text: // 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)
  {
  	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
  	struct device *dev = fe->dvb->device;
  	struct dtv_frontend_properties *c;
  	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:
  		dev_warn_ratelimited(dev,
  				     "%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_clean_stats(struct dvb_frontend *fe)
  {
  	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
  
  	/* Fill the length of each status counter */
  
  	/* Signal is always available */
  	c->strength.len = 1;
  	c->strength.stat[0].scale = FE_SCALE_DECIBEL;
  	c->strength.stat[0].svalue = 0;
  
  	/* Usually available only after Viterbi lock */
  	c->cnr.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->cnr.stat[0].svalue = 0;
  	c->cnr.len = 1;
  
  	/* Those depends on full lock */
  	c->pre_bit_error.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->pre_bit_error.stat[0].uvalue = 0;
  	c->pre_bit_error.len = 1;
  	c->pre_bit_count.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->pre_bit_count.stat[0].uvalue = 0;
  	c->pre_bit_count.len = 1;
  	c->post_bit_error.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->post_bit_error.stat[0].uvalue = 0;
  	c->post_bit_error.len = 1;
  	c->post_bit_count.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->post_bit_count.stat[0].uvalue = 0;
  	c->post_bit_count.len = 1;
  	c->block_error.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->block_error.stat[0].uvalue = 0;
  	c->block_error.len = 1;
  	c->block_count.stat[0].scale = FE_SCALE_NOT_AVAILABLE;
  	c->block_count.stat[0].uvalue = 0;
  	c->block_count.len = 1;
  }
  
  static void vidtv_demod_update_stats(struct dvb_frontend *fe)
  {
  	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
  	struct vidtv_demod_state *state = fe->demodulator_priv;
  	u32 scale;
  
  	if (state->status & FE_HAS_LOCK) {
  		scale = FE_SCALE_COUNTER;
  		c->cnr.stat[0].scale = FE_SCALE_DECIBEL;
  	} else {
  		scale = FE_SCALE_NOT_AVAILABLE;
  		c->cnr.stat[0].scale = scale;
  	}
  
  	c->pre_bit_error.stat[0].scale = scale;
  	c->pre_bit_count.stat[0].scale = scale;
  	c->post_bit_error.stat[0].scale = scale;
  	c->post_bit_count.stat[0].scale = scale;
  	c->block_error.stat[0].scale = scale;
  	c->block_count.stat[0].scale = scale;
  
  	/*
  	 * Add a 0.5% of randomness at the signal strength and CNR,
  	 * and make them different, as we want to have something closer
  	 * to a real case scenario.
  	 *
  	 * Also, usually, signal strength is a negative number in dBm.
  	 */
  	c->strength.stat[0].svalue = state->tuner_cnr;
  	c->strength.stat[0].svalue -= prandom_u32_max(state->tuner_cnr / 50);
  	c->strength.stat[0].svalue -= 68000; /* Adjust to a better range */
  
  	c->cnr.stat[0].svalue = state->tuner_cnr;
  	c->cnr.stat[0].svalue -= prandom_u32_max(state->tuner_cnr / 50);
  }
  
  static int vidtv_demod_read_status(struct dvb_frontend *fe,
  				   enum fe_status *status)
  {
  	struct vidtv_demod_state *state = fe->demodulator_priv;
  	const struct vidtv_demod_cnr_to_qual_s *cnr2qual = NULL;
  	struct vidtv_demod_config *config = &state->config;
  	u16 snr = 0;
  
  	/* Simulate random lost of signal due to a bad-tuned channel */
  	cnr2qual = vidtv_match_cnr_s(&state->frontend);
  
  	if (cnr2qual && state->tuner_cnr < cnr2qual->cnr_good &&
  	    state->frontend.ops.tuner_ops.get_rf_strength) {
  		state->frontend.ops.tuner_ops.get_rf_strength(&state->frontend,
  							      &snr);
  
  		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;
  		}
  	}
  
  	vidtv_demod_update_stats(&state->frontend);
  
  	*status = state->status;
  
  	return 0;
  }
  
  static int vidtv_demod_read_signal_strength(struct dvb_frontend *fe,
  					    u16 *strength)
  {
  	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
  
  	*strength = c->strength.stat[0].uvalue;
  
  	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;
  	u32 tuner_status = 0;
  	int ret;
  
  	if (!fe->ops.tuner_ops.set_params)
  		return 0;
  
  	fe->ops.tuner_ops.set_params(fe);
  
  	/* store the CNR returned by the tuner */
  	ret = fe->ops.tuner_ops.get_rf_strength(fe, &state->tuner_cnr);
  	if (ret < 0)
  		return ret;
  
  	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;
  
  	vidtv_demod_update_stats(fe);
  
  	if (fe->ops.i2c_gate_ctrl)
  		fe->ops.i2c_gate_ctrl(fe, 0);
  
  	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;
  }
  
  /*
   * 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_send_diseqc_msg(struct dvb_frontend *fe,
  				 struct dvb_diseqc_master_cmd *cmd)
  {
  	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_diseqc_send_burst(struct dvb_frontend *fe,
  				   enum fe_sec_mini_cmd burst)
  {
  	return 0;
  }
  
  static void vidtv_demod_release(struct dvb_frontend *fe)
  {
  	struct vidtv_demod_state *state = fe->demodulator_priv;
  
  	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,
  
  	.set_frontend = vidtv_demod_set_frontend,
  	.get_frontend = vidtv_demod_get_frontend,
  
  	.read_status          = vidtv_demod_read_status,
  	.read_signal_strength = vidtv_demod_read_signal_strength,
  
  	/* For DVB-S/S2 */
  	.set_voltage		= vidtv_demod_set_voltage,
  	.set_tone		= vidtv_demod_set_tone,
  	.diseqc_send_master_cmd	= vidtv_send_diseqc_msg,
  	.diseqc_send_burst	= vidtv_diseqc_send_burst,
  
  };
  
  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_tuner_config *config = client->dev.platform_data;
  	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));
  
  	memcpy(&state->config, config, sizeof(state->config));
  
  	state->frontend.demodulator_priv = state;
  	i2c_set_clientdata(client, state);
  
  	vidtv_clean_stats(&state->frontend);
  
  	return 0;
  }
  
  static int vidtv_demod_i2c_remove(struct i2c_client *client)
  {
  	struct vidtv_demod_state *state = i2c_get_clientdata(client);
  
  	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");
  