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media: vidtv: implement a demodulator driver

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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>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Daniel W. S. Almeida 2020-08-21 14:58:46 +02:00 committed by Mauro Carvalho Chehab
parent 24fb190e92
commit f5ffc3b6ed
3 changed files with 515 additions and 1 deletions
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3
drivers/media/test-drivers/vidtv/Makefile
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# 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

440
drivers/media/test-drivers/vidtv/vidtv_demod.c Normal file
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// 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.
*
* Copyright (C) 2020 Daniel W. S. Almeida
* 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"
#define POLL_THRD_TIME 2000 /* 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)
{
struct dtv_frontend_properties *c;
const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
u32 array_size = 0;
u32 i;
c = &fe->dtv_property_cache;
switch (c->delivery_system) {
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_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,
},
.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[] = {
{"dvb_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 = "dvb_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");

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drivers/media/test-drivers/vidtv/vidtv_demod.h Normal file
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/* 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.
*
* Copyright (C) 2020 Daniel W. S. Almeida
* 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 - Map CNR values to a given combination of
* modulation and fec_inner
* @modulation: see enum fe_modulation
* @fec: see enum fe_fec_rate
*
* This struct matches values for 'good' and 'ok' CNRs given the combination
* of modulation and fec_inner in use. We might simulate some noise if the
* signal quality is not too good.
*
* The values were taken from libdvbv5.
*/
struct vidtv_demod_cnr_to_qual_s {
u32 modulation;
u32 fec;
u32 cnr_ok;
u32 cnr_good;
};
/**
* struct vidtv_demod_config - Configuration used to init the demod
* @drop_tslock_prob_on_low_snr: probability of losing the lock due to low snr
* @recover_tslock_prob_on_good_snr: probability of recovering when the signal
* improves
*
* The configuration used to init the demodulator module, usually filled
* by a bridge driver. For vidtv, this is filled by vidtv_bridge before the
* demodulator module is probed.
*/
struct vidtv_demod_config {
u8 drop_tslock_prob_on_low_snr;
u8 recover_tslock_prob_on_good_snr;
};
/**
* struct vidtv_demod_state - The demodulator state
* @frontend: The frontend structure allocated by the demod.
* @config: The config used to init the demod.
* @poll_snr: The task responsible for periodically checking the simulated
* signal quality, eventually dropping or reacquiring the TS lock.
* @status: the demod status.
* @cold_start: Whether the demod has not been init yet.
* @poll_snr_thread_running: Whether the task responsible for periodically
* checking the simulated signal quality is running.
* @poll_snr_thread_restart: Whether we should restart the poll_snr task.
*/
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