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S. Almeida" X-Google-Original-From: Daniel W. S. Almeida To: mchehab+huawei@kernel.org, sean@mess.org, kstewart@linuxfoundation.org, allison@lohutok.net, tglx@linutronix.de Date: Thu, 30 Jul 2020 12:34:57 -0300 Message-Id: <20200730153501.742993-1-dwlsalmeida@gmail.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Cc: linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, "Daniel W . S . Almeida" , linux-media@vger.kernel.org Subject: [Linux-kernel-mentees] [v8 0/4] media: vidtv: Implement a virtual DVB driver X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" From: Daniel W. S. Almeida 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 Current state for this driver: - Driver is modprobed without any errors on dmesg - Using dvbv5-scan does not cause the driver to crash - Driver feeds the demux with TS packets (PSI, PCR, AES3 audio and NULL packets for padding), but the stream is not valid yet. - Kmemleak shows no leaks. UBSAN & KASAN pick up some bugs The Virtual Digital TV Driver (vidtv) Background ---------- Vidtv is a virtual DVB driver that aims to serve as a reference for driver writers by serving as a template. It also validates the existing media DVB APIs, thus helping userspace application writers. Currently, it consists of: - A fake tuner driver, which will report a bad signal quality if the chosen frequency is too far away from a table of valid frequencies for a particular delivery system. - A fake demod driver, which will constantly poll the fake signal quality returned by the tuner, simulating a device that can lose/reacquire a lock on the signal depending on the CNR levels. - A fake bridge driver, which is the module responsible for modprobing the fake tuner and demod modules and implementing the demux logic. This module takes parameters at initialization that will dictate how the simulation behaves. - Code reponsible for encoding a valid MPEG Transport Stream, which is then passed to the bridge driver. This fake stream contains some hardcoded content. For now, we have a single, audio-only channel containing a single MPEG Elementary Stream, which in turn contains a SMPTE 302m encoded sine-wave. Note that this particular encoder was chosen because it is the easiest way to encode PCM audio data in a MPEG Transport Stream. Building vidtv -------------- vidtv is a test driver and thus is **not** enabled by default when compiling the kernel. In order to enable compilation of vidtv: - Enable **DVB_TEST_DRIVERS**, then - Enable **DVB_VIDTV** When compiled as a module, expect the following .ko files: - dvb_vidtv_tuner.ko - dvb_vidtv_demod.ko - dvb_vidtv_bridge.ko Running vidtv ------------- When compiled as a module, run:: modprobe dvb_vidtv_bridge That's it! The bridge driver will initialize the tuner and demod drivers as part of its own initialization. You can optionally define some command-line arguments to vidtv, see the documentation for more info. Testing vidtv with v4l-utils ============================ Start by installing v4l-utils and then modprobing vidtv:: modprobe dvb_vidtv_bridge If the driver is OK, it should load and its probing code will run. This will pull in the tuner and demod drivers. Using dvb-fe-tool ----------------- The first step to check whether the demod loaded successfully is to run:: $ dvb-fe-tool This should return what is currently set up at the demod struct, i.e.:: 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_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, } .... Using dvb-scan -------------- In order to tune into a channel and read the PSI tables, we can use dvb-scan. For this, one should provide a configuration file known as a 'scan file', here's an example:: [Channel] FREQUENCY = 330000000 MODULATION = QAM/AUTO SYMBOL_RATE = 6940000 INNER_FEC = AUTO DELIVERY_SYSTEM = DVBC/ANNEX_A NOTE: The parameters depend on the video standard you're testing. NOTE: Vidtv is a fake driver and does not validate much of the information in the scan file. Just specifying 'FREQUENCY' and 'DELIVERY_SYSTEM' should be enough for DVB-T/DVB-T2. For DVB-S/DVB-C however, you should also provide 'SYMBOL_RATE'. Assuming this channel is named 'channel.conf', you can then run:: $ dvbv5-scan dresden_dvbc_channel.conf Using dvb-zap ------------- dvbv5-zap is a command line tool that can be used to record MPEG-TS to disk. The typical use is to tune into a channel and put it into record mode. The example below - which is taken from the documentation - illustrates that:: $ dvbv5-zap -c dvb_channel.conf "trilhas sonoras" -r using demux '/dev/dvb/adapter0/demux0' reading channels from file 'dvb_channel.conf' service has pid type 05: 204 tuning to 573000000 Hz audio pid 104 dvb_set_pesfilter 104 Lock (0x1f) Quality= Good Signal= 100.00% C/N= -13.80dB UCB= 70 postBER= 3.14x10^-3 PER= 0 DVR interface '/dev/dvb/adapter0/dvr0' can now be opened The channel can be watched by playing the contents of the DVR interface, with some player that recognizes the MPEG-TS format, such as *mplayer* or *vlc*. By playing the contents of the stream one can visually inspect the workings of vidtv, e.g.:: $ mplayer /dev/dvb/adapter0/dvr0 Daniel W. S. Almeida (4): media: vidtv: implement a tuner driver media: vidtv: implement a demodulator driver media: vidtv: add a bridge driver media: Documentation: vidtv: Add ReST documentation for vidtv .../driver-api/media/drivers/index.rst | 1 + .../driver-api/media/drivers/vidtv.rst | 417 ++++++ MAINTAINERS | 8 + drivers/media/test-drivers/Kconfig | 16 + 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 | 547 ++++++++ .../media/test-drivers/vidtv/vidtv_bridge.h | 60 + .../media/test-drivers/vidtv/vidtv_channel.c | 360 ++++++ .../media/test-drivers/vidtv/vidtv_channel.h | 82 ++ .../media/test-drivers/vidtv/vidtv_common.c | 90 ++ .../media/test-drivers/vidtv/vidtv_common.h | 33 + .../media/test-drivers/vidtv/vidtv_demod.c | 440 +++++++ .../media/test-drivers/vidtv/vidtv_demod.h | 73 ++ .../media/test-drivers/vidtv/vidtv_encoder.h | 99 ++ drivers/media/test-drivers/vidtv/vidtv_mux.c | 454 +++++++ drivers/media/test-drivers/vidtv/vidtv_mux.h | 154 +++ drivers/media/test-drivers/vidtv/vidtv_pes.c | 434 +++++++ drivers/media/test-drivers/vidtv/vidtv_pes.h | 243 ++++ drivers/media/test-drivers/vidtv/vidtv_psi.c | 1131 +++++++++++++++++ drivers/media/test-drivers/vidtv/vidtv_psi.h | 686 ++++++++++ .../media/test-drivers/vidtv/vidtv_s302m.c | 663 ++++++++++ .../media/test-drivers/vidtv/vidtv_s302m.h | 136 ++ drivers/media/test-drivers/vidtv/vidtv_ts.c | 147 +++ drivers/media/test-drivers/vidtv/vidtv_ts.h | 138 ++ .../media/test-drivers/vidtv/vidtv_tuner.c | 427 +++++++ .../media/test-drivers/vidtv/vidtv_tuner.h | 43 + 28 files changed, 6903 insertions(+) create mode 100644 Documentation/driver-api/media/drivers/vidtv.rst 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 -- 2.27.0 _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees