[Linux-kernel-mentees] [PATCH] media: dvb_dummy_fe.c: lose TS lock on bad snr
Daniel W. S. Almeida
dwlsalmeida at gmail.com
Mon Feb 10 15:45:55 UTC 2020
From: "Daniel W. S. Almeida" <dwlsalmeida at gmail.com>
Periodically check the signal quality and eventually lose the lock if
the quality is sub-par. A fake tuner can return a bad quality signal to
the demod if the frequency is too far off from a valid frequency.
Signed-off-by: Daniel W. S. Almeida <dwlsalmeida at gmail.com>
---
drivers/media/dvb-frontends/dvb_dummy_fe.c | 149 ++++++++++++++++++++-
1 file changed, 144 insertions(+), 5 deletions(-)
diff --git a/drivers/media/dvb-frontends/dvb_dummy_fe.c b/drivers/media/dvb-frontends/dvb_dummy_fe.c
index 9ff1ebaa5e04..726c964a523d 100644
--- a/drivers/media/dvb-frontends/dvb_dummy_fe.c
+++ b/drivers/media/dvb-frontends/dvb_dummy_fe.c
@@ -9,24 +9,155 @@
#include <linux/init.h>
#include <linux/string.h>
#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/random.h>
#include <media/dvb_frontend.h>
#include "dvb_dummy_fe.h"
+struct dvb_dummy_fe_cnr_to_qual_s {
+ /* attempt to use the same values as libdvbv5 */
+ u32 modulation;
+ u32 fec;
+ u32 cnr_ok, cnr_good;
+};
+
+struct dvb_dummy_fe_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.},
+};
+
+struct dvb_dummy_fe_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_fe_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_fe_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},
+};
+
+struct dvb_dummy_fe_config {
+ /* probability of losing the lock due to low snr */
+ u8 drop_tslock_probability_on_low_snr;
+};
+
struct dvb_dummy_fe_state {
struct dvb_frontend frontend;
+ struct dvb_dummy_fe_config config;
+ struct delayed_work poll_snr;
+ enum fe_status status;
};
+void poll_snr_handler(struct work_struct *work)
+{
+ /* periodically check the signal quality and eventually
+ * lose the TS lock if it dips too low
+ */
+ struct dvb_dummy_fe_state *state =
+ container_of(work, struct dvb_dummy_fe_state, poll_snr.work);
+ struct dtv_frontend_properties *c = &state->frontend.dtv_property_cache;
+ struct dvb_dummy_fe_cnr_to_qual_s *cnr2qual = NULL;
+ struct dvb_dummy_fe_config *config = &state->config;
+ u32 array_size = 0;
+ u16 snr = 0;
+ u32 i;
+
+ if (!state->frontend.ops.tuner_ops.get_rf_strength)
+ return;
+
+ state->frontend.ops.tuner_ops.get_rf_strength(&state->frontend, &snr);
+
+ 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);
+ break;
+ }
+
+ for (i = 0; i <= array_size; i++) {
+ if (cnr2qual[i].modulation == c->modulation &&
+ cnr2qual[i].fec == c->fec_inner) {
+
+ if (snr < cnr2qual[i].cnr_ok) {
+ /* eventually lose the TS lock */
+ if (prandom_u32_max(100) <
+ config->drop_tslock_probability_on_low_snr)
+ state->status = 0;
+ }
+ }
+ }
+
+ schedule_delayed_work(&(state->poll_snr), msecs_to_jiffies(2000));
+}
static int dvb_dummy_fe_read_status(struct dvb_frontend *fe,
enum fe_status *status)
{
- *status = FE_HAS_SIGNAL
- | FE_HAS_CARRIER
- | FE_HAS_VITERBI
- | FE_HAS_SYNC
- | FE_HAS_LOCK;
+
+ struct dvb_dummy_fe_state *state = fe->demodulator_priv;
+
+ *status = state->status;
return 0;
}
@@ -80,11 +211,18 @@ static int dvb_dummy_fe_set_frontend(struct dvb_frontend *fe)
static int dvb_dummy_fe_sleep(struct dvb_frontend *fe)
{
+ struct dvb_dummy_fe_state *state = fe->demodulator_priv;
+
+ cancel_delayed_work_sync(&(state->poll_snr));
return 0;
}
static int dvb_dummy_fe_init(struct dvb_frontend *fe)
{
+ struct dvb_dummy_fe_state *state = fe->demodulator_priv;
+
+ INIT_DELAYED_WORK(&(state->poll_snr), &poll_snr_handler);
+ schedule_delayed_work(&(state->poll_snr), msecs_to_jiffies(2000));
return 0;
}
@@ -104,6 +242,7 @@ static void dvb_dummy_fe_release(struct dvb_frontend *fe)
{
struct dvb_dummy_fe_state *state = fe->demodulator_priv;
+ cancel_delayed_work_sync(&(state->poll_snr));
kfree(state);
}
--
2.25.0
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