[PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[Daniel W. S. Almeida]

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

Implement a dummy DVB tuner as part of ongoing work
on a virtual DVB test driver under the 2020 Spring Linux
Kernel Mentorship Program.

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.

For now, only a basic skeleton is available, most functions do nothing
whatsoever.

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

Changes in v2:
	Commit message was rewritten
	Added better description in KConfig
	Added better description in .h and .c
	Added copyright notice in .h and .c
	Kconfig dummy tuner option now defaults to 'n'
	Removed calls to pr_err, pr_debug
Not addressed in v2:
	attach()/release() calls:
		I would appreciate some clarification on this, since some
		tuners implement only probe()/remove(), some implement
		only attach()/release() and some implement both (e.g. mt2060.c).
		Furthermore, in mt2060.c, both attach() and probe()  copy 
		struct dvb_tuner_ops into fe->ops->tuner_ops.

-------------------------------------------------------------

 drivers/media/tuners/Kconfig           |   9 ++
 drivers/media/tuners/Makefile          |   1 +
 drivers/media/tuners/dvb_dummy_tuner.c | 160 +++++++++++++++++++++++++
 drivers/media/tuners/dvb_dummy_tuner.h |  31 +++++
 4 files changed, 201 insertions(+)
 create mode 100644 drivers/media/tuners/dvb_dummy_tuner.c
 create mode 100644 drivers/media/tuners/dvb_dummy_tuner.h

diff --git a/drivers/media/tuners/Kconfig b/drivers/media/tuners/Kconfig
index e104bb7766e1..d433dc7e68b1 100644
--- a/drivers/media/tuners/Kconfig
+++ b/drivers/media/tuners/Kconfig
@@ -296,4 +296,13 @@ config MEDIA_TUNER_QM1D1B0004
 	default m if !MEDIA_SUBDRV_AUTOSELECT
 	help
 	  Sharp QM1D1B0004 ISDB-S tuner driver.
+
+config MEDIA_TUNER_DVB_DUMMY_TUNER
+	tristate "Dummy tuner"
+	depends on MEDIA_SUPPORT && I2C
+	default n
+	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.
 endmenu
diff --git a/drivers/media/tuners/Makefile b/drivers/media/tuners/Makefile
index 7b4f8423501e..f98de1cf2e19 100644
--- a/drivers/media/tuners/Makefile
+++ b/drivers/media/tuners/Makefile
@@ -44,5 +44,6 @@ obj-$(CONFIG_MEDIA_TUNER_QM1D1C0042) += qm1d1c0042.o
 obj-$(CONFIG_MEDIA_TUNER_QM1D1B0004) += qm1d1b0004.o
 obj-$(CONFIG_MEDIA_TUNER_M88RS6000T) += m88rs6000t.o
 obj-$(CONFIG_MEDIA_TUNER_TDA18250) += tda18250.o
+obj-$(CONFIG_MEDIA_TUNER_DVB_DUMMY_TUNER) += dvb_dummy_tuner.o
 
 ccflags-y += -I$(srctree)/drivers/media/dvb-frontends
diff --git a/drivers/media/tuners/dvb_dummy_tuner.c b/drivers/media/tuners/dvb_dummy_tuner.c
new file mode 100644
index 000000000000..8aed5d583eeb
--- /dev/null
+++ b/drivers/media/tuners/dvb_dummy_tuner.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * A dummy DVB tuner as part of ongoing work
+ * on a virtual DVB test driver under the 2020 Spring Linux
+ * Kernel Mentorship Program.
+ *
+ * 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.
+ *
+ * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#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 "dvb_dummy_tuner.h"
+
+struct dvb_dummy_tuner_dev {
+	struct dvb_frontend *fe;
+};
+
+static void dvb_dummy_tuner_release(struct dvb_frontend *fe)
+{
+}
+
+static int dvb_dummy_tuner_init(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_sleep(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_suspend(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_resume(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_set_params(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_set_config(struct dvb_frontend *fe, void *priv_cfg)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_get_frequency(struct dvb_frontend *fe,
+					 u32 *frequency)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_get_bandwidth(struct dvb_frontend *fe,
+					 u32 *bandwidth)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_get_if_frequency(struct dvb_frontend *fe,
+					    u32 *frequency)
+{
+	return 0;
+}
+
+static int dvb_dummy_tuner_get_status(struct dvb_frontend *fe, u32 *status)
+{
+	return 0;
+}
+
+static const struct dvb_tuner_ops dvb_dummy_tuner_ops = {
+	.release = dvb_dummy_tuner_release,
+	.init = dvb_dummy_tuner_init,
+	.sleep = dvb_dummy_tuner_sleep,
+	.suspend = dvb_dummy_tuner_suspend,
+	.resume = dvb_dummy_tuner_resume,
+	.set_params = dvb_dummy_tuner_set_params,
+	.set_config = dvb_dummy_tuner_set_config,
+	.get_bandwidth = dvb_dummy_tuner_get_bandwidth,
+	.get_frequency = dvb_dummy_tuner_get_frequency,
+	.get_if_frequency = dvb_dummy_tuner_get_if_frequency,
+	.get_status = dvb_dummy_tuner_get_status,
+};
+
+static const struct i2c_device_id dvb_dummy_tuner_i2c_id_table[] = {
+	{"dvb_dummy_tuner", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, dvb_dummy_tuner_i2c_id_table);
+
+static int dvb_dummy_tuner_i2c_probe(struct i2c_client *client,
+				     const struct i2c_device_id *id)
+{
+	int ret = 0;
+	struct dvb_dummy_tuner_config *config = client->dev.platform_data;
+	struct dvb_frontend *fe = config->fe;
+	struct dvb_dummy_tuner_dev *tuner_dev = NULL;
+
+	tuner_dev = kzalloc(sizeof(*tuner_dev), GFP_KERNEL);
+	if (!tuner_dev) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	i2c_set_clientdata(client, tuner_dev);
+	tuner_dev->fe = config->fe;
+
+	memcpy(&fe->ops.tuner_ops,
+	       &dvb_dummy_tuner_ops,
+	       sizeof(struct dvb_tuner_ops));
+
+	fe->tuner_priv = client;
+
+	return ret;
+
+err:
+	return ret;
+}
+
+static int dvb_dummy_tuner_i2c_remove(struct i2c_client *client)
+{
+	struct dvb_dummy_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 dvb_dummy_tuner_i2c_driver = {
+	.driver = {
+		.name = "dvb_dummy_tuner",
+		.suppress_bind_attrs = true,
+	},
+	.probe		= dvb_dummy_tuner_i2c_probe,
+	.remove		= dvb_dummy_tuner_i2c_remove,
+	.id_table	= dvb_dummy_tuner_i2c_id_table,
+};
+module_i2c_driver(dvb_dummy_tuner_i2c_driver);
+
+MODULE_DESCRIPTION("DVB Dummy Tuner");
+MODULE_AUTHOR("Daniel W. S. Almeida");
+MODULE_LICENSE("GPL");
diff --git a/drivers/media/tuners/dvb_dummy_tuner.h b/drivers/media/tuners/dvb_dummy_tuner.h
new file mode 100644
index 000000000000..3569bbc3716e
--- /dev/null
+++ b/drivers/media/tuners/dvb_dummy_tuner.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * A dummy DVB tuner as part of ongoing work
+ * on a virtual DVB test driver under the 2020 Spring Linux
+ * Kernel Mentorship Program.
+ *
+ * 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.
+ *
+ * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>
+ */
+
+#ifndef __TUNER_DVB_DUMMY_TUNER_H__
+#define __TUNER_DVB_DUMMY_TUNER_H__
+
+#include <media/dvb_frontend.h>
+/**
+ * struct dvb_dummy_tuner_config - configuration parameters for the dummy tuner
+ *
+ * @fe:
+ *	frontend returned by driver
+ */
+struct dvb_dummy_tuner_config {
+	struct dvb_frontend *fe;
+};
+
+#endif /*__TUNER_DVB_DUMMY_TUNER_H__ */
-- 
2.24.1

Re: [PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[Shuah Khan]

On 1/9/20 4:37 PM, Daniel W. S. Almeida wrote:
> From: "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>
> 

> Implement a dummy DVB tuner as part of ongoing work
> on a virtual DVB test driver under the 2020 Spring Linux
> Kernel Mentorship Program.
> 

Get rid of the above. Not relevant for the patch. No need to spin
v3 just for this change and you can make the with other changes
as you get comments from others.

> 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.
> 
> For now, only a basic skeleton is available, most functions do nothing
> whatsoever.
> 
> Signed-off-by: Daniel W. S. Almeida <dwlsalmeida@gmail.com>

thanks,
-- Shuah

Re: [PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[Greg KH]

On Thu, Jan 09, 2020 at 08:37:57PM -0300, Daniel W. S. Almeida wrote:
> +config MEDIA_TUNER_DVB_DUMMY_TUNER
> +	tristate "Dummy tuner"

"Dummy DVB Media Tuner" perhaps?

> +	depends on MEDIA_SUPPORT && I2C
> +	default n

"default n" is always the default, no need to list it again here.

> +	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.

A bit of text here saying what the module name would be is always nice,
see other Kconfig entries for the normal text needed.

>  endmenu
> diff --git a/drivers/media/tuners/Makefile b/drivers/media/tuners/Makefile
> index 7b4f8423501e..f98de1cf2e19 100644
> --- a/drivers/media/tuners/Makefile
> +++ b/drivers/media/tuners/Makefile
> @@ -44,5 +44,6 @@ obj-$(CONFIG_MEDIA_TUNER_QM1D1C0042) += qm1d1c0042.o
>  obj-$(CONFIG_MEDIA_TUNER_QM1D1B0004) += qm1d1b0004.o
>  obj-$(CONFIG_MEDIA_TUNER_M88RS6000T) += m88rs6000t.o
>  obj-$(CONFIG_MEDIA_TUNER_TDA18250) += tda18250.o
> +obj-$(CONFIG_MEDIA_TUNER_DVB_DUMMY_TUNER) += dvb_dummy_tuner.o
>  
>  ccflags-y += -I$(srctree)/drivers/media/dvb-frontends
> diff --git a/drivers/media/tuners/dvb_dummy_tuner.c b/drivers/media/tuners/dvb_dummy_tuner.c
> new file mode 100644
> index 000000000000..8aed5d583eeb
> --- /dev/null
> +++ b/drivers/media/tuners/dvb_dummy_tuner.c
> @@ -0,0 +1,160 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later

I have to ask, are you _SURE_ you want "GPL 2+" here?


> +/*
> + * A dummy DVB tuner as part of ongoing work
> + * on a virtual DVB test driver under the 2020 Spring Linux
> + * Kernel Mentorship Program.

No need for saying why it was written in the file like this :)

> + *
> + * 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.
> + *
> + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>

Normally this is the first comment line above in this block.

> + */
> +
> +#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 "dvb_dummy_tuner.h"
> +
> +struct dvb_dummy_tuner_dev {
> +	struct dvb_frontend *fe;
> +};
> +
> +static void dvb_dummy_tuner_release(struct dvb_frontend *fe)
> +{
> +}
> +
> +static int dvb_dummy_tuner_init(struct dvb_frontend *fe)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_sleep(struct dvb_frontend *fe)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_suspend(struct dvb_frontend *fe)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_resume(struct dvb_frontend *fe)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_set_params(struct dvb_frontend *fe)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_set_config(struct dvb_frontend *fe, void *priv_cfg)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_frequency(struct dvb_frontend *fe,
> +					 u32 *frequency)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_bandwidth(struct dvb_frontend *fe,
> +					 u32 *bandwidth)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_if_frequency(struct dvb_frontend *fe,
> +					    u32 *frequency)
> +{
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_status(struct dvb_frontend *fe, u32 *status)
> +{
> +	return 0;
> +}
> +
> +static const struct dvb_tuner_ops dvb_dummy_tuner_ops = {
> +	.release = dvb_dummy_tuner_release,
> +	.init = dvb_dummy_tuner_init,
> +	.sleep = dvb_dummy_tuner_sleep,
> +	.suspend = dvb_dummy_tuner_suspend,
> +	.resume = dvb_dummy_tuner_resume,
> +	.set_params = dvb_dummy_tuner_set_params,
> +	.set_config = dvb_dummy_tuner_set_config,
> +	.get_bandwidth = dvb_dummy_tuner_get_bandwidth,
> +	.get_frequency = dvb_dummy_tuner_get_frequency,
> +	.get_if_frequency = dvb_dummy_tuner_get_if_frequency,
> +	.get_status = dvb_dummy_tuner_get_status,
> +};
> +
> +static const struct i2c_device_id dvb_dummy_tuner_i2c_id_table[] = {
> +	{"dvb_dummy_tuner", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, dvb_dummy_tuner_i2c_id_table);
> +
> +static int dvb_dummy_tuner_i2c_probe(struct i2c_client *client,
> +				     const struct i2c_device_id *id)
> +{
> +	int ret = 0;
> +	struct dvb_dummy_tuner_config *config = client->dev.platform_data;
> +	struct dvb_frontend *fe = config->fe;
> +	struct dvb_dummy_tuner_dev *tuner_dev = NULL;
> +
> +	tuner_dev = kzalloc(sizeof(*tuner_dev), GFP_KERNEL);
> +	if (!tuner_dev) {
> +		ret = -ENOMEM;
> +		goto err;

Simplify this by just doing:
	return -ENOMEM;

No need to jump around the function for no actual cleanup.


> +	}
> +
> +	i2c_set_clientdata(client, tuner_dev);
> +	tuner_dev->fe = config->fe;

Normal "pattern" is to set up the variable and after it's all ready,
then save the pointer off.  In other words, reverse these two lines :)

> +
> +	memcpy(&fe->ops.tuner_ops,
> +	       &dvb_dummy_tuner_ops,
> +	       sizeof(struct dvb_tuner_ops));
> +
> +	fe->tuner_priv = client;
> +
> +	return ret;
> +
> +err:
> +	return ret;
> +}
> +
> +static int dvb_dummy_tuner_i2c_remove(struct i2c_client *client)
> +{
> +	struct dvb_dummy_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 dvb_dummy_tuner_i2c_driver = {
> +	.driver = {
> +		.name = "dvb_dummy_tuner",
> +		.suppress_bind_attrs = true,
> +	},
> +	.probe		= dvb_dummy_tuner_i2c_probe,
> +	.remove		= dvb_dummy_tuner_i2c_remove,
> +	.id_table	= dvb_dummy_tuner_i2c_id_table,
> +};
> +module_i2c_driver(dvb_dummy_tuner_i2c_driver);
> +
> +MODULE_DESCRIPTION("DVB Dummy Tuner");
> +MODULE_AUTHOR("Daniel W. S. Almeida");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/media/tuners/dvb_dummy_tuner.h b/drivers/media/tuners/dvb_dummy_tuner.h
> new file mode 100644
> index 000000000000..3569bbc3716e
> --- /dev/null
> +++ b/drivers/media/tuners/dvb_dummy_tuner.h

Why do you need a .h file for a simple driver that does not export
anything to anyone else?

> @@ -0,0 +1,31 @@
> +/* SPDX-License-Identifier: GPL-2.0 */

Not the same license as your .c file?  Odd :(

> +/*
> + * A dummy DVB tuner as part of ongoing work
> + * on a virtual DVB test driver under the 2020 Spring Linux
> + * Kernel Mentorship Program.
> + *
> + * 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.
> + *
> + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>

If you keep this file, same comments as above for the comment block, but
really, you don't need this .h file at all, just drop it.

thanks,

greg k-h

Re: [PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[Daniel W. S. Almeida]

Hi Greg,

I am working on v3. Would you mind clarifying this?


>> + *
>> + * 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.
>> + *
>> + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> Normally this is the first comment line above in this block.
>

Just so we're clear, do you mean this? e.g.:

+ * Copyright (c) 2020 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.
+ *


> Not the same license as your .c file?  Odd :(

Oops! :(


> If you keep this file, same comments as above for the comment block, but
> really, you don't need this .h file at all, just drop it.

OK.


- Daniel

Re: [PATCH v2] media: dvb_dummy_tuner: implement driver skeleton

[Greg KH]

On Mon, Jan 13, 2020 at 03:23:02PM -0300, Daniel W. S. Almeida wrote:
> Hi Greg,
> 
> I am working on v3. Would you mind clarifying this?
> 
> 
> > > + *
> > > + * 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.
> > > + *
> > > + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>
> > Normally this is the first comment line above in this block.
> > 
> 
> Just so we're clear, do you mean this? e.g.:
> 
> + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida@gmail.com>

Yes.