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Subject: Re: [RFC, WIP, v6 02/10] media: vidtv: implement a tuner driver
To:     "Daniel W. S. Almeida" <dwlsalmeida@gmail.com>,
        mchehab+huawei@kernel.org, sean@mess.org,
        kstewart@linuxfoundation.org, allison@lohutok.net,
        tglx@linutronix.de
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        linux-kernel-mentees@lists.linuxfoundation.org,
        linux-kernel@vger.kernel.org, skhan@linuxfoundation.org
References: <20200520070334.1778751-1-dwlsalmeida@gmail.com>
 <20200520070334.1778751-3-dwlsalmeida@gmail.com>
From:   Shuah Khan <skhan@linuxfoundation.org>
Message-ID: <deb6b49a-5f50-1d40-6577-84fe787150ec@linuxfoundation.org>
Date:   Thu, 28 May 2020 17:26:41 -0600
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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