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SubjectRe: [RFC, WIP, v6 03/10] media: vidtv: implement a demodulator driver
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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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