[Linux-kernel-mentees] [RFC 1/3] media: dvb_dummy_tuner: implement driver skeleton

Mauro Carvalho Chehab mchehab+huawei at kernel.org
Wed Mar 18 08:17:48 UTC 2020


Em Wed, 18 Mar 2020 03:00:16 -0300
"Daniel W. S. Almeida" <dwlsalmeida at gmail.com> escreveu:

> From: "Daniel W. S. Almeida" <dwlsalmeida at 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 at gmail.com>
> ---
>  drivers/media/tuners/Kconfig           |   9 +
>  drivers/media/tuners/Makefile          |   1 +
>  drivers/media/tuners/dvb_dummy_tuner.c | 421 +++++++++++++++++++++++++
>  3 files changed, 431 insertions(+)
>  create mode 100644 drivers/media/tuners/dvb_dummy_tuner.c
> 
> diff --git a/drivers/media/tuners/Kconfig b/drivers/media/tuners/Kconfig
> index e104bb7766e1..8ad54339ceee 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 DVB Media Tuner"
> +	depends on MEDIA_SUPPORT && I2C
> +	help
> +	  Dummy DVB media tuner driver
> +	  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..1408a8c84be2
> --- /dev/null
> +++ b/drivers/media/tuners/dvb_dummy_tuner.c
> @@ -0,0 +1,421 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2020 Daniel W. S. Almeida <dwlsalmeida at 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.
> + *
> + */
> +
> +#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>
> +
> +struct dvb_dummy_tuner_config {
> +	struct dvb_frontend *fe;
> +	u32 mock_power_up_delay_msec;
> +	u32 mock_tune_delay_msec;
> +	u32 mock_sleep_delay_msec;
> +	u32 mock_resume_delay_msec;
> +	u32 dummy_valid_dvb_t_frequencies[8];
> +	u32 dummy_valid_dvb_c_frequencies[8];
> +	u32 dummy_valid_dvb_s_frequencies[8];
> +	u8  max_frequency_shift_hz;
> +};
> +
> +struct dvb_dummy_tuner_cnr_to_qual_s {
> +	/* attempt to use the same values as libdvbv5 */
> +	u32 modulation;
> +	u32 fec;
> +	u32 cnr_ok, cnr_good;
> +};
> +
> +struct dvb_dummy_tuner_cnr_to_qual_s dvb_c_cnr_2_qual[] = {
> +	/* from libdvbv5 source code */
> +	{ QAM_256, FEC_NONE,  34., 38.},
> +	{ QAM_64,  FEC_NONE,  30., 34.},

Instead of using float point, you should multiply those by some value,
like 1000. So, 34.0 dB would become 34000. Btw, that's the way the DVBv5
API expects it: as mili-dB. See FE_SCALE_DECIBEL at:

	https://linuxtv.org/downloads/v4l-dvb-apis-new/uapi/dvb/frontend-stat-properties.html#dtv-stat-cnr

> +};
> +
> +struct dvb_dummy_tuner_cnr_to_qual_s dvb_s_cnr_2_qual[] = {
> +	/* from libdvbv5 source code */
> +	{ QPSK, FEC_1_2,  7., 10.},
> +
> +	{ QPSK, FEC_2_3,  9., 12.},
> +	{ QPSK, FEC_3_4, 10., 13.},
> +	{ QPSK, FEC_5_6, 11., 14.},
> +
> +	{ QPSK, FEC_7_8, 12., 15.},
> +};
> +
> +struct dvb_dummy_tuner_cnr_to_qual_s dvb_s2_cnr_2_qual[] = {
> +	/* from libdvbv5 source code */
> +	{ QPSK,  FEC_1_2,   9.,  12.},
> +	{ QPSK,  FEC_2_3,  11.,  14.},
> +	{ QPSK,  FEC_3_4,  12.,  15.},
> +	{ QPSK,  FEC_5_6,  12.,  15.},
> +	{ QPSK,  FEC_8_9,  13.,  16.},
> +	{ QPSK,  FEC_9_10, 13.5, 16.5},
> +	{ PSK_8, FEC_2_3,  14.5, 17.5},
> +	{ PSK_8, FEC_3_4,  16.,  19.},
> +	{ PSK_8, FEC_5_6,  17.5, 20.5},
> +	{ PSK_8, FEC_8_9,  19.,  22.},
> +};
> +
> +static struct dvb_dummy_tuner_cnr_to_qual_s dvb_t_cnr_2_qual[] = {
> +	/* from libdvbv5 source code */
> +	{   QPSK, FEC_1_2,  4.1,  5.9},
> +	{   QPSK, FEC_2_3,  6.1,  9.6},
> +	{   QPSK, FEC_3_4,  7.2, 12.4},
> +	{   QPSK, FEC_5_6,  8.5, 15.6},
> +	{   QPSK, FEC_7_8,  9.2, 17.5},
> +
> +	{ QAM_16, FEC_1_2,  9.8, 11.8},
> +	{ QAM_16, FEC_2_3, 12.1, 15.3},
> +	{ QAM_16, FEC_3_4, 13.4, 18.1},
> +	{ QAM_16, FEC_5_6, 14.8, 21.3},
> +	{ QAM_16, FEC_7_8, 15.7, 23.6},
> +
> +	{ QAM_64, FEC_1_2, 14.0, 16.0},
> +	{ QAM_64, FEC_2_3, 19.9, 25.4},
> +	{ QAM_64, FEC_3_4, 24.9, 27.9},
> +	{ QAM_64, FEC_5_6, 21.3, 23.3},
> +	{ QAM_64, FEC_7_8, 22.0, 24.0},
> +};
> +
> +enum dvb_dummy_tuner_lock_status {
> +	STATUS_NO_LOCK = 0,
> +	STATUS_LOCKED = TUNER_STATUS_LOCKED,
> +};
> +
> +enum dvb_dummy_tuner_power_status {
> +	STATUS_UNKNOWN,
> +	STATUS_ASLEEP,
> +	STATUS_ACTIVE
> +};
> +
> +enum dvb_dummy_tuner_frequency_shift_status {
> +	EXACT_MATCH,
> +	CLOSE_MATCH,
> +	TOO_FAR_OFF
> +};
> +
> +struct dvb_dummy_tuner_hardware_state {
> +	enum dvb_dummy_tuner_power_status power_status;
> +	enum dvb_dummy_tuner_lock_status lock_status;
> +	u32 if_frequency;
> +	u32 tuned_frequency;
> +	u32 bandwidth;
> +};
> +
> +struct dvb_dummy_tuner_dev {
> +	struct dvb_frontend *fe;
> +	struct dvb_dummy_tuner_hardware_state hw_state;
> +	struct dvb_dummy_tuner_config config;
> +};
> +
> +static struct dvb_dummy_tuner_dev*
> +dvb_dummy_tuner_get_dev(struct dvb_frontend *fe)
> +{
> +	struct i2c_client *client = fe->tuner_priv;
> +
> +	return (struct dvb_dummy_tuner_dev *)i2c_get_clientdata(client);
> +}
> +
> +static bool dvb_dummy_tuner_check_frequency_shift(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
> +	struct dvb_dummy_tuner_config config = tuner_dev->config;
> +	u32 *valid_frequencies = NULL;
> +	u32 array_sz = 0;
> +	u32 i;
> +
> +	switch (c->delivery_system) {
> +	case SYS_DVBT:
> +	case SYS_DVBT2:
> +		valid_frequencies =
> +			config.dummy_valid_dvb_t_frequencies;

Please avoid splitting assignments like that on multiple lines.

Btw, I would just do a s/frequencies/freqs/. So, that would be:

		valid_freqs = config.dummy_valid_dvb_t_freqs;

> +		array_sz = ARRAY_SIZE(config.dummy_valid_dvb_t_frequencies);
> +		break;
> +	case SYS_DVBS:
> +	case SYS_DVBS2:
> +		valid_frequencies =
> +			config.dummy_valid_dvb_s_frequencies;
> +		array_sz = ARRAY_SIZE(config.dummy_valid_dvb_s_frequencies);
> +		break;
> +	case SYS_DVBC_ANNEX_A:
> +		valid_frequencies =
> +			config.dummy_valid_dvb_c_frequencies;
> +		array_sz = ARRAY_SIZE(config.dummy_valid_dvb_c_frequencies);
> +		break;
> +
> +	default:
> +		pr_warn("%s: unsupported delivery system: %u\n",
> +			__func__,
> +			c->delivery_system);
> +		break;
> +	}
> +
> +	for (i = 0; i < array_sz; i++) {
> +		if (c->frequency == valid_frequencies[i])
> +			return EXACT_MATCH;

I would, instead, return 0 here.

> +		else if (c->frequency >= ) -
> +			 config.max_frequency_shift_hz &&
> +			 c->frequency <= valid_frequencies[i] +
> +			 config.max_frequency_shift_hz)
> +			return CLOSE_MATCH;

I would, instead, do:

	return abs((c->frequency - valid_frequencies[i]) * 100 / config.max_frequency_shift_hz);

This will provide a value from 0 to 100 that would indicate how far is the
tuned frequency from the right one.

> +	}
> +
> +	return TOO_FAR_OFF;

I would return -1.

> +}
> +
> +static int
> +dvb_dummy_tuner_get_signal_strength(struct dvb_frontend *fe, u16 *strength)
> +{
> +	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
> +	struct dvb_dummy_tuner_cnr_to_qual_s *cnr2qual = NULL;
> +	u32 array_size = 0;
> +	enum dvb_dummy_tuner_frequency_shift_status shift_status;
> +	u32 i;
> +
> +	shift_status = dvb_dummy_tuner_check_frequency_shift(fe);
> +
> +	switch (c->delivery_system) {
> +	case SYS_DVBT:
> +	case SYS_DVBT2:
> +		cnr2qual = dvb_t_cnr_2_qual;
> +		array_size = ARRAY_SIZE(dvb_t_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS:
> +		cnr2qual = dvb_s_cnr_2_qual;
> +		array_size = ARRAY_SIZE(dvb_s_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBS2:
> +		cnr2qual = dvb_s2_cnr_2_qual;
> +		array_size = ARRAY_SIZE(dvb_s2_cnr_2_qual);
> +		break;
> +
> +	case SYS_DVBC_ANNEX_A:
> +		cnr2qual = dvb_c_cnr_2_qual;
> +		array_size = ARRAY_SIZE(dvb_c_cnr_2_qual);
> +		break;
> +
> +	default:
> +		pr_warn("%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) {
> +			*strength = (shift_status == EXACT_MATCH) ?
> +				    cnr2qual[i].cnr_good :
> +				    (shift_status == CLOSE_MATCH) ?
> +				    cnr2qual[i].cnr_ok :
> +				    cnr2qual[i].cnr_ok -
> +				    (cnr2qual[i].cnr_good - cnr2qual[i].cnr_ok);
> +			return 0;
> +		}
> +
> +	}
> +
> +	/* default to some random values if we can't match against the table */
> +	*strength = (shift_status == EXACT_MATCH) ? 34 : 10;

Perhaps you could, instead, use the frequency shift to calculate the
strength between 34 and 10. 

So, assuming that you take my suggestion of returning a value from 0 to 100,
and such value is stored at a "shift" var, you could do:

	*strength = 34 - 24 * shift / 100;

(ok, a linear interpolation is not what would happen on a real case, but
as the goal of a virtual driver is to validate if userspace is doing the 
right thing, this works just fine).

> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_init(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +	struct dvb_dummy_tuner_config config = tuner_dev->config;
> +
> +	msleep_interruptible(config.mock_power_up_delay_msec);
> +
> +	tuner_dev->hw_state.power_status = STATUS_ACTIVE;
> +	tuner_dev->hw_state.if_frequency = 5000;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_sleep(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +	struct dvb_dummy_tuner_config config = tuner_dev->config;
> +
> +	msleep_interruptible(config.mock_sleep_delay_msec);
> +	tuner_dev->hw_state.power_status = STATUS_ASLEEP;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_suspend(struct dvb_frontend *fe)
> +{
> +	return dvb_dummy_tuner_sleep(fe);
> +}
> +
> +static int dvb_dummy_tuner_resume(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +	struct dvb_dummy_tuner_config config = tuner_dev->config;
> +
> +	msleep_interruptible(config.mock_resume_delay_msec);
> +	tuner_dev->hw_state.power_status = STATUS_ACTIVE;
> +
> +	return 0;
> +}

For suspend/resume, I would not do any msleep(). Just set the status.

> +
> +static int dvb_dummy_tuner_set_params(struct dvb_frontend *fe)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +	struct dvb_dummy_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;
> +
> +	msleep_interruptible(config.mock_tune_delay_msec);
> +
> +	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 = STATUS_NO_LOCK;
> +		return -EINVAL;
> +	}

You can move the msleep() to be after checking the parameters.
This is what happens on other drivers.

> +
> +	tuner_dev->hw_state.tuned_frequency = c->frequency;
> +	tuner_dev->hw_state.bandwidth = c->bandwidth_hz;
> +	tuner_dev->hw_state.lock_status = STATUS_LOCKED;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_set_config(struct dvb_frontend *fe,
> +				      void *priv_cfg)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +
> +	WARN_ON(sizeof(tuner_dev->config) != sizeof(*priv_cfg));
> +	memcpy(&tuner_dev->config, priv_cfg, sizeof(*priv_cfg));

Huh? sizeof(void *priv_config) seems plain wrong to me. The above
shold be, instead:

	memcpy(&tuner_dev->config, priv_cfg, sizeof(tuner_dev->config));

but you should ensure that the caller driver will be filling it
properly there.

> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_frequency(struct dvb_frontend *fe,
> +					 u32 *frequency)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +
> +	*frequency = tuner_dev->hw_state.tuned_frequency;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_bandwidth(struct dvb_frontend *fe,
> +					 u32 *bandwidth)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +
> +	*bandwidth = tuner_dev->hw_state.bandwidth;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_if_frequency(struct dvb_frontend *fe,
> +					    u32 *frequency)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +
> +	*frequency = tuner_dev->hw_state.if_frequency;
> +
> +	return 0;
> +}
> +
> +static int dvb_dummy_tuner_get_status(struct dvb_frontend *fe, u32 *status)
> +{
> +	struct dvb_dummy_tuner_dev *tuner_dev = dvb_dummy_tuner_get_dev(fe);
> +
> +	*status = tuner_dev->hw_state.lock_status;
> +
> +	return 0;
> +}
> +
> +static const struct dvb_tuner_ops dvb_dummy_tuner_ops = {
> +	.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,
> +	.get_rf_strength = dvb_dummy_tuner_get_signal_strength
> +};
> +
> +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)
> +{
> +	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)
> +		return -ENOMEM;
> +
> +	tuner_dev->fe = config->fe;
> +	i2c_set_clientdata(client, tuner_dev);
> +
> +	memcpy(&fe->ops.tuner_ops,
> +	       &dvb_dummy_tuner_ops,
> +	       sizeof(struct dvb_tuner_ops));
> +
> +	fe->tuner_priv = client;
> +
> +	return 0;
> +}
> +
> +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");



Thanks,
Mauro


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