:8;
+			u16 bits_per_sample:2; /* 0x0 for 16bits */
+			u16 zero:4;
+#else
+#error  "Unknown bit ordering"
+#endif
+		} __packed;
+	} __packed;
+} __packed;
+
+struct vidtv_s302m_subframe_16 {
+	union {
+		u32 bitfield;
+		struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+			u8 f:1;
+			u8 c:1;
+			u8 u:1;
+			u8 v:1;
+			u16 data_word:16; /* little endian */
+			u8 zero:4;
+			u8 aux:4;
+			u8 preamble:4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+			u8 preamble:4;
+			u8 aux:4;
+			u8 zero:4;
+			u16 data_word:16; /* little endian */
+			u8 v:1;
+			u8 u:1;
+			u8 c:1;
+			u8 f:1;
+#else
+#error  "Unknown bit ordering"
+#endif
+		} __packed;
+	} __packed;
+}__packed;
+
+struct vidtv_s302m_encoder_init_args {
+	char *name;
+	void *src_buf;
+	u32 src_buf_sz;
+	u16 es_pid;
+	struct vidtv_encoder *sync;
+	u8 access_unit_capacity;
+	void (*last_sample_cb)(u32 sample_no);
+
+	/* optionally chain to this encoder */
+	struct vidtv_encoder *head;
+};
+
+struct vidtv_encoder
+*vidtv_s302m_encoder_init(struct vidtv_s302m_encoder_init_args args);
+
+void vidtv_s302m_encoder_destroy(struct vidtv_encoder *encoder);
+
+#endif /* VIDTV_S302M_H */
-- 
2.26.2

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[Linux-kernel-mentees] [RFC, WIP, v6 10/10] media: vidtv: Add a MPEG Transport Stream Multiplexer

[Daniel W. S. Almeida]

From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Add a MPEG Transport Stream multiplexer responsible for polling encoders,
interleaving packets, padding the resulting stream with NULL packets if
necessary and then delivering the resulting TS packets to the bridge
driver so it can feed the demux.

This patch includes a "channel" abstraction, which attempts to map a
MPEG service into a struct that vidtv can work with.

When vidtv boots, it will create some hardcoded channels:

-Their services will be concatenated to populate the SDT.
-Their programs will be concatenated to populate the PAT
-For each program in the PAT, a PMT section will be created
-The PMT section for a channel will be assigned its streams.
-Every stream will have its corresponding encoder polled to produce TS packets
-These packets may be interleaved by the mux and then delivered to the bridg

Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
---
 drivers/media/test-drivers/vidtv/Makefile     |   3 +-
 .../media/test-drivers/vidtv/vidtv_bridge.c   |  76 +++
 .../media/test-drivers/vidtv/vidtv_bridge.h   |   2 +
 .../media/test-drivers/vidtv/vidtv_channel.c  | 339 ++++++++++++++
 .../media/test-drivers/vidtv/vidtv_channel.h  |  66 +++
 .../media/test-drivers/vidtv/vidtv_common.h   |   3 +
 drivers/media/test-drivers/vidtv/vidtv_mux.c  | 434 ++++++++++++++++++
 drivers/media/test-drivers/vidtv/vidtv_mux.h  | 105 +++++
 drivers/media/test-drivers/vidtv/vidtv_psi.c  |  18 +
 drivers/media/test-drivers/vidtv/vidtv_psi.h  |   5 +
 10 files changed, 1050 insertions(+), 1 deletion(-)
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.h
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.c
 create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.h

diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
index c99cd13f4adaf..330089e3b70c3 100644
--- a/drivers/media/test-drivers/vidtv/Makefile
+++ b/drivers/media/test-drivers/vidtv/Makefile
@@ -2,7 +2,8 @@
 
 dvb-vidtv-tuner-objs := vidtv_tuner.o
 dvb-vidtv-demod-objs := vidtv_demod.o
-dvb-vidtv-bridge-objs := vidtv_bridge.o
+dvb-vidtv-bridge-objs := vidtv_bridge.o vidtv_common.o vidtv_ts.o vidtv_psi.o \
+			 vidtv_pes.o vidtv_s302m.o vidtv_channel.o vidtv_mux.o
 
 obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o \
 			   dvb-vidtv-bridge.o
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
index bc1c612c23013..6e0589258d52c 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_bridge.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
@@ -20,7 +20,11 @@
 #include "vidtv_bridge.h"
 #include "vidtv_demod.h"
 #include "vidtv_tuner.h"
+#include "vidtv_ts.h"
+#include "vidtv_mux.h"
 
+#define TS_BUF_MAX_SZ (128 * TS_PACKET_LEN)
+#define TS_BUF_MIN_SZ (20 * TS_PACKET_LEN)
 #define TUNER_DEFAULT_ADDR 0x68
 #define DEMOD_DEFAULT_ADDR 0x60
 
@@ -64,6 +68,56 @@ MODULE_PARM_DESC(max_frequency_shift_hz,
 
 DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nums);
 
+/*
+ * Influences the signal acquisition time. See ISO/IEC 13818-1 : 2000. p. 113.
+ */
+static unsigned int si_period_msec = 40;
+module_param(si_period_msec, uint, 0);
+MODULE_PARM_DESC(si_period_msec, "How often to send SI packets. Default: 40ms");
+
+static unsigned int pcr_period_msec = 40;
+module_param(pcr_period_msec, uint, 0);
+MODULE_PARM_DESC(pcr_period_msec, "How often to send PCR packets. Default: 40ms");
+
+static unsigned int mux_rate_kbytes_sec = 4096;
+module_param(mux_rate_kbytes_sec, uint, 0);
+MODULE_PARM_DESC(mux_rate_kbytes_sec, "Mux rate: will pad stream if below");
+
+static unsigned int pcr_pid = 0x200;
+module_param(pcr_pid, uint, 0);
+MODULE_PARM_DESC(pcr_pid, "PCR PID for all channels: defaults to 0x200");
+
+static unsigned int ts_buf_sz_pkts = 20;
+module_param(ts_buf_sz_pkts, uint, 0);
+MODULE_PARM_DESC(ts_buf_sz_pkts, "Size for the TS buffer in multiples of 188 bytes");
+
+static bool vidtv_bridge_check_demod_lock(struct vidtv_dvb *dvb, u32 n)
+{
+	enum fe_status status;
+
+	dvb->fe[n]->ops.read_status(dvb->fe[n], &status);
+
+	return status == (FE_HAS_SIGNAL  |
+			  FE_HAS_CARRIER |
+			  FE_HAS_VITERBI |
+			  FE_HAS_SYNC    |
+			  FE_HAS_LOCK);
+}
+
+static void
+vidtv_bridge_on_new_pkts_avail(void *priv, u8 *buf, u32 npkts)
+{
+	/*
+	 * called on a separate thread by the mux when new packets become
+	 * available
+	 */
+	struct vidtv_dvb *dvb = (struct vidtv_dvb *)priv;
+
+	/* drop packets if we lose the lock */
+	if (vidtv_bridge_check_demod_lock(dvb, 0))
+		dvb_dmx_swfilter_packets(&dvb->demux, buf, npkts);
+}
+
 static int vidtv_start_streaming(struct vidtv_dvb *dvb)
 {
 	if (dvb->streaming) {
@@ -72,12 +126,14 @@ static int vidtv_start_streaming(struct vidtv_dvb *dvb)
 	}
 
 	dvb->streaming = true;
+	vidtv_mux_start_thread(dvb->mux);
 	return 0;
 }
 
 static int vidtv_stop_streaming(struct vidtv_dvb *dvb)
 {
 	dvb->streaming = false;
+	vidtv_mux_stop_thread(dvb->mux);
 
 	return 0;
 }
@@ -340,6 +396,8 @@ static int vidtv_bridge_probe(struct platform_device *pdev)
 {
 	int ret;
 	struct vidtv_dvb *dvb;
+	struct vidtv_mux_init_args mux_args = {0};
+	u32    ts_buf_sz                    = ts_buf_sz_pkts * TS_PACKET_LEN;
 
 	dvb = kzalloc(sizeof(*dvb), GFP_KERNEL);
 	if (!dvb)
@@ -355,6 +413,22 @@ static int vidtv_bridge_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, dvb);
 
+	if (ts_buf_sz < TS_BUF_MIN_SZ)
+		ts_buf_sz = TS_BUF_MIN_SZ;
+
+	if (ts_buf_sz > TS_BUF_MAX_SZ)
+		ts_buf_sz = TS_BUF_MAX_SZ;
+
+	mux_args.mux_rate_kbytes_sec         = mux_rate_kbytes_sec;
+	mux_args.on_new_packets_available_cb = vidtv_bridge_on_new_pkts_avail;
+	mux_args.ts_buf_sz                   = ts_buf_sz;
+	mux_args.pcr_period_usecs            = pcr_period_msec * 1000;
+	mux_args.si_period_usecs             = si_period_msec * 1000;
+	mux_args.pcr_pid                     = pcr_pid;
+	mux_args.priv                        = dvb;
+
+	dvb->mux = vidtv_mux_init(mux_args);
+
 	return ret;
 
 err_dvb:
@@ -369,6 +443,8 @@ static int vidtv_bridge_remove(struct platform_device *pdev)
 
 	dvb = platform_get_drvdata(pdev);
 
+	vidtv_mux_destroy(dvb->mux);
+
 	mutex_destroy(&dvb->feed_lock);
 
 	for (i = 0; i < NUM_FE; ++i)
diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.h b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
index 4931bfb73273c..aac1da13a50aa 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_bridge.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
@@ -18,6 +18,7 @@
 #include <media/dmxdev.h>
 #include <media/dvb_demux.h>
 #include <media/dvb_frontend.h>
+#include "vidtv_mux.h"
 
 struct vidtv_dvb {
 	struct platform_device *pdev;
@@ -34,6 +35,7 @@ struct vidtv_dvb {
 	struct mutex feed_lock; /* start/stop feed */
 
 	bool streaming;
+	struct vidtv_mux *mux;
 };
 
 #endif // VIDTV_BRIDG_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_channel.c b/drivers/media/test-drivers/vidtv/vidtv_channel.c
new file mode 100644
index 0000000000000..c49426f67a680
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_channel.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the code for a 'channel' abstraction.
+ *
+ * When vidtv boots, it will create some hardcoded channels.
+ * Their services will be concatenated to populate the SDT.
+ * Their programs will be concatenated to populate the PAT
+ * For each program in the PAT, a PMT section will be created
+ * The PMT section for a channel will be assigned its streams.
+ * Every stream will have its corresponding encoder polled to produce TS packets
+ * These packets may be interleaved by the mux and then delivered to the bridge
+ *
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+
+#include "vidtv_channel.h"
+#include "vidtv_psi.h"
+#include "vidtv_encoder.h"
+#include "vidtv_mux.h"
+#include "vidtv_common.h"
+#include "vidtv_s302m.h"
+
+static void vidtv_channel_encoder_destroy(struct vidtv_encoder *e)
+{
+	struct vidtv_encoder *curr = e;
+
+	while (curr) {
+		/* forward the call to the derived type */
+		curr->destroy(curr);
+		curr = curr->next;
+	}
+}
+
+static struct vidtv_channel
+*vidtv_channel_s302m_init(struct vidtv_channel *head)
+{
+	/* init an audio only channel with a s302m encoder */
+	const u16 s302m_service_id          = 0x880;
+	const u16 s302m_program_num         = 0x880;
+	const u16 s302m_program_pid         = 0x101; /* packet id for PMT*/
+	const u16 s302m_es_pid              = 0x111; /* packet id for the ES */
+	const u16 s302m_pes_audio_stream_id = 0xbd;  /* PES: private_stream_1 */
+
+	struct vidtv_channel *s302m = kzalloc(sizeof(*s302m), GFP_KERNEL);
+	struct vidtv_psi_table_sdt_service *s302m_service;
+	struct vidtv_psi_desc_service *s302m_s_desc;
+	struct vidtv_s302m_encoder_init_args encoder_args = {};
+
+	s302m_service = vidtv_psi_sdt_service_init(NULL, s302m_service_id);
+
+	s302m_s_desc = (struct vidtv_psi_desc_service *)
+		       vidtv_psi_desc_init(NULL,
+					   SERVICE_DESCRIPTOR,
+					   sizeof(*s302m_s_desc));
+
+	s302m_s_desc->name         = "Sine Wave PCM Audio";
+	s302m_s_desc->service_type = DIGITAL_TELEVISION_SERVICE;
+
+	s302m_s_desc->length = sizeof(s302m_s_desc->service_type)
+			       + strlen(s302m_s_desc->name)
+			       + strlen(s302m_s_desc->name_emph)
+			       + strlen(s302m_s_desc->provider)
+			       + strlen(s302m_s_desc->provider_emph);
+
+	vidtv_psi_desc_assign(&s302m_service->descriptor,
+			      (struct vidtv_psi_desc *)
+			      s302m_s_desc);
+
+	s302m->transport_stream_id = TRANSPORT_STREAM_ID;
+
+	s302m->program = vidtv_psi_pat_program_init(NULL,
+						    s302m_service_id,
+						    s302m_program_pid);
+
+	s302m->program_num = s302m_program_num;
+
+	s302m->streams = vidtv_psi_pmt_stream_init(NULL,
+						   STREAM_PRIVATE_DATA,
+						   s302m_pes_audio_stream_id);
+
+	encoder_args.access_unit_capacity = 16;
+	encoder_args.es_pid               = s302m_es_pid;
+
+	s302m->encoders = vidtv_s302m_encoder_init(encoder_args);
+
+	if (head) {
+		while (head->next)
+			head = head->next;
+
+		head->next = s302m;
+	}
+
+	return s302m;
+}
+
+static struct vidtv_psi_table_sdt_service
+*vidtv_channel_sdt_serv_cat_into_new(struct vidtv_channel *channels)
+{
+	struct vidtv_channel *cur_chnl           = channels;
+	struct vidtv_psi_table_sdt_service *curr = NULL;
+	struct vidtv_psi_table_sdt_service *head = NULL;
+	struct vidtv_psi_table_sdt_service *tail = NULL;
+	u16 service_id;
+
+	while (cur_chnl) {
+		curr       = cur_chnl->service;
+		service_id = be16_to_cpu(curr->service_id);
+
+		if (!curr)
+			continue;
+
+		while (curr->next) {
+			tail = vidtv_psi_sdt_service_init(tail, service_id);
+
+			if (!head)
+				head = tail;
+
+			curr = curr->next;
+		}
+
+		cur_chnl = cur_chnl->next;
+	}
+
+	return head;
+}
+
+static struct vidtv_psi_table_pat_program*
+vidtv_channel_pat_prog_cat_into_new(struct vidtv_channel *channels)
+{
+	struct vidtv_channel *cur_chnl           = channels;
+	struct vidtv_psi_table_pat_program *curr = NULL;
+	struct vidtv_psi_table_pat_program *head = NULL;
+	struct vidtv_psi_table_pat_program *tail = NULL;
+	u16 serv_id;
+
+	while (cur_chnl) {
+		curr = cur_chnl->program;
+
+		if (!curr)
+			continue;
+
+		while (curr->next) {
+			serv_id = be16_to_cpu(curr->service_id);
+			tail = vidtv_psi_pat_program_init(tail,
+							  serv_id,
+							  curr->pid);
+
+			if (!head)
+				head = tail;
+
+			curr = curr->next;
+		}
+
+		cur_chnl = cur_chnl->next;
+	}
+
+	return head;
+}
+
+static void
+vidtv_channel_pmt_match_sections(struct vidtv_channel *channels,
+				 struct vidtv_psi_table_pmt sections[],
+				 u32 nsections)
+{
+	struct vidtv_psi_table_pmt *curr_section = NULL;
+	struct vidtv_channel *cur_chnl           = channels;
+	u32 j;
+	u16 c_id;
+
+	while (cur_chnl) {
+		for (j = 0; j < nsections; ++j) {
+			curr_section = &sections[j];
+
+			if (!curr_section)
+				continue;
+
+			c_id = be16_to_cpu(curr_section->header.id);
+
+			/* we got a match */
+			if (c_id == cur_chnl->program_num) {
+				vidtv_psi_pmt_stream_assign(curr_section,
+							    cur_chnl->streams);
+				break;
+			}
+		}
+
+		cur_chnl = cur_chnl->next;
+	}
+}
+
+void vidtv_channel_si_init(struct vidtv_mux *m)
+{
+	struct vidtv_psi_table_pat *pat = m->si.pat;
+	struct vidtv_psi_table_sdt *sdt = m->si.sdt;
+
+	struct vidtv_psi_table_pmt *pmt_sections = m->si.pmt_secs;
+
+	struct vidtv_psi_table_pat_program *programs = NULL;
+	struct vidtv_psi_table_sdt_service *services = NULL;
+
+	bool update_version_num = false;
+
+	vidtv_psi_pat_table_init(pat,
+				 update_version_num,
+				 TRANSPORT_STREAM_ID);
+
+	vidtv_psi_sdt_table_init(sdt,
+				 update_version_num,
+				 TRANSPORT_STREAM_ID);
+
+	programs = vidtv_channel_pat_prog_cat_into_new(m->channels);
+	services = vidtv_channel_sdt_serv_cat_into_new(m->channels);
+
+	/* assemble all programs and assign to PAT */
+	vidtv_psi_pat_program_assign(pat, programs);
+
+	/* assemble all services and assign to SDT */
+	vidtv_psi_sdt_service_assign(sdt, services);
+
+	/* a section for each program_id */
+	pmt_sections = kcalloc(pat->programs,
+			       sizeof(struct vidtv_psi_table_pmt),
+			       GFP_KERNEL);
+
+	vidtv_psi_pmt_create_sec_for_each_pat_entry(pat,
+						    pmt_sections);
+
+	vidtv_channel_pmt_match_sections(m->channels,
+					 pmt_sections,
+					 pat->programs);
+}
+
+void vidtv_channel_si_destroy(struct vidtv_mux *m)
+{
+	u32 i;
+
+	vidtv_psi_pat_table_destroy(m->si.pat);
+
+	for (i = 0; i < m->si.num_pmt_sections; ++i)
+		vidtv_psi_pmt_table_destroy(&m->si.pmt_secs[i]);
+
+	kfree(m->si.pmt_secs);
+	vidtv_psi_sdt_table_destroy(m->si.sdt);
+}
+
+void vidtv_channels_init(struct vidtv_mux *m)
+{
+	/* we only have a single channel for now */
+	m->channels = vidtv_channel_s302m_init(NULL);
+}
+
+void vidtv_channels_destroy(struct vidtv_mux *m)
+{
+	struct vidtv_channel *curr = m->channels;
+
+	while (curr) {
+		vidtv_psi_sdt_service_destroy(curr->service);
+		vidtv_psi_pat_program_destroy(curr->program);
+		vidtv_psi_pmt_stream_destroy(curr->streams);
+		vidtv_channel_encoder_destroy(curr->encoders);
+		curr = curr->next;
+	}
+}
+
+static void
+vidtv_channels_add_registration_s302m(struct vidtv_psi_table_pmt *sec)
+{
+	struct vidtv_psi_desc_registration *s302m_r_desc;
+
+	/* there might be some descriptors there already */
+	struct vidtv_psi_desc *parent = sec->descriptor;
+
+	s302m_r_desc = (struct vidtv_psi_desc_registration *)
+			vidtv_psi_desc_init(parent,
+					    REGISTRATION_DESCRIPTOR,
+					    sizeof(*s302m_r_desc));
+
+	s302m_r_desc->format_id = cpu_to_be32(VIDTV_S302M_FORMAT_IDENTIFIER);
+
+	if (!parent)
+		vidtv_psi_desc_assign(&sec->descriptor,
+				      (struct vidtv_psi_desc *)s302m_r_desc);
+
+	/* we are adding to the table, so recompute the length */
+	vidtv_psi_pmt_table_comp_sec_len(sec);
+}
+
+void vidtv_channels_add_registration_descs(struct vidtv_mux *m)
+{
+	/*
+	 * Some formats might need a registration descriptor to be recognized.
+	 * S302M needs it, and ffmpeg actually checks for it, so add such
+	 * descriptor at the PMT section that contains the stream
+	 */
+	struct vidtv_channel *cur_chnl  = m->channels;
+	struct vidtv_encoder *e         = NULL;
+	struct vidtv_psi_table_pmt *sec = NULL;
+
+	while (cur_chnl) {
+		e   = cur_chnl->encoders;
+		sec = vidtv_psi_find_pmt_sec(m->si.pmt_secs,
+					     m->si.pat->programs,
+					     cur_chnl->program_num);
+
+		/* bug somewhere */
+		if (!sec) {
+			pr_warn_ratelimited("No section for prog_num %d\n",
+					    cur_chnl->program_num);
+
+			continue;
+		}
+
+		while (e) {
+			switch (e->id) {
+			case S302M:
+				vidtv_channels_add_registration_s302m(sec);
+				break;
+			default:
+				break;
+			}
+
+			e = e->next;
+		}
+
+		cur_chnl = cur_chnl->next;
+	}
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_channel.h b/drivers/media/test-drivers/vidtv/vidtv_channel.h
new file mode 100644
index 0000000000000..02141c4c732f0
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_channel.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the code for a 'channel' abstraction.
+ *
+ * When vidtv boots, it will create some hardcoded channels.
+ * Their services will be concatenated to populate the SDT.
+ * Their programs will be concatenated to populate the PAT
+ * For each program in the PAT, a PMT section will be created
+ * The PMT section for a channel will be assigned its streams.
+ * Every stream will have its corresponding encoder polled to produce TS packets
+ * These packets may be interleaved by the mux and then delivered to the bridge
+ *
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_CHANNEL_H
+#define VIDTV_CHANNEL_H
+
+#include <linux/types.h>
+#include "vidtv_psi.h"
+#include "vidtv_encoder.h"
+#include "vidtv_mux.h"
+
+struct vidtv_channel {
+	/* a number to identify the TS, chosen at will */
+	u16 transport_stream_id;
+
+	/* will be concatenated into the SDT */
+	struct vidtv_psi_table_sdt_service *service;
+
+	/* the link between SDT, PAT and PMT */
+	u16 program_num;
+
+	/*
+	 * a single program with one or more streams associated with it.
+	 * Will be concatenated into the PAT
+	 */
+	struct vidtv_psi_table_pat_program *program;
+
+	/*
+	 * one or more streams associated with the program
+	 * Will populate the PMT section for this program
+	 */
+	struct vidtv_psi_table_pmt_stream *streams;
+
+	/* a list of encoders, one for each stream */
+	struct vidtv_encoder *encoders;
+
+	struct vidtv_channel *next;
+};
+
+/* init SI data from the channels */
+void vidtv_channel_si_init(struct vidtv_mux *m);
+void vidtv_channel_si_destroy(struct vidtv_mux *m);
+
+void vidtv_channels_init(struct vidtv_mux *m);
+void vidtv_channels_destroy(struct vidtv_mux *m);
+
+void vidtv_channels_add_registration_descs(struct vidtv_mux *m);
+
+#endif //VIDTV_CHANNEL_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
index a0480825b23a9..a13e9331955a7 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_common.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
@@ -13,6 +13,9 @@
 #include <linux/types.h>
 
 #define CLOCK_UNIT_90KHZ 90000
+#define CLOCK_UNIT_27MHZ 27000000
+#define SLEEP_USECS 10000
+#define TRANSPORT_STREAM_ID 0x744
 
 u32 vidtv_memcpy(void *to,
 		 size_t to_offset,
diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.c b/drivers/media/test-drivers/vidtv/vidtv_mux.c
new file mode 100644
index 0000000000000..c9484c491a977
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_mux.c
@@ -0,0 +1,434 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the multiplexer logic for TS packets from different
+ * elementary streams
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+#include <linux/delay.h>
+#include <linux/vmalloc.h>
+#include "vidtv_mux.h"
+#include "vidtv_ts.h"
+#include "vidtv_pes.h"
+#include "vidtv_encoder.h"
+#include "vidtv_channel.h"
+#include "vidtv_common.h"
+#include "vidtv_psi.h"
+
+static struct vidtv_mux_pid_ctx
+*vidtv_mux_get_pid_ctx(struct vidtv_mux *m, u16 pid)
+{
+	struct vidtv_mux_pid_ctx *ctx;
+
+	hash_for_each_possible(m->pid_ctx, ctx, h, pid)
+		if (ctx->pid == pid)
+			return ctx;
+
+	return NULL;
+}
+
+static struct vidtv_mux_pid_ctx
+*vidtv_mux_create_pid_ctx_once(struct vidtv_mux *m, u16 pid)
+{
+	struct vidtv_mux_pid_ctx *ctx;
+
+	ctx = vidtv_mux_get_pid_ctx(m, pid);
+
+	if (ctx)
+		goto end;
+
+	ctx      = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	ctx->pid = pid;
+	ctx->cc  = 0;
+	hash_add(m->pid_ctx, &ctx->h, pid);
+
+end:
+	return ctx;
+}
+
+static void vidtv_mux_pid_ctx_init(struct vidtv_mux *m)
+{
+	struct vidtv_psi_table_pat_program *p = m->si.pat->program;
+
+	hash_init(m->pid_ctx);
+	/* push the pcr pid ctx */
+	vidtv_mux_create_pid_ctx_once(m, m->pcr_pid);
+	/* push the null packet pid ctx */
+	vidtv_mux_create_pid_ctx_once(m, TS_NULL_PACKET_PID);
+	/* push the PAT pid ctx */
+	vidtv_mux_create_pid_ctx_once(m, VIDTV_PAT_PID);
+	/* push the SDT pid ctx */
+	vidtv_mux_create_pid_ctx_once(m, VIDTV_SDT_PID);
+
+	/* add a ctx for all PMT sections */
+	while (p) {
+		vidtv_mux_create_pid_ctx_once(m, p->pid);
+		p = p->next;
+	}
+}
+
+static void vidtv_mux_pid_ctx_destroy(struct vidtv_mux *m)
+{
+	int bkt;
+	struct vidtv_mux_pid_ctx *ctx;
+
+	hash_for_each(m->pid_ctx, bkt, ctx, h) {
+		kfree(ctx);
+	}
+}
+
+static void vidtv_mux_update_clk(struct vidtv_mux *m)
+{
+	/* call this at every thread iteration */
+	u64 elapsed_time;
+
+	/* this will not hold a value yet if we have just started */
+	m->timing.past_jiffies = m->timing.current_jiffies ?
+				 m->timing.current_jiffies :
+				 get_jiffies_64();
+
+	m->timing.current_jiffies = get_jiffies_64();
+
+	elapsed_time = jiffies_to_usecs(m->timing.current_jiffies -
+					m->timing.past_jiffies);
+
+	/* update the 27Mhz clock proportionally to the elapsed time */
+	m->timing.clk += (CLOCK_UNIT_27MHZ / USEC_PER_SEC) * elapsed_time;
+}
+
+static u32 vidtv_mux_push_si(struct vidtv_mux *m)
+{
+	u32 initial_offset = m->ts_buf_offset;
+	struct vidtv_mux_pid_ctx *pat_ctx;
+	struct vidtv_mux_pid_ctx *pmt_ctx;
+	struct vidtv_mux_pid_ctx *sdt_ctx;
+	u32 nbytes; /* the number of bytes written by this function */
+	u16 pmt_pid;
+	u32 i;
+
+	pat_ctx = vidtv_mux_get_pid_ctx(m, VIDTV_PAT_PID);
+	sdt_ctx = vidtv_mux_get_pid_ctx(m, VIDTV_SDT_PID);
+
+	m->ts_buf_offset += vidtv_psi_pat_write_into(m->ts_buf,
+						     m->ts_buf_offset,
+						     m->si.pat,
+						     m->ts_buf_sz,
+						     &pat_ctx->cc);
+
+	for (i = 0; i < m->si.num_pmt_sections; ++i) {
+		pmt_pid = vidtv_psi_pmt_get_pid(&m->si.pmt_secs[i],
+						m->si.pat);
+
+		if (pmt_pid > TS_LAST_VALID_PID) {
+			pr_warn_ratelimited("PID: %d not found\n", pmt_pid);
+			continue;
+		}
+
+		pmt_ctx = vidtv_mux_get_pid_ctx(m, pmt_pid);
+
+		/* write each section into buffer */
+		m->ts_buf_offset += vidtv_psi_pmt_write_into(m->ts_buf,
+							     m->ts_buf_offset,
+							     &m->si.pmt_secs[i],
+							     pmt_pid,
+							     m->ts_buf_sz,
+							     &pmt_ctx->cc);
+	}
+
+	m->ts_buf_offset += vidtv_psi_sdt_write_into(m->ts_buf,
+						     m->ts_buf_offset,
+						     m->si.sdt,
+						     m->ts_buf_sz,
+						     &sdt_ctx->cc);
+
+	nbytes = m->ts_buf_offset - initial_offset;
+	return nbytes;
+}
+
+static u32 vidtv_mux_push_pcr(struct vidtv_mux *m)
+{
+	struct pcr_write_args args = {};
+	struct vidtv_mux_pid_ctx *ctx;
+
+	ctx                     = vidtv_mux_get_pid_ctx(m, m->pcr_pid);
+	args.dest_buf           = m->ts_buf;
+	args.pid                = m->pcr_pid;
+	args.buf_sz             = m->ts_buf_sz;
+	args.continuity_counter = &ctx->cc;
+
+	/* the 27Mhz clock will feed both parts of the PCR bitfield */
+	args.pcr = m->timing.clk;
+
+	return vidtv_ts_pcr_write_into(args);
+}
+
+static bool vidtv_mux_should_push_pcr(struct vidtv_mux *m)
+{
+	u64 next_pcr_at;
+
+	next_pcr_at = m->timing.start_jiffies +
+		      usecs_to_jiffies(m->num_streamed_pcr *
+				       m->timing.pcr_period_usecs);
+
+	return time_after64(m->timing.current_jiffies, next_pcr_at);
+}
+
+static bool vidtv_mux_should_push_si(struct vidtv_mux *m)
+{
+	u64 next_si_at;
+
+	next_si_at = m->timing.start_jiffies +
+		     usecs_to_jiffies(m->num_streamed_si *
+				      m->timing.si_period_usecs);
+
+	return time_after64(m->timing.current_jiffies, next_si_at);
+}
+
+static u32 vidtv_mux_packetize_access_units(struct vidtv_mux *m,
+					    struct vidtv_encoder *e)
+{
+	/* the number of bytes written by this function */
+	u32    nbytes              = 0;
+	struct pes_write_args args = {};
+	u32    initial_offset      = m->ts_buf_offset;
+
+	u32 i;
+	u8 *buf;
+	struct vidtv_mux_pid_ctx *pid_ctx;
+
+	pid_ctx = vidtv_mux_create_pid_ctx_once(m, e->es_pid);
+
+	args.dest_buf           = m->ts_buf;
+	args.dest_buf_sz        = m->ts_buf_sz;
+	args.pid                = e->es_pid;
+	args.is_s302m_pkt       = (e->id == S302M);
+	args.continuity_counter = &pid_ctx->cc;
+	args.send_pts           = true;
+
+	for (i = 0; i < e->nunits; ++i) {
+		buf                  = e->encoder_buf + e->offsets[i];
+		args.from            = buf;
+		args.access_unit_len = e->nbytes[i];
+		args.dest_offset     = m->ts_buf_offset;
+		args.pts             = e->pts[i];
+
+		m->ts_buf_offset += vidtv_pes_write_into(args);
+	}
+
+	/* clear the encoder state once we have written the current ES data */
+	e->clear(e);
+
+	nbytes = m->ts_buf_offset - initial_offset;
+	return nbytes;
+}
+
+static u32 vidtv_mux_poll_encoders(struct vidtv_mux *m)
+{
+	u32    nbytes                  = 0;
+	struct vidtv_channel *cur_chnl = m->channels;
+	struct vidtv_encoder *e        = NULL;
+
+	u64    elapsed_time_usecs = jiffies_to_usecs(m->timing.current_jiffies -
+						     m->timing.past_jiffies);
+	while (cur_chnl) {
+		e = cur_chnl->encoders;
+
+		while (e) {
+			/* encode for 'elapsed_time_usecs' */
+			e->encode(e, elapsed_time_usecs);
+			/* get the TS packets into the mux buffer */
+			nbytes += vidtv_mux_packetize_access_units(m, e);
+			/* grab next encoder */
+			e = e->next;
+		}
+
+		/* grab the next channel */
+		cur_chnl = cur_chnl->next;
+	}
+
+	return nbytes;
+}
+
+static u32 vidtv_mux_pad_with_nulls(struct vidtv_mux *m, u32 npkts)
+{
+	struct null_packet_write_args args = {};
+	u32    initial_offset              = m->ts_buf_offset;
+	u32 nbytes; /* the number of bytes written by this function */
+	u32 i;
+	struct vidtv_mux_pid_ctx *ctx;
+
+	ctx = vidtv_mux_get_pid_ctx(m, TS_NULL_PACKET_PID);
+
+	args.dest_buf           = m->ts_buf;
+	args.buf_sz             = m->ts_buf_sz;
+	args.continuity_counter = &ctx->cc;
+	args.dest_offset        = m->ts_buf_offset;
+
+	for (i = 0; i < npkts; ++i) {
+		m->ts_buf_offset += vidtv_ts_null_write_into(args);
+		args.dest_offset  = m->ts_buf_offset;
+	}
+
+	nbytes = m->ts_buf_offset - initial_offset;
+
+	/* sanity check */
+	if (nbytes != npkts * TS_PACKET_LEN)
+		pr_err_ratelimited("%d != %d\n", nbytes, npkts * TS_PACKET_LEN);
+
+	return nbytes;
+}
+
+static u32 vidtv_mux_check_mux_rate(struct vidtv_mux *m)
+{
+	/*
+	 * attempt to maintain a constant mux rate, padding with null packets
+	 * if needed
+	 */
+
+	u32 nbytes = 0;  /* the number of bytes written by this function */
+
+	u64 nbytes_expected; /* the number of bytes we should have written */
+	u64 nbytes_streamed; /* the number of bytes we actually wrote */
+	u32 num_null_pkts; /* number of null packets to bridge the gap */
+
+	u64 elapsed_time_usecs = jiffies_to_usecs(m->timing.current_jiffies -
+						  m->timing.past_jiffies);
+
+	nbytes_expected  = (m->mux_rate_kbytes_sec / 1000) / USEC_PER_SEC;
+	nbytes_expected *= elapsed_time_usecs;
+
+	nbytes_streamed = m->num_streamed_pkts * TS_PACKET_LEN;
+
+	if (nbytes_streamed < nbytes_expected) {
+		/* can't write half a packet: roundup to a 188 multiple */
+		nbytes_expected  = roundup(nbytes_expected, TS_PACKET_LEN);
+		num_null_pkts    = nbytes_expected / TS_PACKET_LEN;
+		nbytes          += vidtv_mux_pad_with_nulls(m, num_null_pkts);
+	}
+
+	return nbytes;
+}
+
+static void vidtv_mux_clear(struct vidtv_mux *m)
+{
+	/* clear the packets currently in the mux */
+	memset(m->ts_buf, 0, m->ts_buf_sz);
+	/* point to the beginning of the buffer again */
+	m->ts_buf_offset = 0;
+}
+
+static void vidtv_mux_tick(struct work_struct *work)
+{
+	struct vidtv_mux *m = container_of(work,
+					   struct vidtv_mux,
+					   mpeg_thread);
+	u32 nbytes;
+	u32 npkts;
+
+	while (m->streaming) {
+		nbytes = 0;
+
+		vidtv_mux_update_clk(m);
+
+		if (vidtv_mux_should_push_pcr(m))
+			nbytes += vidtv_mux_push_pcr(m);
+
+		if (vidtv_mux_should_push_si(m))
+			nbytes += vidtv_mux_push_si(m);
+
+		nbytes += vidtv_mux_poll_encoders(m);
+
+		nbytes += vidtv_mux_check_mux_rate(m);
+
+		npkts = nbytes / TS_PACKET_LEN;
+
+		/* if the buffer is not aligned there is a bug somewhere */
+		if (nbytes % TS_PACKET_LEN)
+			pr_err_ratelimited("Misaligned buffer\n");
+
+		if (m->on_new_packets_available_cb)
+			m->on_new_packets_available_cb(m->priv,
+						       m->ts_buf,
+						       npkts);
+
+		m->num_streamed_pkts += npkts;
+		vidtv_mux_clear(m);
+
+		usleep_range(SLEEP_USECS, 2 * SLEEP_USECS);
+	}
+}
+
+void vidtv_mux_start_thread(struct vidtv_mux *m)
+{
+	if (m->streaming) {
+		pr_warn_ratelimited("Already streaming. Skipping.\n");
+		return;
+	}
+
+	m->streaming            = true;
+	m->timing.start_jiffies = get_jiffies_64();
+	schedule_work(&m->mpeg_thread);
+}
+
+void vidtv_mux_stop_thread(struct vidtv_mux *m)
+{
+	/* thread will quit */
+	m->streaming = false;
+}
+
+struct vidtv_mux *vidtv_mux_init(struct vidtv_mux_init_args args)
+{
+	struct vidtv_mux *m = kzalloc(sizeof(*m), GFP_KERNEL);
+
+	m->timing.pcr_period_usecs = args.pcr_period_usecs;
+	m->timing.si_period_usecs  = args.si_period_usecs;
+
+	m->mux_rate_kbytes_sec = args.mux_rate_kbytes_sec;
+
+	m->on_new_packets_available_cb = args.on_new_packets_available_cb;
+
+	m->ts_buf    = vzalloc(args.ts_buf_sz);
+	m->ts_buf_sz = args.ts_buf_sz;
+
+	m->si.pat = kzalloc(sizeof(*m->si.pat), GFP_KERNEL);
+	m->si.sdt = kzalloc(sizeof(*m->si.sdt), GFP_KERNEL);
+
+	vidtv_channels_init(m);
+
+	/* will alloc data for pmt_sections after initializing pat */
+	vidtv_channel_si_init(m);
+
+	INIT_WORK(&m->mpeg_thread, vidtv_mux_tick);
+
+	m->pcr_pid = args.pcr_pid;
+	m->priv    = args.priv;
+
+	vidtv_mux_pid_ctx_init(m);
+	vidtv_channels_add_registration_descs(m);
+
+	return m;
+}
+
+void vidtv_mux_destroy(struct vidtv_mux *m)
+{
+	vidtv_mux_pid_ctx_destroy(m);
+	vidtv_channel_si_destroy(m);
+	vidtv_channels_destroy(m);
+	kfree(m->si.sdt);
+	kfree(m->si.pat);
+	kfree(m->ts_buf);
+	kfree(m);
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_mux.h b/drivers/media/test-drivers/vidtv/vidtv_mux.h
new file mode 100644
index 0000000000000..1dffa2010d518
--- /dev/null
+++ b/drivers/media/test-drivers/vidtv/vidtv_mux.h
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Vidtv serves as a reference DVB driver and helps validate the existing APIs
+ * in the media subsystem. It can also aid developers working on userspace
+ * applications.
+ *
+ * This file contains the multiplexer logic for TS packets from different
+ * elementary streams
+ *
+ * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef VIDTV_MUX_H
+#define VIDTV_MUX_H
+
+#include <linux/types.h>
+#include <linux/hashtable.h>
+#include <linux/workqueue.h>
+#include "vidtv_psi.h"
+struct vidtv_mux_timing {
+	u64 start_jiffies;
+	u64 current_jiffies;
+	u64 past_jiffies;
+
+	/* a 27Mhz clock from which we will drive the PCR */
+	u64 clk;
+
+	u64 pcr_period_usecs;
+	u64 si_period_usecs;
+};
+
+struct vidtv_mux_si {
+	/* the SI tables */
+	struct vidtv_psi_table_pat *pat;
+	struct vidtv_psi_table_pmt *pmt_secs; /* the PMT sections */
+	/* as many sections as programs in the PAT */
+	u16 num_pmt_sections;
+	struct vidtv_psi_table_sdt *sdt;
+};
+
+struct vidtv_mux_pid_ctx {
+	u16 pid;
+	u8 cc; /* continuity counter */
+	struct hlist_node h;
+};
+
+struct vidtv_mux {
+	struct vidtv_mux_timing timing;
+
+	/* the bit rate for the TS, in kbytes */
+	u32 mux_rate_kbytes_sec;
+
+	/* a hash table to keep track of per-PID metadata */
+	DECLARE_HASHTABLE(pid_ctx, 3);
+
+	/* a callback to inform of new TS packets ready */
+	void (*on_new_packets_available_cb)(void *priv, u8 *buf, u32 npackets);
+
+	/* the TS buffer */
+	u8 *ts_buf;
+
+	/* the TS buffer size */
+	u32 ts_buf_sz;
+
+	/* where we are in the TS buffer now */
+	u32 ts_buf_offset;
+
+	/* a list of channels */
+	struct vidtv_channel  *channels;
+
+	struct vidtv_mux_si si;
+	u64 num_streamed_pcr;
+	u64 num_streamed_si;
+
+	/* total number of packets streamed */
+	u64 num_streamed_pkts;
+
+	struct work_struct mpeg_thread;
+
+	/* whether to keep running the main loop */
+	bool streaming;
+
+	/* the pcr PID for _all_ channels */
+	u16 pcr_pid;
+
+	void *priv;
+};
+
+struct vidtv_mux_init_args {
+	u32 mux_rate_kbytes_sec;
+	void (*on_new_packets_available_cb)(void *priv, u8 *buf, u32 npackets);
+	u32 ts_buf_sz;
+	u64 pcr_period_usecs;
+	u64 si_period_usecs;
+	u16 pcr_pid;
+	void *priv;
+};
+
+struct vidtv_mux *vidtv_mux_init(struct vidtv_mux_init_args args);
+void vidtv_mux_destroy(struct vidtv_mux *m);
+
+void vidtv_mux_start_thread(struct vidtv_mux *m);
+void vidtv_mux_stop_thread(struct vidtv_mux *m);
+
+#endif //VIDTV_MUX_H
diff --git a/drivers/media/test-drivers/vidtv/vidtv_psi.c b/drivers/media/test-drivers/vidtv/vidtv_psi.c
index 51e9114173362..d9547efe4626b 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_psi.c
+++ b/drivers/media/test-drivers/vidtv/vidtv_psi.c
@@ -1035,3 +1035,21 @@ vidtv_psi_pmt_create_sec_for_each_pat_entry(struct vidtv_psi_table_pat *pat,
 		program = program->next;
 	}
 }
+
+struct vidtv_psi_table_pmt
+*vidtv_psi_find_pmt_sec(struct vidtv_psi_table_pmt pmt_sections[],
+			u16 nsections,
+			u16 program_num)
+{
+	/* find the PMT section associated with 'program_num' */
+	struct vidtv_psi_table_pmt *sec = NULL;
+	u32 i;
+
+	for (i = 0; i < nsections; ++i) {
+		sec = &pmt_sections[i];
+		if (be16_to_cpu(sec->header.id) == program_num)
+			return sec;
+	}
+
+	return NULL;
+}
diff --git a/drivers/media/test-drivers/vidtv/vidtv_psi.h b/drivers/media/test-drivers/vidtv/vidtv_psi.h
index 77b616a46757a..f45540d53b351 100644
--- a/drivers/media/test-drivers/vidtv/vidtv_psi.h
+++ b/drivers/media/test-drivers/vidtv/vidtv_psi.h
@@ -412,4 +412,9 @@ u32 vidtv_psi_pmt_write_into(char *buf,
 			     u32 buf_sz,
 			     u8 *continuity_counter);
 
+struct vidtv_psi_table_pmt
+*vidtv_psi_find_pmt_sec(struct vidtv_psi_table_pmt *pmt_sections,
+			u16 nsections,
+			u16 program_num);
+
 #endif // VIDTV_PSI_H
-- 
2.26.2

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Re: [Linux-kernel-mentees] [RFC, WIP, v6 00/10] media: vidtv: implement a virtual DVB driver

[Shuah Khan]

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> This series is work in progress. It represents the current work done on a
> virtual DVB driver for the Linux media subsystem. I am new to the media
> subsystem and to kernel development in general.
> 
> This driver aims to:
> 	- Serve as template for new DVB driver writers
> 	- Help userspace application writers in general
> 	- Push fake audio/video to userspace for testing
> 		purposes
> 	- Push debug information to userspace via debugfs
> 
> This should currently be able to feed PSI and PCM audio data to
> userspace.
> 
> I appreciate any feedback!
> 

Run checkpatch --strict on these. There are several warns and an error
which could improve the code as well as the improving Kconfig entry
as suggested below.

WARNING: please write a paragraph that describes the config symbol fully
#108: FILE: drivers/media/test-drivers/Kconfig:7:
+menuconfig DVB_TEST_DRIVERS

I will send review comments on individual patches.

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 01/10] media: vidtv: add Kconfig entry

[Shuah Khan]

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> Add the necessary Kconfig entries and a dummy Makefile to compile the new
> virtual DVB test driver (vidtv).
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> ---
>   drivers/media/test-drivers/Kconfig        | 10 ++++++++++
>   drivers/media/test-drivers/Makefile       |  1 +
>   drivers/media/test-drivers/vidtv/Kconfig  | 11 +++++++++++
>   drivers/media/test-drivers/vidtv/Makefile |  2 ++
>   4 files changed, 24 insertions(+)
>   create mode 100644 drivers/media/test-drivers/vidtv/Kconfig
>   create mode 100644 drivers/media/test-drivers/vidtv/Makefile
> 
> diff --git a/drivers/media/test-drivers/Kconfig b/drivers/media/test-drivers/Kconfig
> index 188381c855939..7d273a8a7acc2 100644
> --- a/drivers/media/test-drivers/Kconfig
> +++ b/drivers/media/test-drivers/Kconfig
> @@ -4,6 +4,10 @@ menuconfig V4L_TEST_DRIVERS
>   	bool "V4L test drivers"
>   	depends on VIDEO_DEV
>   
> +menuconfig DVB_TEST_DRIVERS
> +	bool "DVB test drivers"
> +	depends on DVB_CORE && MEDIA_SUPPORT && I2C
> +
>   if V4L_TEST_DRIVERS
>   
>   source "drivers/media/test-drivers/vimc/Kconfig"
> @@ -24,3 +28,9 @@ config VIDEO_VIM2M
>   source "drivers/media/test-drivers/vicodec/Kconfig"
>   
>   endif #V4L_TEST_DRIVERS
> +
> +if DVB_TEST_DRIVERS
> +
> +source "drivers/media/test-drivers/vidtv/Kconfig"
> +
> +endif #DVB_TEST_DRIVERS
> diff --git a/drivers/media/test-drivers/Makefile b/drivers/media/test-drivers/Makefile
> index 74410d3a9f2d2..9f0e4ebb2efe7 100644
> --- a/drivers/media/test-drivers/Makefile
> +++ b/drivers/media/test-drivers/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_VIDEO_VIMC)		+= vimc/
>   obj-$(CONFIG_VIDEO_VIVID)		+= vivid/
>   obj-$(CONFIG_VIDEO_VIM2M)		+= vim2m.o
>   obj-$(CONFIG_VIDEO_VICODEC)		+= vicodec/
> +obj-$(CONFIG_DVB_VIDTV)			+= vidtv/
> diff --git a/drivers/media/test-drivers/vidtv/Kconfig b/drivers/media/test-drivers/vidtv/Kconfig
> new file mode 100644
> index 0000000000000..22c4fd39461f1
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/Kconfig
> @@ -0,0 +1,11 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config DVB_VIDTV
> +	tristate "Virtual DVB Driver (vidtv)"
> +	depends on DVB_CORE && MEDIA_SUPPORT && I2C
> +	help

Add one line summary/name for the driver "Virtual DVB test driver" is
a good description.

> +	  The virtual DVB test driver serves as a reference DVB driver and helps
> +	  validate the existing APIs in the media subsystem. It can also aid developers
> +	  working on userspace applications.
> +

Wrapped lines. Split this to read better.

Take a look at others e.g: drivers/media/test-drivers/vimc/Kconfig
for reference.

> +
> +	  When in doubt, say N.
> diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
> new file mode 100644
> index 0000000000000..d1558d84eeaed
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> 

btw. Did you test it with just this patch?

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 02/10] media: vidtv: implement a tuner driver

[Shuah Khan]

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

Are you using git send-email to send patches. Why do have this
 From line in here? Same comment on all other patches in this series.

> 
> The virtual DVB test driver serves as a reference DVB driver and helps
> validate the existing APIs in the media subsystem. It can also aid developers
> working on userspace applications.
> 
> This dummy tuner should support common TV standards such as DVB-T/T2/S/S2,
> ISDB-T and ATSC when completed.
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> ---
>   drivers/media/test-drivers/vidtv/Makefile     |   3 +
>   .../media/test-drivers/vidtv/vidtv_tuner.c    | 408 ++++++++++++++++++
>   .../media/test-drivers/vidtv/vidtv_tuner.h    |  26 ++
>   3 files changed, 437 insertions(+)
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.h
> 
> diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
> index d1558d84eeaed..58e022c094e5e 100644
> --- a/drivers/media/test-drivers/vidtv/Makefile
> +++ b/drivers/media/test-drivers/vidtv/Makefile
> @@ -1,2 +1,5 @@
>   # SPDX-License-Identifier: GPL-2.0
>   
> +dvb-vidtv-tuner-objs := vidtv_tuner.o
> +
> +obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_tuner.c b/drivers/media/test-drivers/vidtv/vidtv_tuner.c
> new file mode 100644
> index 0000000000000..3f2b4b9a6d568
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_tuner.c
> @@ -0,0 +1,408 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Virtual DVB test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * The vidtv tuner should support common TV standards such as
> + * DVB-T/T2/S/S2, ISDB-T and ATSC when completed.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>

Use Copyright (C) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>

Check other drivers for reference. Do the same in all other files
in this series.

> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
> +
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <media/dvb_frontend.h>
> +#include <linux/printk.h>
> +#include <linux/ratelimit.h>
> +
> +#include "vidtv_tuner.h"
> +
> +MODULE_DESCRIPTION("Virtual DVB Tuner");
> +MODULE_AUTHOR("Daniel W. S. Almeida");
> +MODULE_LICENSE("GPL");
> +
> +struct vidtv_tuner_cnr_to_qual_s {
> +	/* attempt to use the same values as libdvbv5 */
> +	u32 modulation;
> +	u32 fec;
> +	u32 cnr_ok, cnr_good;

Add cnr_good on a separate line.
	u32 cnr_good;
> +};

Add a comment for each of these fields describing
what they are for.

> +
> +static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_c_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QAM_256, FEC_NONE,  34000, 38000},
> +	{ QAM_64,  FEC_NONE,  30000, 34000},
> +};
> +
> +static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_s_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QPSK, FEC_1_2,  7000, 10000},
> +

Any reason for this blank line here?

> +	{ QPSK, FEC_2_3,  9000, 12000},
> +	{ QPSK, FEC_3_4, 10000, 13000},
> +	{ QPSK, FEC_5_6, 11000, 14000},
> +

Any reason for this blank line here?

> +	{ QPSK, FEC_7_8, 12000, 15000},
> +};
> +
> +static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_s2_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QPSK,  FEC_1_2,   9000,  12000},
> +	{ QPSK,  FEC_2_3,  11000,  14000},
> +	{ QPSK,  FEC_3_4,  12000,  15000},
> +	{ QPSK,  FEC_5_6,  12000,  15000},
> +	{ QPSK,  FEC_8_9,  13000,  16000},
> +	{ QPSK,  FEC_9_10, 13500,  16500},
> +	{ PSK_8, FEC_2_3,  14500,  17500},
> +	{ PSK_8, FEC_3_4,  16000,  19000},
> +	{ PSK_8, FEC_5_6,  17500,  20500},
> +	{ PSK_8, FEC_8_9,  19000,  22000},
> +};
> +
> +static const struct vidtv_tuner_cnr_to_qual_s vidtv_tuner_t_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db*/
> +	{   QPSK, FEC_1_2,  4100,  5900},
> +	{   QPSK, FEC_2_3,  6100,  9600},
> +	{   QPSK, FEC_3_4,  7200, 12400},
> +	{   QPSK, FEC_5_6,  8500, 15600},
> +	{   QPSK, FEC_7_8,  9200, 17500},
> +
> +	{ QAM_16, FEC_1_2,  9800, 11800},
> +	{ QAM_16, FEC_2_3, 12100, 15300},
> +	{ QAM_16, FEC_3_4, 13400, 18100},
> +	{ QAM_16, FEC_5_6, 14800, 21300},
> +	{ QAM_16, FEC_7_8, 15700, 23600},
> +
> +	{ QAM_64, FEC_1_2, 14000, 16000},
> +	{ QAM_64, FEC_2_3, 19900, 25400},
> +	{ QAM_64, FEC_3_4, 24900, 27900},
> +	{ QAM_64, FEC_5_6, 21300, 23300},
> +	{ QAM_64, FEC_7_8, 22000, 24000},
> +};
> +
> +struct vidtv_tuner_hardware_state {
> +	bool asleep;
> +	u32 lock_status;
> +	u32 if_frequency;
> +	u32 tuned_frequency;
> +	u32 bandwidth;
> +};
> +

Add a comment for each of these fields describing
what they are for.

> +struct vidtv_tuner_dev {
> +	struct dvb_frontend *fe;
> +	struct vidtv_tuner_hardware_state hw_state;
> +	struct vidtv_tuner_config config;
> +};
> +

Add a comment for each of these fields describing
what they are for.

> +static struct vidtv_tuner_dev*
> +vidtv_tuner_get_dev(struct dvb_frontend *fe)
> +{
> +	struct i2c_client *client = fe->tuner_priv;
> +
> +	return i2c_get_clientdata(client);

Why not simplfy this to just return i2c_get_clientdata(fe->tuner_priv)
Safer to check if tuner_priv is valid.

> +}
> +
> +static s32 vidtv_tuner_check_frequency_shift(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
> +	struct vidtv_tuner_config config  = tuner_dev->config;
> +	u32    *valid_freqs               = NULL;
> +	u32    array_sz                   = 0;
> +	u32 i;
> +	u32 shift;

Align i and shift with the rest of the variables.

> +
> +	switch (c->delivery_system) {

Add indetation for the below:

> +	case SYS_DVBT:
> +	case SYS_DVBT2:
> +		valid_freqs = config.vidtv_valid_dvb_t_freqs;
> +		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_t_freqs);
> +		break;
> +	case SYS_DVBS:
> +	case SYS_DVBS2:
> +		valid_freqs = config.vidtv_valid_dvb_s_freqs;
> +		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_s_freqs);
> +		break;
> +	case SYS_DVBC_ANNEX_A:
> +		valid_freqs = config.vidtv_valid_dvb_c_freqs;
> +		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_c_freqs);
> +		break;
> +
> +	default:
> +		pr_warn("%s: unsupported delivery system: %u\n",
> +			__func__,
> +			c->delivery_system);
> +
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i < array_sz; i++) {
> +		shift = abs(c->frequency - valid_freqs[i]);
> +
> +		if (!shift)
> +			return 0;
> +
> +		/*
> +		 * This will provide a value from 0 to 100 that would
> +		 * indicate how far is the tuned frequency from the
> +		 * right one.
> +		 */
> +		if (shift < config.max_frequency_shift_hz)
> +			return shift * 100 / config.max_frequency_shift_hz;
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int
> +vidtv_tuner_get_signal_strength(struct dvb_frontend *fe, u16 *strength)
> +{
> +	struct dtv_frontend_properties *c          = &fe->dtv_property_cache;

Why do you need white spaces between *c and assignment?

> +	const struct vidtv_tuner_cnr_to_qual_s *cnr2qual = NULL;
> +	u32    array_size                          = 0;

Same here. Don't align them when it doesn't make sense. This makes
it not readable.

> +	s32 shift;
> +	u32 i;
> +
> +	shift = vidtv_tuner_check_frequency_shift(fe);
> +
> +	switch (c->delivery_system) {

Ident.

> +	case SYS_DVBT:
> +	case SYS_DVBT2:
> +		cnr2qual   = vidtv_tuner_t_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_tuner_t_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS:
> +		cnr2qual   = vidtv_tuner_s_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_tuner_s_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS2:
> +		cnr2qual   = vidtv_tuner_s2_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_tuner_s2_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBC_ANNEX_A:
> +		cnr2qual   = vidtv_tuner_c_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_tuner_c_cnr_2_qual);
> +		break;
> +
> +	default:
> +		pr_warn_ratelimited("%s: unsupported delivery system: %u\n",
> +				    __func__,
> +				    c->delivery_system);
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i <= array_size; i++) {
> +		if (cnr2qual[i].modulation != c->modulation ||
> +		    cnr2qual[i].fec != c->fec_inner)
> +			continue;
> +
> +		if (!shift) {
> +			*strength = cnr2qual[i].cnr_good;
> +			return 0;
> +		}
> +		if (shift < 0) {	/* Channel not tuned */
> +			*strength = 0;
> +			return 0;
> +		}
> +		/*
> +		 * Channel tuned at wrong frequency. Simulate that the
> +		 * Carrier S/N ratio is not too good.
> +		 */
> +
> +		*strength = cnr2qual[i].cnr_ok -
> +			    (cnr2qual[i].cnr_good - cnr2qual[i].cnr_ok);
> +		return 0;
> +	}
> +
> +	/*
> +	 * do a linear interpolation between 34dB and 10dB if we can't
> +	 * match against the table
> +	 */
> +	*strength = 34 - 24 * shift / 100;
> +	return 0;
> +}
> +
> +static int vidtv_tuner_init(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +	struct vidtv_tuner_config config  = tuner_dev->config;
> +
> +	msleep_interruptible(config.mock_power_up_delay_msec);
> +
> +	tuner_dev->hw_state.asleep       = false;
> +	tuner_dev->hw_state.if_frequency = 5000;

There is no need to align these.

> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_sleep(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	tuner_dev->hw_state.asleep = true;
> +	return 0;
> +}
> +
> +static int vidtv_tuner_suspend(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	tuner_dev->hw_state.asleep = true;
> +	return 0;
> +}
> +
> +static int vidtv_tuner_resume(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	tuner_dev->hw_state.asleep = false;
> +	return 0;
> +}
> +
> +static int vidtv_tuner_set_params(struct dvb_frontend *fe)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +	struct vidtv_tuner_config config  = tuner_dev->config;
> +	struct dtv_frontend_properties *c = &fe->dtv_property_cache;

Add a blank line and don't try to align these. Looks very odd.

> +	u32    min_freq               = fe->ops.tuner_ops.info.frequency_min_hz;
> +	u32    max_freq               = fe->ops.tuner_ops.info.frequency_max_hz;
> +	u32    min_bw                 = fe->ops.tuner_ops.info.bandwidth_min;
> +	u32    max_bw                 = fe->ops.tuner_ops.info.bandwidth_max;
> +
> +	if (c->frequency < min_freq  || c->frequency > max_freq  ||
> +	    c->bandwidth_hz < min_bw || c->bandwidth_hz > max_bw) {
> +		tuner_dev->hw_state.lock_status = 0;
> +		return -EINVAL;
> +	}
> +
> +	tuner_dev->hw_state.tuned_frequency = c->frequency;
> +	tuner_dev->hw_state.bandwidth       = c->bandwidth_hz;
> +	tuner_dev->hw_state.lock_status     = TUNER_STATUS_LOCKED;
> +
> +	msleep_interruptible(config.mock_tune_delay_msec);
> +	return 0;
> +}
> +
> +static int vidtv_tuner_set_config(struct dvb_frontend *fe,
> +				  void *priv_cfg)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	memcpy(&tuner_dev->config, priv_cfg, sizeof(tuner_dev->config));
> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_get_frequency(struct dvb_frontend *fe,
> +				     u32 *frequency)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	*frequency = tuner_dev->hw_state.tuned_frequency;
> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_get_bandwidth(struct dvb_frontend *fe,
> +				     u32 *bandwidth)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	*bandwidth = tuner_dev->hw_state.bandwidth;
> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_get_if_frequency(struct dvb_frontend *fe,
> +					u32 *frequency)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	*frequency = tuner_dev->hw_state.if_frequency;
> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_get_status(struct dvb_frontend *fe, u32 *status)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = vidtv_tuner_get_dev(fe);
> +
> +	*status = tuner_dev->hw_state.lock_status;
> +
> +	return 0;
> +}
> +
> +static const struct dvb_tuner_ops vidtv_tuner_ops = {
> +	.init             = vidtv_tuner_init,
> +	.sleep            = vidtv_tuner_sleep,
> +	.suspend          = vidtv_tuner_suspend,
> +	.resume           = vidtv_tuner_resume,
> +	.set_params       = vidtv_tuner_set_params,
> +	.set_config       = vidtv_tuner_set_config,
> +	.get_bandwidth    = vidtv_tuner_get_bandwidth,
> +	.get_frequency    = vidtv_tuner_get_frequency,
> +	.get_if_frequency = vidtv_tuner_get_if_frequency,
> +	.get_status       = vidtv_tuner_get_status,
> +	.get_rf_strength  = vidtv_tuner_get_signal_strength
> +};
> +
> +static const struct i2c_device_id vidtv_tuner_i2c_id_table[] = {
> +	{"vidtv_tuner", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, vidtv_tuner_i2c_id_table);
> +
> +static int vidtv_tuner_i2c_probe(struct i2c_client *client,
> +				 const struct i2c_device_id *id)
> +{
> +	struct vidtv_tuner_config *config = client->dev.platform_data;
> +	struct dvb_frontend *fe           = config->fe;
> +	struct vidtv_tuner_dev *tuner_dev = NULL;
> +
> +	tuner_dev = kzalloc(sizeof(*tuner_dev), GFP_KERNEL);
> +	if (!tuner_dev)
> +		return -ENOMEM;
> +
> +	tuner_dev->fe = config->fe;
> +	i2c_set_clientdata(client, tuner_dev);
> +
> +	memcpy(&fe->ops.tuner_ops,
> +	       &vidtv_tuner_ops,
> +	       sizeof(struct dvb_tuner_ops));
> +
> +	fe->tuner_priv = client;
> +
> +	return 0;
> +}
> +
> +static int vidtv_tuner_i2c_remove(struct i2c_client *client)
> +{
> +	struct vidtv_tuner_dev *tuner_dev = i2c_get_clientdata(client);
> +	struct dvb_frontend *fe           = tuner_dev->fe;
> +
> +	memset(&fe->ops.tuner_ops, 0, sizeof(struct dvb_tuner_ops));
> +	fe->tuner_priv = NULL;
> +	kfree(tuner_dev);
> +
> +	return 0;
> +}
> +
> +static struct i2c_driver vidtv_tuner_i2c_driver = {
> +	.driver = {
> +		.name                = "vidtv_tuner",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe    = vidtv_tuner_i2c_probe,
> +	.remove   = vidtv_tuner_i2c_remove,
> +	.id_table = vidtv_tuner_i2c_id_table,
> +};
> +module_i2c_driver(vidtv_tuner_i2c_driver);
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_tuner.h b/drivers/media/test-drivers/vidtv/vidtv_tuner.h
> new file mode 100644
> index 0000000000000..46407739f5d44
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_tuner.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * The Virtual DTV test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + */
> +
> +#ifndef VIDTV_TUNER_H
> +#define VIDTV_TUNER_H
> +
> +#include <linux/types.h>
> +#include <media/dvb_frontend.h>
> +
> +struct vidtv_tuner_config {
> +	struct dvb_frontend *fe;
> +	u32 mock_power_up_delay_msec;
> +	u32 mock_tune_delay_msec;
> +	u32 vidtv_valid_dvb_t_freqs[8];
> +	u32 vidtv_valid_dvb_c_freqs[8];
> +	u32 vidtv_valid_dvb_s_freqs[8];

Don't hrd code these. Add defines for them.

> +	u8  max_frequency_shift_hz;
> +};
> +
> +#endif //VIDTV_TUNER_H
> 

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 03/10] media: vidtv: implement a demodulator driver

[Shuah Khan]

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> Implement a I2C demodulator driver, simulating support for DVB-T, DVB-C
> and DVB-S.
> 
> This demodulator will periodically check the signal quality against a table
> and drop the TS lock if it drops below a threshold value, regaining it in
> the event that the signal improves.
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> ---
>   drivers/media/test-drivers/vidtv/Makefile     |   3 +-
>   .../media/test-drivers/vidtv/vidtv_demod.c    | 444 ++++++++++++++++++
>   .../media/test-drivers/vidtv/vidtv_demod.h    |  41 ++
>   3 files changed, 487 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.h
> 
> diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
> index 58e022c094e5e..21e50c11c94d0 100644
> --- a/drivers/media/test-drivers/vidtv/Makefile
> +++ b/drivers/media/test-drivers/vidtv/Makefile
> @@ -1,5 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   
>   dvb-vidtv-tuner-objs := vidtv_tuner.o
> +dvb-vidtv-demod-objs := vidtv_demod.o
>   
> -obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o
> +obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.c b/drivers/media/test-drivers/vidtv/vidtv_demod.c
> new file mode 100644
> index 0000000000000..15912e063cf5a
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_demod.c
> @@ -0,0 +1,444 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * The Virtual DVB test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + * Based on the example driver written by Emard <emard@softhome.net>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/printk.h>
> +#include <linux/random.h>
> +#include <linux/ratelimit.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/workqueue.h>
> +#include <media/dvb_frontend.h>
> +
> +#include "vidtv_demod.h"
> +
> +// FIXME: just added a random value here
> +#define POLL_THRD_TIME 10 /* ms */
> +
> +static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_c_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QAM_256, FEC_NONE,  34000, 38000},
> +	{ QAM_64,  FEC_NONE,  30000, 34000},
> +};
> +
> +static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_s_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QPSK, FEC_1_2,  7000, 10000},
> +	{ QPSK, FEC_2_3,  9000, 12000},
> +	{ QPSK, FEC_3_4, 10000, 13000},
> +	{ QPSK, FEC_5_6, 11000, 14000},
> +	{ QPSK, FEC_7_8, 12000, 15000},
> +};
> +
> +static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_s2_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db */
> +	{ QPSK,  FEC_1_2,   9000,  12000},
> +	{ QPSK,  FEC_2_3,  11000,  14000},
> +	{ QPSK,  FEC_3_4,  12000,  15000},
> +	{ QPSK,  FEC_5_6,  12000,  15000},
> +	{ QPSK,  FEC_8_9,  13000,  16000},
> +	{ QPSK,  FEC_9_10, 13500,  16500},
> +	{ PSK_8, FEC_2_3,  14500,  17500},
> +	{ PSK_8, FEC_3_4,  16000,  19000},
> +	{ PSK_8, FEC_5_6,  17500,  20500},
> +	{ PSK_8, FEC_8_9,  19000,  22000},
> +};
> +
> +static const struct vidtv_demod_cnr_to_qual_s vidtv_demod_t_cnr_2_qual[] = {
> +	/* from libdvbv5 source code, in milli db*/
> +	{   QPSK, FEC_1_2,  4100,  5900},
> +	{   QPSK, FEC_2_3,  6100,  9600},
> +	{   QPSK, FEC_3_4,  7200, 12400},
> +	{   QPSK, FEC_5_6,  8500, 15600},
> +	{   QPSK, FEC_7_8,  9200, 17500},
> +
> +	{ QAM_16, FEC_1_2,  9800, 11800},
> +	{ QAM_16, FEC_2_3, 12100, 15300},
> +	{ QAM_16, FEC_3_4, 13400, 18100},
> +	{ QAM_16, FEC_5_6, 14800, 21300},
> +	{ QAM_16, FEC_7_8, 15700, 23600},
> +
> +	{ QAM_64, FEC_1_2, 14000, 16000},
> +	{ QAM_64, FEC_2_3, 19900, 25400},
> +	{ QAM_64, FEC_3_4, 24900, 27900},
> +	{ QAM_64, FEC_5_6, 21300, 23300},
> +	{ QAM_64, FEC_7_8, 22000, 24000},
> +};
> +
> +static const struct vidtv_demod_cnr_to_qual_s
> +*vidtv_match_cnr_s(struct dvb_frontend *fe)

Looks very odd:

Move vidtv_match_cnr_s up and:
static const struct vidtv_demod_cnr_to_qual_s
		vidtv_match_cnr_s(struct dvb_frontend *fe)

is better.
			

> +{
> +	struct dtv_frontend_properties *c;
> +	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
> +	u32    array_size                          = 0;

This looks really odd. Don't align them. Align them if it makes
sense. It doesn't here.

> +	u32 i;
> +
> +	c = &fe->dtv_property_cache;
> +
> +	switch (c->delivery_system) {

Indentation

> +	case SYS_DVBT:
> +	case SYS_DVBT2:
> +		cnr2qual   = vidtv_demod_t_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_demod_t_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS:
> +		cnr2qual   = vidtv_demod_s_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_demod_s_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS2:
> +		cnr2qual   = vidtv_demod_s2_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_demod_s2_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBC_ANNEX_A:
> +		cnr2qual   = vidtv_demod_c_cnr_2_qual;
> +		array_size = ARRAY_SIZE(vidtv_demod_c_cnr_2_qual);
> +		break;
> +
> +	default:
> +		pr_warn_ratelimited("%s: unsupported delivery system: %u\n",
> +				    __func__,
> +				    c->delivery_system);
> +		break;
> +	}
> +
> +	for (i = 0; i <= array_size; i++)
> +		if (cnr2qual[i].modulation == c->modulation &&
> +		    cnr2qual[i].fec == c->fec_inner)
> +			return &cnr2qual[i];
> +
> +	return NULL; /* not found */
> +}
> +
> +static void vidtv_demod_poll_snr_handler(struct work_struct *work)
> +{
> +	/*
> +	 * periodically check the signal quality and eventually
> +	 * lose the TS lock if it dips too low
> +	 */
> +	struct vidtv_demod_state *state;
> +	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
> +	struct vidtv_demod_config *config;
> +	u16 snr = 0;
> +
> +	state  = container_of(work, struct vidtv_demod_state, poll_snr.work);
> +	config = &state->config;
> +
> +	if (!state->frontend.ops.tuner_ops.get_rf_strength)
> +		return;
> +
> +	state->frontend.ops.tuner_ops.get_rf_strength(&state->frontend, &snr);
> +
> +	cnr2qual = vidtv_match_cnr_s(&state->frontend);
> +	if (!cnr2qual)
> +		return;
> +
> +	if (snr < cnr2qual->cnr_ok) {
> +		/* eventually lose the TS lock */
> +		if (prandom_u32_max(100) < config->drop_tslock_prob_on_low_snr)
> +			state->status = 0;
> +	} else {
> +		/* recover if the signal improves */
> +		if (prandom_u32_max(100) <
> +		    config->recover_tslock_prob_on_good_snr)
> +			state->status = FE_HAS_SIGNAL  |
> +					FE_HAS_CARRIER |
> +					FE_HAS_VITERBI |
> +					FE_HAS_SYNC    |
> +					FE_HAS_LOCK;
> +	}
> +
> +	schedule_delayed_work(&state->poll_snr,
> +			      msecs_to_jiffies(POLL_THRD_TIME));
> +}
> +
> +static int vidtv_demod_read_status(struct dvb_frontend *fe,
> +				   enum fe_status *status)
> +{
> +	struct vidtv_demod_state *state = fe->demodulator_priv;
> +
> +	*status = state->status;
> +
> +	return 0;
> +}
> +
> +static int vidtv_demod_read_ber(struct dvb_frontend *fe, u32 *ber)
> +{
> +	*ber = 0;
> +	return 0;
> +}
> +
> +static int vidtv_demod_read_signal_strength(struct dvb_frontend *fe,
> +					    u16 *strength)
> +{
> +	*strength = 0;
> +	return 0;
> +}
> +
> +static int vidtv_demod_read_snr(struct dvb_frontend *fe, u16 *snr)
> +{
> +	*snr = 0;
> +	return 0;
> +}
> +
> +static int vidtv_demod_read_ucblocks(struct dvb_frontend *fe, u32 *ucblocks)
> +{
> +	*ucblocks = 0;
> +	return 0;
> +}
> +
> +/*
> + * NOTE:
> + * This is implemented here just to be used as an example for real
> + * demod drivers.
> + *
> + * Should only be implemented if it actually reads something from the hardware.
> + * Also, it should check for the locks, in order to avoid report wrong data
> + * to userspace.
> + */
> +static int vidtv_demod_get_frontend(struct dvb_frontend *fe,
> +				    struct dtv_frontend_properties *p)
> +{
> +	return 0;
> +}
> +
> +static int vidtv_demod_set_frontend(struct dvb_frontend *fe)
> +{
> +	struct vidtv_demod_state *state            = fe->demodulator_priv;
> +	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
> +	u32    tuner_status                        = 0;
> +
> +	if (fe->ops.tuner_ops.set_params) {
> +		fe->ops.tuner_ops.set_params(fe);
> +
> +		/* store the CNR returned by the tuner */
> +		fe->ops.tuner_ops.get_rf_strength(fe, &state->tuner_cnr);
> +
> +		fe->ops.tuner_ops.get_status(fe, &tuner_status);
> +		state->status = (state->tuner_cnr > 0) ?  FE_HAS_SIGNAL  |
> +							  FE_HAS_CARRIER |
> +							  FE_HAS_VITERBI |
> +							  FE_HAS_SYNC    |
> +							  FE_HAS_LOCK	 :
> +							  0;
> +		cnr2qual = vidtv_match_cnr_s(fe);
> +
> +		/* signal isn't good: might lose the lock eventually */
> +		if (tuner_status == TUNER_STATUS_LOCKED &&
> +		    state->tuner_cnr < cnr2qual->cnr_good) {
> +			schedule_delayed_work(&state->poll_snr,
> +					      msecs_to_jiffies(POLL_THRD_TIME));
> +
> +			state->poll_snr_thread_running = true;
> +		}
> +
> +		if (fe->ops.i2c_gate_ctrl)
> +			fe->ops.i2c_gate_ctrl(fe, 0);
> +	}
> +
> +	return 0;
> +}
> +
> +static int vidtv_demod_sleep(struct dvb_frontend *fe)
> +{
> +	struct vidtv_demod_state *state = fe->demodulator_priv;
> +
> +	if (state->poll_snr_thread_running) {
> +		cancel_delayed_work_sync(&state->poll_snr);
> +		state->poll_snr_thread_running = false;
> +		state->poll_snr_thread_restart = true;
> +	}
> +	return 0;
> +}
> +
> +static int vidtv_demod_init(struct dvb_frontend *fe)
> +{
> +	struct vidtv_demod_state *state = fe->demodulator_priv;
> +	u32    tuner_status             = 0;
> +
> +	if (state->cold_start)
> +		INIT_DELAYED_WORK(&state->poll_snr,
> +				  &vidtv_demod_poll_snr_handler);
> +
> +	/*
> +	 * At resume, start the snr poll thread only if it was suspended with
> +	 * the thread running. Extra care should be taken here, as some tuner
> +	 * status change might happen at resume time (for example, due to an
> +	 * ioctl syscall to set_frontend, or due to a release syscall).
> +	 */
> +	fe->ops.tuner_ops.get_status(fe, &tuner_status);
> +
> +	if (tuner_status == TUNER_STATUS_LOCKED &&
> +	    state->poll_snr_thread_restart) {
> +		schedule_delayed_work(&state->poll_snr,
> +				      msecs_to_jiffies(POLL_THRD_TIME));
> +
> +		state->poll_snr_thread_restart = false;
> +	}
> +
> +	state->cold_start = false;
> +	return 0;
> +}
> +
> +/*
> + * NOTE:
> + * This is implemented here just to be used as an example for real
> + * demod drivers.
> + *
> + * Should only be implemented if the demod has support for DVB-S or DVB-S2
> + */
> +static int vidtv_demod_set_tone(struct dvb_frontend *fe,
> +				enum fe_sec_tone_mode tone)
> +{
> +	return 0;
> +}
> +
> +/*
> + * NOTE:
> + * This is implemented here just to be used as an example for real
> + * demod drivers.
> + *
> + * Should only be implemented if the demod has support for DVB-S or DVB-S2
> + */
> +static int vidtv_demod_set_voltage(struct dvb_frontend *fe,
> +				   enum fe_sec_voltage voltage)
> +{
> +	return 0;
> +}
> +
> +static void vidtv_demod_release(struct dvb_frontend *fe)
> +{
> +	struct vidtv_demod_state *state = fe->demodulator_priv;
> +
> +	if (state->poll_snr_thread_running)
> +		cancel_delayed_work_sync(&state->poll_snr);
> +
> +	kfree(state);
> +}
> +
> +static const struct dvb_frontend_ops vidtv_demod_ops = {
> +	.delsys = {
> +		SYS_DVBT,
> +		SYS_DVBT2,
> +		SYS_DVBC_ANNEX_A,
> +		SYS_DVBS,
> +		SYS_DVBS2,
> +	},
> +
> +	.info = {
> +		.name                   = "Dummy demod for DVB-T/T2/C/S/S2",
> +		.frequency_min_hz       = 51 * MHz,
> +		.frequency_max_hz       = 2150 * MHz,
> +		.frequency_stepsize_hz  = 62500,
> +		.frequency_tolerance_hz = 29500 * kHz,
> +		.symbol_rate_min        = 1000000,
> +		.symbol_rate_max        = 45000000,
> +
> +		.caps = FE_CAN_FEC_1_2 |
> +			FE_CAN_FEC_2_3 |
> +			FE_CAN_FEC_3_4 |
> +			FE_CAN_FEC_4_5 |
> +			FE_CAN_FEC_5_6 |
> +			FE_CAN_FEC_6_7 |
> +			FE_CAN_FEC_7_8 |
> +			FE_CAN_FEC_8_9 |
> +			FE_CAN_FEC_AUTO |

Here is the first one.

> +			FE_CAN_QAM_16 |
> +			FE_CAN_QAM_64 |
> +			FE_CAN_QAM_32 |
> +			FE_CAN_QAM_128 |
> +			FE_CAN_QAM_256 |
> +			FE_CAN_QAM_AUTO |
> +			FE_CAN_QPSK |
> +			FE_CAN_FEC_AUTO |

Duplicate entry? Cut and paste error perhaps.

> +			FE_CAN_INVERSION_AUTO |
> +			FE_CAN_TRANSMISSION_MODE_AUTO |
> +			FE_CAN_GUARD_INTERVAL_AUTO |
> +			FE_CAN_HIERARCHY_AUTO,
> +	},
> +
> +	.release = vidtv_demod_release,
> +
> +	.init  = vidtv_demod_init,
> +	.sleep = vidtv_demod_sleep,
> +
> +	.set_frontend = vidtv_demod_set_frontend,
> +	.get_frontend = vidtv_demod_get_frontend,
> +
> +	.read_status          = vidtv_demod_read_status,
> +	.read_ber             = vidtv_demod_read_ber,
> +	.read_signal_strength = vidtv_demod_read_signal_strength,
> +	.read_snr             = vidtv_demod_read_snr,
> +	.read_ucblocks        = vidtv_demod_read_ucblocks,
> +
> +	/* For DVB-S/S2 */
> +	.set_voltage = vidtv_demod_set_voltage,
> +	.set_tone    = vidtv_demod_set_tone,
> +};
> +
> +static const struct i2c_device_id vidtv_demod_i2c_id_table[] = {
> +	{"vidtv_demod", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, vidtv_demod_i2c_id_table);
> +
> +static int vidtv_demod_i2c_probe(struct i2c_client *client,
> +				 const struct i2c_device_id *id)
> +{
> +	struct vidtv_demod_state *state;
> +
> +	/* allocate memory for the internal state */
> +	state = kzalloc(sizeof(*state), GFP_KERNEL);
> +	if (!state)
> +		return -ENOMEM;
> +
> +	/* create dvb_frontend */
> +	memcpy(&state->frontend.ops,
> +	       &vidtv_demod_ops,
> +	       sizeof(struct dvb_frontend_ops));
> +
> +	state->frontend.demodulator_priv = state;
> +	i2c_set_clientdata(client, state);
> +
> +	return 0;
> +}
> +
> +static int vidtv_demod_i2c_remove(struct i2c_client *client)
> +{
> +	struct vidtv_demod_state *state = i2c_get_clientdata(client);
> +
> +	memset(&state->frontend.ops, 0, sizeof(struct dvb_frontend_ops));
> +	state->frontend.demodulator_priv = NULL;
> +	kfree(state);
> +
> +	return 0;
> +}
> +
> +static struct i2c_driver vidtv_demod_i2c_driver = {
> +	.driver = {
> +		.name                = "vidtv_demod",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe    = vidtv_demod_i2c_probe,
> +	.remove   = vidtv_demod_i2c_remove,
> +	.id_table = vidtv_demod_i2c_id_table,
> +};
> +
> +module_i2c_driver(vidtv_demod_i2c_driver);
> +
> +MODULE_DESCRIPTION("Virtual DVB Demodulator Driver");
> +MODULE_AUTHOR("Daniel W. S. Almeida");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_demod.h b/drivers/media/test-drivers/vidtv/vidtv_demod.h
> new file mode 100644
> index 0000000000000..b14957d9d4ea0
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_demod.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * The Virtual DTV test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>

Change it to Copyright. Same comment on all files in this series.

> + * Based on the example driver written by Emard <emard@softhome.net>
> + */
> +
> +#ifndef VIDTV_DEMOD_H
> +#define VIDTV_DEMOD_H
> +
> +#include <linux/dvb/frontend.h>
> +#include <media/dvb_frontend.h>
> +
> +struct vidtv_demod_cnr_to_qual_s {
> +	/* attempt to use the same values as libdvbv5 */
> +	u32 modulation;
> +	u32 fec;
> +	u32 cnr_ok, cnr_good;

Move cnr_good to a separate line. Describe these variables.
Whatare they for and what they do.

> +};
> +
> +struct vidtv_demod_config {
> +	/* probability of losing the lock due to low snr */
> +	u8 drop_tslock_prob_on_low_snr;
> +	/* probability of recovering when the signal improves */
> +	u8 recover_tslock_prob_on_good_snr;
> +};
> +
> +struct vidtv_demod_state {
> +	struct dvb_frontend frontend;
> +	struct vidtv_demod_config config;
> +	struct delayed_work poll_snr;
> +	enum fe_status status;
> +	u16 tuner_cnr;
> +	bool cold_start;
> +	bool poll_snr_thread_running;
> +	bool poll_snr_thread_restart;
> +};
> +#endif // VIDTV_DEMOD_H
> 

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 00/10] media: vidtv: implement a virtual DVB driver

[Shuah Khan]

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> This series is work in progress. It represents the current work done on a
> virtual DVB driver for the Linux media subsystem. I am new to the media
> subsystem and to kernel development in general.
> 
> This driver aims to:
> 	- Serve as template for new DVB driver writers
> 	- Help userspace application writers in general
> 	- Push fake audio/video to userspace for testing
> 		purposes
> 	- Push debug information to userspace via debugfs
> 
> This should currently be able to feed PSI and PCM audio data to
> userspace.
> 
> I appreciate any feedback!
> 
> Changes in v6:
> 	Addressed the following issues:
> 	- Makefile was not actually compiling everything;
> 	- The bridge driver should be a platform driver;
> 	- There are lots of warnings and other errors produced
> 	by the driver.
> 
> Changes in v5:
> 
> Removed all calls to WARN_ON in favor of pr_warn_ratelimited
> Add a #define for pr_fmt
> Reworked the byte swapping logic for big/little endian support:
> 	big endian fields now prepended with __beXX for 'sparse' checks
> 	bitfields now laid in reverse order if LITTLE_ENDIAN_BITFIELD
> 		is set
> 
> media: vidtv: implement a tuner driver
> 	Return -EINVAL instead of -1 in vidtv_tuner_check_frequency_shift
> media: vidtv: implement a demodulator driver
> 	Add POLL_THRD_TIME #define
> 	Implement dvb_frontend_ops as a single struct instead of three
> media: vidtv: move config structs into a separate header
> 	Removed this commit, configs are now in vidtv_tuner.h and vidtv_demod.h
> media: vidtv: add a bridge driver
> 	module_param: all fs permissions set to 0
> 	removed param 'chosen_delsys'
> 	module_param: removed "optional" string: all module_params are optional
> 	renamed vidtv_bridge -> vidtv_bridg: so the source code and module names
> 		are different
> media: vidtv: add wrappers for memcpy and memset
> 	Added kernel-docs
> 	write address is now computed internally
> media: vidtv: add MPEG TS common code
> 	Drop packets if the buffer is full
> media: vidtv: implement a PSI generator
> 	Removed vidtv_psi_ts_psi_write_stuffing()
> 	Forcibly align misaligned buffers
> 	Drop packets if buffer is full
> media: vidtv: implement a PES packetizer
> 	Remove vidtv_extract_bits() in favor of GENMASK() and bitwise &
> 	Forcibly align misaligned buffers
> media: vidtv: Implement a SMPTE 302M encoder
> 	Added kernel-docs for struct vidtv_encoder
> media: vidtv: Add a MPEG Transport Stream Multiplexer
> 	Added check for minimum and maximum buffer size.
> 	Drop packets if buffer is full
> 
> 
> Changes in v4:
> Added a PES packetizer
> Implemented a minimum version of the SMPTE 302m encoder for AES3 audio
> Fixed endianness in the PSI generator, converting fields to big endian where applicable
> Added a minimal TS mux abstraction
> 
> Changes in v3:
> Added a bridge driver
> Renamed the driver to vidtv
> Renamed/reworked commits into smaller pieces
> Moved the driver into its own directory
> Fixed the code for the signal strength in the tuner
> Removed useless enums in the tuner driver (e.g. lock_status, power_status...)
> Reworked the logic for the poll_snr thread in the demodulator driver
> Moved MPEG related code to the bridge driver, as it controls the demux logic
> Changed literals to #defines, used sizeof in place of integer literals when
> computing the size of PSI structs
> Moved the MPEG PSI tables to the heap to reduce stack space usage
> Now using usleep_range in place of msleep_interruptible in the MPEG TS thread
> Wrapped memcpy and memset to protect against buffer overflow when writing to the
> MPEG TS buffer.
> 
> Changes in v2:
> Attempted not to break assignments into multiple lines as much as possible.
> Code now passes checkpatch strict mode
> 
> media: dvb_dummy_tuner: implement driver skeleton	
> Changed snr values to mili db
> Return value from 0-100 to indicate how far off the requested
> frequency is from a valid one
> 
> Use the frequency shift to interpolate between 34dB and 10dB if
> we can not match against the SNR lookup table
> Remove sleep calls for suspend/resume
> 
> Fix memcpy call for the config struct
> 
> media: dvb_dummy_fe.c: lose TS lock on bad snr
> Randomly recover the TS lock if the signal quality improves
> 
> media: dvb_dummy_fe.c: write PSI information into DMX buffer
> Split the patch into multiple header/source files
> 
> Hexadecimal literals are now lower case
> 
> Prefer short function names / reduce function signatures
> 
> Add #defines for constants when computing section lengths
> 
> Change signature for functions that take a dummy channel as
> argument (i.e. channels* is now channels[NUM_CHANNELS])
> 
> Daniel W. S. Almeida (10):
>    media: vidtv: add Kconfig entry
>    media: vidtv: implement a tuner driver

You can collapse patch 1 and 2. I don't see why you need two
separate patches.

>    media: vidtv: implement a demodulator driver
>    media: vidtv: add a bridge driver
>    media: vidtv: add wrappers for memcpy and memset
>    media: vidtv: add MPEG TS common code
>    media: vidtv: implement a PSI generator
>    media: vidtv: implement a PES packetizer
>    media: vidtv: Implement a SMPTE 302M encoder
>    media: vidtv: Add a MPEG Transport Stream Multiplexer
> 
>   arch/Kconfig                                  |    2 +-

Why do you need this change. It is part of patch 04 with no
explanation on why this change is necessary.


>   drivers/media/dvb-core/dvbdev.c               |    1 +

Same here.

>   drivers/media/test-drivers/Kconfig            |   10 +
>   drivers/media/test-drivers/Makefile           |    1 +
>   drivers/media/test-drivers/vidtv/Kconfig      |   11 +
>   drivers/media/test-drivers/vidtv/Makefile     |    9 +
>   .../media/test-drivers/vidtv/vidtv_bridge.c   |  511 ++++++++
>   .../media/test-drivers/vidtv/vidtv_bridge.h   |   41 +
>   .../media/test-drivers/vidtv/vidtv_channel.c  |  339 ++++++
>   .../media/test-drivers/vidtv/vidtv_channel.h  |   66 ++
>   .../media/test-drivers/vidtv/vidtv_common.c   |   86 ++
>   .../media/test-drivers/vidtv/vidtv_common.h   |   34 +
>   .../media/test-drivers/vidtv/vidtv_demod.c    |  444 +++++++
>   .../media/test-drivers/vidtv/vidtv_demod.h    |   41 +
>   .../media/test-drivers/vidtv/vidtv_encoder.h  |  103 ++
>   drivers/media/test-drivers/vidtv/vidtv_mux.c  |  434 +++++++
>   drivers/media/test-drivers/vidtv/vidtv_mux.h  |  105 ++
>   drivers/media/test-drivers/vidtv/vidtv_pes.c  |  450 +++++++
>   drivers/media/test-drivers/vidtv/vidtv_pes.h  |  186 +++
>   drivers/media/test-drivers/vidtv/vidtv_psi.c  | 1055 +++++++++++++++++
>   drivers/media/test-drivers/vidtv/vidtv_psi.h  |  420 +++++++
>   .../media/test-drivers/vidtv/vidtv_s302m.c    |  636 ++++++++++
>   .../media/test-drivers/vidtv/vidtv_s302m.h    |  119 ++
>   drivers/media/test-drivers/vidtv/vidtv_ts.c   |  157 +++
>   drivers/media/test-drivers/vidtv/vidtv_ts.h   |  120 ++
>   .../media/test-drivers/vidtv/vidtv_tuner.c    |  408 +++++++
>   .../media/test-drivers/vidtv/vidtv_tuner.h    |   26 +
>   27 files changed, 5814 insertions(+), 1 deletion(-)
>   create mode 100644 drivers/media/test-drivers/vidtv/Kconfig
>   create mode 100644 drivers/media/test-drivers/vidtv/Makefile
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_channel.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_demod.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_encoder.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_mux.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_pes.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_psi.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_s302m.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_ts.h
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_tuner.h
> 

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 05/10] media: vidtv: add wrappers for memcpy and memset

[Shuah Khan]

Hi Daniel,

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> A lot of code in this driver is for serializing structures. This is
> error prone.
> 
> Therefore, prevent buffer overflows by wrapping memcpy and memset,
> comparing the requested length against the buffer size.
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> ---
>   .../media/test-drivers/vidtv/vidtv_common.c   | 86 +++++++++++++++++++
>   .../media/test-drivers/vidtv/vidtv_common.h   | 27 ++++++
>   2 files changed, 113 insertions(+)
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_common.h
> 

I don't see these added to Makefile. Building the driver with the patch
has no effect.

In any case I don't see any value in adding the wrappers here. They
really do nothing other than doing range checks. It adda a layer of
indirection that is unnecessary.

> diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.c b/drivers/media/test-drivers/vidtv/vidtv_common.c
> new file mode 100644
> index 0000000000000..6810212087c17
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_common.c
> @@ -0,0 +1,86 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Virtual DVB test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
> +
> +#include <linux/printk.h>
> +#include <linux/ratelimit.h>
> +#include <linux/string.h>
> +#include <linux/types.h>
> +
> +#include "vidtv_common.h"
> +
> +/**
> + * vidtv_memcpy() - wrapper routine to be used by MPEG-TS
> + *	generator, in order to avoid going past the
> + *	output buffer.
> + * @to:	Starting element to where a MPEG-TS packet will
> + *	be copied.
> + * @to_offset:	Starting position of the @to buffer to be filled.
> + * @to_size:	Size of the @to buffer.
> + * @from:	Starting element of the buffer to be copied.
> + * @len:	Number of elements to be copy from @from buffer
> + *	into @to+ @to_offset buffer.
> + *
> + * Note:
> + *	Real digital TV demod drivers should not have memcpy
> + *	wrappers. We use it here because emulating MPEG-TS
> + *	generation at kernelspace requires some extra care.
> + *
> + * Return:
> + *	Returns the number of bytes written
> + */
> +u32 vidtv_memcpy(void *to,
> +		 size_t to_offset,
> +		 size_t to_size,
> +		 const void *from,
> +		 size_t len)
> +{
> +	if (unlikely(to_offset + len > to_size)) {

Use of unlikely isn't necessarily beneficial in all cases.

> +		pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size\n");
> +		return 0;
> +	}
> +
> +	memcpy(to + to_offset, from, len);
> +	return len;
> +}
> +
> +/**
> + * vidtv_memset() - wrapper routine to be used by MPEG-TS
> + *	generator, in order to avoid going past the
> + *	output buffer.
> + * @to:	Starting element to set
> + * @to_offset:	Starting position of the @to buffer to be filled.
> + * @to_size:	Size of the @to buffer.
> + * @from:	Starting element of the buffer to be copied.
> + * @ten:	Number of elements to be copy from @from buffer
> + *	into @to+ @to_offset buffer.
> + *
> + * Note:
> + *	Real digital TV demod drivers should not have memset
> + *	wrappers. We use it here because emulating MPEG-TS
> + *	generation at kernelspace requires some extra care.
> + *
> + * Return:
> + *	Returns the number of bytes written
> + */
> +u32 vidtv_memset(void *to,
> +		 size_t to_offset,
> +		 size_t to_size,
> +		 const int c,
> +		 size_t len)
> +{
> +	if (unlikely(to_offset + len > to_size)) {
> +		pr_err_ratelimited("overflow detected, skipping. Try increasing the buffer size\n");
> +		return 0;
> +	}
> +
> +	memset(to + to_offset, c, len);
> +	return len;
> +}
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_common.h b/drivers/media/test-drivers/vidtv/vidtv_common.h
> new file mode 100644
> index 0000000000000..a3cb303cc7423
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_common.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * The Virtual DVB test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + */
> +
> +#ifndef VIDTV_COMMON_H
> +#define VIDTV_COMMON_H
> +
> +#include <linux/types.h>
> +
> +u32 vidtv_memcpy(void *to,
> +		 size_t to_offset,
> +		 size_t to_size,
> +		 const void *from,
> +		 size_t len);
> +
> +u32 vidtv_memset(void *to,
> +		 size_t to_offset,
> +		 size_t to_size,
> +		 int c,
> +		 size_t len);
> +
> +#endif // VIDTV_COMMON_H
> 

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 04/10] media: vidtv: add a bridge driver

[Shuah Khan]

Hi Daniel,

On 5/20/20 1:03 AM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> Digital TV devices consist of several independent hardware components which
> are controlled by different drivers.
> Each media device is controlled by a group of cooperating drivers with the
> bridge driver as the main driver.
> 
> This patch adds a bridge driver for the Virtual Digital TV driver [vidtv].
> 
> The bridge driver binds to the other drivers, that is, vidtv_tuner and
> vidtv_demod and implements the digital demux logic, providing userspace
> with a MPEG Transport Stream.
> 
> Move config structs to a common header so they can be used by the bridge
> driver and by their respective drivers.
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> 
> BRIDGE WIP
> ---
>   arch/Kconfig                                  |   2 +-
>   drivers/media/dvb-core/dvbdev.c               |   1 +
>   drivers/media/test-drivers/vidtv/Makefile     |   4 +-
>   .../media/test-drivers/vidtv/vidtv_bridge.c   | 435 ++++++++++++++++++
>   .../media/test-drivers/vidtv/vidtv_bridge.h   |  39 ++
>   5 files changed, 479 insertions(+), 2 deletions(-)
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.c
>   create mode 100644 drivers/media/test-drivers/vidtv/vidtv_bridge.h
> 

I ran a test and does't look like you are releasing demod and tuner
module when removing dvb_vidtv_bridge. Probe for these happens when

After modprobe dvb_vidtv_bridge and lsmod shows all 3 modules.
dvb_vidtv_demod        16384  0
dvb_vidtv_bridge       45056  0
dvb_core              143360  1 dvb_vidtv_bridge

After rmmod dvb_vidtv_bridge, lsmod shows

dvb_vidtv_tuner        16384  0
dvb_vidtv_demod        16384  0

vidtv_bridge_remove() doesn't seem to cleaning up completely and
releasing thes modules vidtv_bridge_init() loads. Also it has to
delete i2c adapter that is added in vidtv_bridge_init(). Call
to i2c_del_adapter() is miising in vidtv_bridge_remove()

Please see commnets inline after vidtv_bridge_remove().

After a couple of modprobe and rmmods on dvb_vidtv_bridge, I see
paninc after modprobe.

[ 3651.863602] dvbdev: DVB: registering new adapter (dvb_vidtv_bridge)
[ 3821.179081] dvbdev: DVB: registering new adapter (dvb_vidtv_bridge)
[ 4087.198087] dvbdev: DVB: registering new adapter (dvb_vidtv_bridge)
[ 4087.202732] i2c i2c-10: DVB: registering adapter 0 frontend 0 (Dummy 
demod for DVB-T/T2/C/S/S2)...
[ 4087.203112] BUG: kernel NULL pointer dereference, address: 
0000000000000000
[ 4087.203140] #PF: supervisor read access in kernel mode
[ 4087.203142] #PF: error_code(0x0000) - not-present page
[ 4087.203144] PGD 0 P4D 0
[ 4087.203147] Oops: 0000 [#1] SMP NOPTI
[ 4087.203150] CPU: 6 PID: 1875 Comm: modprobe Not tainted 5.7.0+ #3
[ 4087.203151] Hardware name: LENOVO 10VGCTO1WW/3130, BIOS M1XKT45A 
08/21/2019
[ 4087.203157] RIP: 0010:strlen+0x0/0x20
[ 4087.203160] Code: 48 89 f9 74 09 48 83 c1 01 80 39 00 75 f7 31 d2 44 
0f b6 04 16 44 88 04 11 48 83 c2 01 45 84 c0 75 ee c3 0f 1f 80 00 00 00 
00 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 c3 31
[ 4087.203162] RSP: 0018:ffffa604c090b940 EFLAGS: 00010246
[ 4087.203164] RAX: ffff9a5188735cc0 RBX: ffff9a5188735c40 RCX: 
0000000000000000
[ 4087.203165] RDX: 0000000000000000 RSI: ffffffffc10d4fd8 RDI: 
0000000000000000
[ 4087.203167] RBP: ffffa604c090b9b0 R08: ffff9a51b7bb20a0 R09: 
ffff9a51b6807640
[ 4087.203168] R10: 0000000000000000 R11: 0000000000000001 R12: 
ffff9a5188735cc0
[ 4087.203170] R13: 0000000000000000 R14: ffff9a51acd74710 R15: 
ffff9a519531f000
[ 4087.203172] FS:  00007fd38f2b1540(0000) GS:ffff9a51b7b80000(0000) 
knlGS:0000000000000000
[ 4087.203174] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4087.203175] CR2: 0000000000000000 CR3: 00000001ffc50000 CR4: 
00000000003406e0
[ 4087.203177] Call Trace:
[ 4087.203191]  ? vidtv_channels_init+0x79/0x130 [dvb_vidtv_bridge]
[ 4087.203197]  vidtv_mux_init+0xa6/0x1a0 [dvb_vidtv_bridge]
[ 4087.203201]  vidtv_bridge_probe+0x397/0x400 [dvb_vidtv_bridge]
[ 4087.203205]  ? vidtv_bridge_remove+0x80/0x80 [dvb_vidtv_bridge]
[ 4087.203210]  platform_drv_probe+0x3b/0x80
[ 4087.203213]  really_probe+0x2b3/0x3e0
[ 4087.203216]  driver_probe_device+0xbc/0x100
[ 4087.203218]  device_driver_attach+0x5d/0x70
[ 4087.203220]  __driver_attach+0x8f/0x150
[ 4087.203222]  ? device_driver_attach+0x70/0x70
[ 4087.203225]  bus_for_each_dev+0x7e/0xc0
[ 4087.203227]  driver_attach+0x1e/0x20
[ 4087.203229]  bus_add_driver+0x152/0x1f0
[ 4087.203232]  driver_register+0x74/0xd0
[ 4087.203234]  __platform_driver_register+0x36/0x40
[ 4087.203238]  vidtv_bridge_init+0x31/0x1000 [dvb_vidtv_bridge]
[ 4087.203240]  ? 0xffffffffc0a4a000
[ 4087.203245]  do_one_initcall+0x4a/0x200
[ 4087.203248]  ? kfree+0x231/0x250
[ 4087.203252]  ? _cond_resched+0x19/0x30
[ 4087.203254]  ? kmem_cache_alloc_trace+0x16c/0x240
[ 4087.203258]  do_init_module+0x62/0x250
[ 4087.203260]  load_module+0x2894/0x2af0
[ 4087.203264]  __do_sys_finit_module+0xbe/0x120
[ 4087.203266]  ? __do_sys_finit_module+0xbe/0x120
[ 4087.203269]  __x64_sys_finit_module+0x1a/0x20
[ 4087.203271]  do_syscall_64+0x57/0x1b0
[ 4087.203274]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 4087.203276] RIP: 0033:0x7fd38f3f670d
[ 4087.203278] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 
48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 
05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 53 f7 0c 00 f7 d8 64 89 01 48
[ 4087.203280] RSP: 002b:00007ffe35039d08 EFLAGS: 00000246 ORIG_RAX: 
0000000000000139
[ 4087.203282] RAX: ffffffffffffffda RBX: 000055933c9a7b50 RCX: 
00007fd38f3f670d
[ 4087.203284] RDX: 0000000000000000 RSI: 000055933bacf358 RDI: 
0000000000000003
[ 4087.203285] RBP: 0000000000040000 R08: 0000000000000000 R09: 
0000000000000000
[ 4087.203286] R10: 0000000000000003 R11: 0000000000000246 R12: 
000055933bacf358
[ 4087.203288] R13: 0000000000000000 R14: 000055933c9af3f0 R15: 
000055933c9a7b50
[ 4087.203290] Modules linked in: dvb_vidtv_bridge(+) dvb_vidtv_tuner 
dvb_vidtv_demod dvb_core rfcomm ccm cmac algif_hash algif_skcipher 
af_alg bnep binfmt_misc nls_iso8859_1 edac_mce_amd kvm_amd 
snd_hda_codec_realtek kvm snd_hda_codec_hdmi snd_hda_codec_generic 
ledtrig_audio irqbypass snd_hda_intel snd_intel_dspcfg snd_usb_audio 
amdgpu snd_hda_codec snd_usbmidi_lib mc snd_hda_core snd_hwdep snd_pcm 
snd_seq_midi snd_seq_midi_event btusb snd_rawmidi btrtl btbcm btintel 
bluetooth crct10dif_pclmul ath10k_pci ath10k_core snd_seq ath 
snd_seq_device amd_iommu_v2 snd_timer ghash_clmulni_intel ecdh_generic 
gpu_sched ttm mac80211 aesni_intel drm_kms_helper crypto_simd ecc pl2303 
cryptd glue_helper snd cec input_leds cfg80211 serio_raw i2c_algo_bit 
wmi_bmof fb_sys_fops efi_pstore syscopyarea sysfillrect snd_pci_acp3x 
k10temp ipmi_devintf sysimgblt ccp libarc4 soundcore ipmi_msghandler 
mac_hid sch_fq_codel parport_pc ppdev lp parport drm ip_tables x_tables 
autofs4 hid_generic usbhid hid crc32_pclmul
[ 4087.203325]  ahci psmouse i2c_piix4 libahci nvme nvme_core r8169 
realtek wmi video [last unloaded: dvb_vidtv_bridge]
[ 4087.203335] CR2: 0000000000000000
[ 4087.203337] ---[ end trace c8d767383a27d74e ]---
[ 4087.505440] RIP: 0010:strlen+0x0/0x20
[ 4087.505446] Code: 48 89 f9 74 09 48 83 c1 01 80 39 00 75 f7 31 d2 44 
0f b6 04 16 44 88 04 11 48 83 c2 01 45 84 c0 75 ee c3 0f 1f 80 00 00 00 
00 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 c3 31
[ 4087.505448] RSP: 0018:ffffa604c090b940 EFLAGS: 00010246
[ 4087.505450] RAX: ffff9a5188735cc0 RBX: ffff9a5188735c40 RCX: 
0000000000000000
[ 4087.505452] RDX: 0000000000000000 RSI: ffffffffc10d4fd8 RDI: 
0000000000000000
[ 4087.505453] RBP: ffffa604c090b9b0 R08: ffff9a51b7bb20a0 R09: 
ffff9a51b6807640
[ 4087.505455] R10: 0000000000000000 R11: 0000000000000001 R12: 
ffff9a5188735cc0
[ 4087.505456] R13: 0000000000000000 R14: ffff9a51acd74710 R15: 
ffff9a519531f000
[ 4087.505458] FS:  00007fd38f2b1540(0000) GS:ffff9a51b7b80000(0000) 
knlGS:0000000000000000
[ 4087.505460] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4087.505461] CR2: 0000000000000000 CR3: 00000001ffc50000 CR4: 
00000000003406e0


> diff --git a/arch/Kconfig b/arch/Kconfig
> index 786a85d4ad40d..ddcb4a68ee940 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -868,7 +868,7 @@ config VMAP_STACK
>   	  be enabled.
>   
>   config ARCH_OPTIONAL_KERNEL_RWX
> -	def_bool n
> +	def_bool y
>   
>   config ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>   	def_bool n
> diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> index 80b6a71aa33e4..38c8b848c921f 100644
> --- a/drivers/media/dvb-core/dvbdev.c
> +++ b/drivers/media/dvb-core/dvbdev.c
> @@ -962,6 +962,7 @@ int dvb_usercopy(struct file *file,
>   }
>   
>   #if IS_ENABLED(CONFIG_I2C)
> +#pragma clang optimize off
>   struct i2c_client *dvb_module_probe(const char *module_name,
>   				    const char *name,
>   				    struct i2c_adapter *adap,
> diff --git a/drivers/media/test-drivers/vidtv/Makefile b/drivers/media/test-drivers/vidtv/Makefile
> index 21e50c11c94d0..c99cd13f4adaf 100644
> --- a/drivers/media/test-drivers/vidtv/Makefile
> +++ b/drivers/media/test-drivers/vidtv/Makefile
> @@ -2,5 +2,7 @@
>   
>   dvb-vidtv-tuner-objs := vidtv_tuner.o
>   dvb-vidtv-demod-objs := vidtv_demod.o
> +dvb-vidtv-bridge-objs := vidtv_bridge.o
>   
> -obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o
> +obj-$(CONFIG_DVB_VIDTV)	+= dvb-vidtv-tuner.o dvb-vidtv-demod.o \
> +			   dvb-vidtv-bridge.o
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.c b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
> new file mode 100644
> index 0000000000000..bc1c612c23013
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.c
> @@ -0,0 +1,435 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * The Virtual DTV test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ":%s, %d: " fmt, __func__, __LINE__
> +
> +#include <linux/moduleparam.h>
> +#include <linux/mutex.h>
> +#include <linux/platform_device.h>
> +#include <linux/printk.h>
> +#include <linux/time.h>
> +#include <linux/types.h>
> +#include <linux/workqueue.h>
> +
> +#include "vidtv_bridge.h"
> +#include "vidtv_demod.h"
> +#include "vidtv_tuner.h"
> +
> +#define TUNER_DEFAULT_ADDR 0x68
> +#define DEMOD_DEFAULT_ADDR 0x60
> +
> +static unsigned int drop_tslock_prob_on_low_snr;
> +module_param(drop_tslock_prob_on_low_snr, uint, 0);
> +MODULE_PARM_DESC(drop_tslock_prob_on_low_snr,
> +		 "Probability of losing the TS lock if the signal quality is bad");
> +
> +static unsigned int recover_tslock_prob_on_good_snr;
> +module_param(recover_tslock_prob_on_good_snr, uint, 0);
> +MODULE_PARM_DESC(recover_tslock_prob_on_good_snr,
> +		 "Probability recovering the TS lock when the signal improves");
> +
> +static unsigned int mock_power_up_delay_msec;
> +module_param(mock_power_up_delay_msec, uint, 0);
> +MODULE_PARM_DESC(mock_power_up_delay_msec, "Simulate a power up delay");
> +
> +static unsigned int mock_tune_delay_msec;
> +module_param(mock_tune_delay_msec, uint, 0);
> +MODULE_PARM_DESC(mock_tune_delay_msec, "Simulate a tune delay");
> +
> +static unsigned int vidtv_valid_dvb_t_freqs[8];
> +module_param_array(vidtv_valid_dvb_t_freqs, uint, NULL, 0);
> +MODULE_PARM_DESC(vidtv_valid_dvb_t_freqs,
> +		 "Valid DVB-T frequencies to simulate");
> +
> +static unsigned int vidtv_valid_dvb_c_freqs[8];
> +module_param_array(vidtv_valid_dvb_c_freqs, uint, NULL, 0);
> +MODULE_PARM_DESC(vidtv_valid_dvb_c_freqs,
> +		 "Valid DVB-C frequencies to simulate");
> +
> +static unsigned int vidtv_valid_dvb_s_freqs[8];
> +module_param_array(vidtv_valid_dvb_s_freqs, uint, NULL, 0);
> +MODULE_PARM_DESC(vidtv_valid_dvb_s_freqs,
> +		 "Valid DVB-C frequencies to simulate");
> +
> +static unsigned int max_frequency_shift_hz;
> +module_param(max_frequency_shift_hz, uint, 0);
> +MODULE_PARM_DESC(max_frequency_shift_hz,
> +		 "Maximum shift in HZ allowed when tuning in a channel");
> +
> +DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nums);
> +
> +static int vidtv_start_streaming(struct vidtv_dvb *dvb)
> +{
> +	if (dvb->streaming) {
> +		pr_warn_ratelimited("Already streaming. Skipping.\n");
> +		return 0;
> +	}
> +
> +	dvb->streaming = true;
> +	return 0;
> +}
> +
> +static int vidtv_stop_streaming(struct vidtv_dvb *dvb)
> +{
> +	dvb->streaming = false;
> +
> +	return 0;
> +}
> +
> +static int vidtv_start_feed(struct dvb_demux_feed *feed)
> +{
> +	struct dvb_demux *demux = feed->demux;
> +	struct vidtv_dvb *dvb   = demux->priv;
> +	int rc;
> +	int ret;
> +
> +	if (!demux->dmx.frontend)
> +		return -EINVAL;
> +
> +	mutex_lock(&dvb->feed_lock);
> +
> +	dvb->nfeeds++;
> +	rc = dvb->nfeeds;
> +
> +	if (dvb->nfeeds == 1) {
> +		ret = vidtv_start_streaming(dvb);
> +		if (ret < 0)
> +			rc = ret;
> +	}
> +
> +	mutex_unlock(&dvb->feed_lock);
> +	return rc;
> +}
> +
> +static int vidtv_stop_feed(struct dvb_demux_feed *feed)
> +{
> +	struct dvb_demux *demux = feed->demux;
> +	struct vidtv_dvb *dvb   = demux->priv;
> +	int    err              = 0;
> +
> +	mutex_lock(&dvb->feed_lock);
> +	dvb->nfeeds--;
> +
> +	if (!dvb->nfeeds)
> +		err = vidtv_stop_streaming(dvb);
> +
> +	mutex_unlock(&dvb->feed_lock);
> +	return err;
> +}
> +
> +static struct dvb_frontend *vidtv_get_frontend_ptr(struct i2c_client *c)
> +{
> +	/* the demod will set this when its probe function runs */
> +	struct vidtv_demod_state *state = i2c_get_clientdata(c);
> +
> +	return &state->frontend;
> +}
> +
> +static int vidtv_master_xfer(struct i2c_adapter *i2c_adap,
> +			     struct i2c_msg msgs[],
> +			     int num)
> +{
> +	return 0;
> +}
> +
> +static u32 vidtv_i2c_func(struct i2c_adapter *adapter)
> +{
> +	return I2C_FUNC_I2C;
> +}
> +
> +static const struct i2c_algorithm vidtv_i2c_algorithm = {
> +	.master_xfer   = vidtv_master_xfer,
> +	.functionality = vidtv_i2c_func,
> +};
> +
> +static int vidtv_bridge_i2c_register_adap(struct vidtv_dvb *dvb)
> +{
> +	struct i2c_adapter *i2c_adapter = &dvb->i2c_adapter;
> +
> +	strscpy(i2c_adapter->name, "vidtv_i2c", sizeof(i2c_adapter->name));
> +	i2c_adapter->owner      = THIS_MODULE;
> +	i2c_adapter->algo       = &vidtv_i2c_algorithm;
> +	i2c_adapter->algo_data  = NULL;
> +	i2c_adapter->timeout    = 500;
> +	i2c_adapter->retries    = 3;
> +	i2c_adapter->dev.parent = &dvb->pdev->dev;
> +
> +	i2c_set_adapdata(i2c_adapter, dvb);
> +	return i2c_add_adapter(&dvb->i2c_adapter);
> +}
> +
> +static int vidtv_bridge_register_adap(struct vidtv_dvb *dvb)
> +{
> +	int ret = 0;
> +
> +	ret = dvb_register_adapter(&dvb->adapter,
> +				   KBUILD_MODNAME,
> +				   THIS_MODULE,
> +				   &dvb->i2c_adapter.dev,
> +				   adapter_nums);
> +
> +	return ret;
> +}
> +
> +static int vidtv_bridge_dmx_init(struct vidtv_dvb *dvb)
> +{
> +	dvb->demux.dmx.capabilities = DMX_TS_FILTERING |
> +				      DMX_SECTION_FILTERING;
> +
> +	dvb->demux.priv       = dvb;
> +	dvb->demux.filternum  = 256;
> +	dvb->demux.feednum    = 256;
> +	dvb->demux.start_feed = vidtv_start_feed;
> +	dvb->demux.stop_feed  = vidtv_stop_feed;
> +
> +	return dvb_dmx_init(&dvb->demux);
> +}
> +
> +static int vidtv_bridge_dmxdev_init(struct vidtv_dvb *dvb)
> +{
> +	dvb->dmx_dev.filternum    = 256;
> +	dvb->dmx_dev.demux        = &dvb->demux.dmx;
> +	dvb->dmx_dev.capabilities = 0;
> +
> +	return dvb_dmxdev_init(&dvb->dmx_dev, &dvb->adapter);
> +}
> +
> +static int vidtv_bridge_probe_demod(struct vidtv_dvb *dvb, u32 n)
> +{
> +	struct vidtv_demod_config cfg = {};
> +
> +	cfg.drop_tslock_prob_on_low_snr     = drop_tslock_prob_on_low_snr;
> +	cfg.recover_tslock_prob_on_good_snr = recover_tslock_prob_on_good_snr;
> +
> +	dvb->i2c_client_demod[n] = dvb_module_probe("vidtv_demod",
> +						    NULL,
> +						    &dvb->i2c_adapter,
> +						    DEMOD_DEFAULT_ADDR,
> +						    &cfg);
> +
> +	/* driver will not work anyways so bail out */
> +	if (!dvb->i2c_client_demod[n])
> +		return -ENODEV;
> +
> +	/* retrieve a ptr to the frontend state */
> +	dvb->fe[n] = vidtv_get_frontend_ptr(dvb->i2c_client_demod[n]);
> +
> +	return 0;
> +}
> +
> +static int vidtv_bridge_probe_tuner(struct vidtv_dvb *dvb, u32 n)
> +{
> +	struct vidtv_tuner_config cfg = {};
> +
> +	cfg.fe                       = dvb->fe[n];
> +	cfg.mock_power_up_delay_msec = mock_power_up_delay_msec;
> +	cfg.mock_tune_delay_msec     = mock_tune_delay_msec;
> +
> +	memcpy(cfg.vidtv_valid_dvb_t_freqs,
> +	       vidtv_valid_dvb_t_freqs,
> +	       sizeof(vidtv_valid_dvb_t_freqs));
> +
> +	memcpy(cfg.vidtv_valid_dvb_c_freqs,
> +	       vidtv_valid_dvb_c_freqs,
> +	       sizeof(vidtv_valid_dvb_c_freqs));
> +
> +	memcpy(cfg.vidtv_valid_dvb_s_freqs,
> +	       vidtv_valid_dvb_s_freqs,
> +	       sizeof(vidtv_valid_dvb_s_freqs));
> +
> +	cfg.max_frequency_shift_hz = max_frequency_shift_hz;
> +
> +	dvb->i2c_client_tuner[n] = dvb_module_probe("vidtv_tuner",
> +						    NULL,
> +						    &dvb->i2c_adapter,
> +						    TUNER_DEFAULT_ADDR,
> +						    &cfg);
> +
> +	return (dvb->i2c_client_tuner[n]) ? 0 : -ENODEV;
> +}
> +
> +static int vidtv_bridge_dvb_init(struct vidtv_dvb *dvb)
> +{
> +	int ret;
> +	int i;
> +	int j;
> +	int k;
> +	int w;
> +	int l;
> +
> +	ret = vidtv_bridge_i2c_register_adap(dvb);
> +	if (ret < 0)
> +		goto fail_i2c;
> +
> +	ret = vidtv_bridge_register_adap(dvb);
> +	if (ret < 0)
> +		goto fail_adapter;
> +
> +	for (i = 0; i < NUM_FE; ++i) {
> +		ret = vidtv_bridge_probe_demod(dvb, i);
> +		if (ret < 0)
> +			goto fail_demod_probe;
> +
> +		ret = vidtv_bridge_probe_tuner(dvb, i);
> +		if (ret < 0)
> +			goto fail_tuner_probe;
> +
> +		ret = dvb_register_frontend(&dvb->adapter, dvb->fe[i]);
> +		if (ret < 0)
> +			goto fail_fe;
> +	}
> +
> +	ret = vidtv_bridge_dmx_init(dvb);
> +	if (ret < 0)
> +		goto fail_dmx;
> +
> +	ret = vidtv_bridge_dmxdev_init(dvb);
> +	if (ret < 0)
> +		goto fail_dmx_dev;
> +
> +	for (j = 0; j < NUM_FE; ++j) {
> +		ret = dvb->demux.dmx.connect_frontend(&dvb->demux.dmx,
> +						      &dvb->dmx_fe[j]);
> +		if (ret < 0)
> +			goto fail_dmx_conn;
> +
> +		/*
> +		 * The source of the demux is a frontend connected
> +		 * to the demux.
> +		 */
> +		dvb->dmx_fe[j].source = DMX_FRONTEND_0;
> +	}
> +
> +	return ret;
> +
> +fail_dmx_conn:
> +	for (j = j - 1; j >= 0; --j)
> +		dvb->demux.dmx.remove_frontend(&dvb->demux.dmx,
> +					       &dvb->dmx_fe[j]);
> +fail_dmx_dev:
> +	dvb_dmxdev_release(&dvb->dmx_dev);
> +fail_dmx:
> +	dvb_dmx_release(&dvb->demux);
> +fail_fe:
> +	for (k = i; k >= 0; --k)
> +		dvb_unregister_frontend(dvb->fe[k]);
> +fail_tuner_probe:
> +	for (w = i; w >= 0; --w)
> +		dvb_module_release(dvb->i2c_client_tuner[w]);
> +
> +fail_demod_probe:
> +	for (l = i; l >= 0; --l)
> +		dvb_module_release(dvb->i2c_client_demod[l]);
> +
> +fail_adapter:
> +	dvb_unregister_adapter(&dvb->adapter);
> +
> +fail_i2c:
> +	i2c_del_adapter(&dvb->i2c_adapter);
> +
> +	return ret;
> +}
> +
> +static int vidtv_bridge_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct vidtv_dvb *dvb;
> +
> +	dvb = kzalloc(sizeof(*dvb), GFP_KERNEL);
> +	if (!dvb)
> +		return -ENOMEM;
> +
> +	dvb->pdev = pdev;
> +
> +	ret = vidtv_bridge_dvb_init(dvb);
> +	if (ret < 0)
> +		goto err_dvb;
> +
> +	mutex_init(&dvb->feed_lock);
> +
> +	platform_set_drvdata(pdev, dvb);
> +
> +	return ret;
> +
> +err_dvb:
> +	kfree(dvb);
> +	return ret;
> +}
> +
> +static int vidtv_bridge_remove(struct platform_device *pdev)
> +{
> +	struct vidtv_dvb *dvb;
> +	u32 i;
> +
> +	dvb = platform_get_drvdata(pdev);
> +
> +	mutex_destroy(&dvb->feed_lock);
> +
> +	for (i = 0; i < NUM_FE; ++i)

Using i++ is more common though

> +		dvb->demux.dmx.remove_frontend(&dvb->demux.dmx,
> +					       &dvb->dmx_fe[i]);
> +
> +	dvb_dmxdev_release(&dvb->dmx_dev);
> +	dvb_dmx_release(&dvb->demux);
> +
> +	for (i = 0; i < NUM_FE; ++i) {
> +		dvb_unregister_frontend(dvb->fe[i]);
> +		dvb_frontend_detach(dvb->fe[i]);
> +	}
> +

Where do you release tuner and demod? probe is happening
from vidtv_bridge_dvb_init(). Don't you have to do the
reverse here?

> +	dvb_unregister_adapter(&dvb->adapter);

Don't you have to do i2c_del_adapter() here?
> +
> +	return 0;
> +}
> +
> +static void vidtv_bridge_dev_release(struct device *dev)
> +{
> +}
> +
> +static struct platform_device vidtv_bridge_dev = {
> +	.name		= "vidtv_bridge",
> +	.dev.release	= vidtv_bridge_dev_release,
> +};
> +
> +static struct platform_driver vidtv_bridge_driver = {
> +	.driver = {
> +		.name                = "vidtv_bridge",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe    = vidtv_bridge_probe,
> +	.remove   = vidtv_bridge_remove,
> +};
> +
> +static void __exit vidtv_bridge_exit(void)
> +{
> +	platform_driver_unregister(&vidtv_bridge_driver);
> +	platform_device_unregister(&vidtv_bridge_dev);
> +}
> +
> +static int __init vidtv_bridge_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_device_register(&vidtv_bridge_dev);
> +	if (ret)
> +		return ret;
> +
> +	ret = platform_driver_register(&vidtv_bridge_driver);
> +	if (ret)
> +		platform_device_unregister(&vidtv_bridge_dev);
> +
> +	return ret;
> +}
> +
> +module_init(vidtv_bridge_init);
> +module_exit(vidtv_bridge_exit);
> +
> +MODULE_DESCRIPTION("Virtual Digital TV Test Driver");
> +MODULE_AUTHOR("Daniel W. S. Almeida");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/media/test-drivers/vidtv/vidtv_bridge.h b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
> new file mode 100644
> index 0000000000000..4931bfb73273c
> --- /dev/null
> +++ b/drivers/media/test-drivers/vidtv/vidtv_bridge.h
> @@ -0,0 +1,39 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * The Virtual DTV test driver serves as a reference DVB driver and helps
> + * validate the existing APIs in the media subsystem. It can also aid
> + * developers working on userspace applications.
> + *
> + * Written by Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> + */
> +
> +#ifndef VIDTV_BRIDGE_H
> +#define VIDTV_BRIDGE_H
> +
> +#define NUM_FE 1
> +
> +#include <linux/i2c.h>
> +#include <linux/platform_device.h>
> +#include <linux/types.h>
> +#include <media/dmxdev.h>
> +#include <media/dvb_demux.h>
> +#include <media/dvb_frontend.h>
> +
> +struct vidtv_dvb {
> +	struct platform_device *pdev;
> +	struct dvb_frontend *fe[NUM_FE];
> +	struct dvb_adapter adapter;
> +	struct dvb_demux demux;
> +	struct dmxdev dmx_dev;
> +	struct dmx_frontend dmx_fe[NUM_FE];
> +	struct i2c_adapter i2c_adapter;
> +	struct i2c_client *i2c_client_demod[NUM_FE];
> +	struct i2c_client *i2c_client_tuner[NUM_FE];
> +
> +	u32 nfeeds;
> +	struct mutex feed_lock; /* start/stop feed */
> +
> +	bool streaming;
> +};
> +
> +#endif // VIDTV_BRIDG_H
> 

thanks,
-- Shuah
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Re: [Linux-kernel-mentees] [RFC, WIP, v6 02/10] media: vidtv: implement a tuner driver

[Daniel W. S. Almeida]

Hi Shuah, thanks for reviewing this!

>> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 
> Are you using git send-email to send patches. Why do have this
> From line in here? Same comment on all other patches in this series.

I am using 'git format-patch --to=[...] --cc=[...]' and then 'git send-email'.

Git format-patch usually adds these two lines for every patch it generates:
  1 From f966b0ea574a36b96ddfb8a8a716b174bc150eba Mon Sep 17 00:00:00 2001
  2 From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>

I have no idea whether these are necessary, so I just leave them there :)
The first line is specially weird.


As for this:

>> +	switch (c->delivery_system) {
> 
> Add indetation for the below:
> 
>> +	case SYS_DVBT:
>> +	case SYS_DVBT2:
>> +		valid_freqs = config.vidtv_valid_dvb_t_freqs;
>> +		array_sz    = ARRAY_SIZE(config.vidtv_valid_dvb_t_freqs);
>> +		break;

I am not sure I understand. Indenting the case statements leads to a
checkpatch complaint: 

>SWITCH_CASE_INDENT_LEVEL: switch and case should be at the
>same indent

And the actual statements under 'case' are already indented.

Thanks
- Daniel
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