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libdvbv5: dvb-scan: fix DVB-S2 checks for DVB-S tuning

Message ID 20211214122523.569011-1-mchehab+huawei@kernel.org (mailing list archive)
State New, archived
Headers show
Series libdvbv5: dvb-scan: fix DVB-S2 checks for DVB-S tuning | expand

Commit Message

Mauro Carvalho Chehab Dec. 14, 2021, 12:25 p.m. UTC 
When DVB-S2 tunning is requested, the tuner may report both
DVB-S and DVB-S2 frequencies. There's a logic that tries to
discover if the channel is either S or S2, but such logic is
incomplete, causing problems.

Fix it, doing a complete check for DVB-S compatible parameters.

Reported-by: Stefan Seyfried <stefan.seyfried@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 lib/libdvbv5/dvb-scan.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)
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Patch

diff --git a/lib/libdvbv5/dvb-scan.c b/lib/libdvbv5/dvb-scan.c
index 5c8aca96df33..5bbeec1fa4fc 100644
--- a/lib/libdvbv5/dvb-scan.c
+++ b/lib/libdvbv5/dvb-scan.c
@@ -1118,9 +1118,33 @@  static void add_update_nit_dvbs(struct dvb_table_nit *nit,
 			     dvbs_dvbc_dvbs_freq_inner[d->fec]);
 	dvb_store_entry_prop(new, DTV_ROLLOFF,
 			     dvbs_rolloff[d->roll_off]);
-	if (d->roll_off != 0)
-		dvb_store_entry_prop(new, DTV_DELIVERY_SYSTEM,
-				     SYS_DVBS2);
+
+	/*
+	 * Check if the returned parameters are really DVB-S or not
+	 *
+	 * DVB-S supports only 0.35 roll-off, with QPSK and
+	 * Red-Solomon FEC 1/2, 2/3, 3/4, 5/6, 7/8. If anythign else is
+	 * reported, then it is DVB-S2.
+	 */
+
+	if ((d->roll_off != 0 && d->roll_off != ROLLOFF_35) ||
+	    (d->modulation_system != 0 && d->modulation_system != QPSK)) {
+		dvb_store_entry_prop(new, DTV_DELIVERY_SYSTEM, SYS_DVBS2);
+		return;
+	}
+
+	switch (d->fec) {
+	case FEC_NONE:
+	case FEC_AUTO:
+	case FEC_1_2:
+	case FEC_2_3:
+	case FEC_3_4:
+	case FEC_5_6:
+	case FEC_7_8:
+		return;
+	default:
+		dvb_store_entry_prop(new, DTV_DELIVERY_SYSTEM, SYS_DVBS2);
+	}
 }
 
 static void add_update_nit_isdbs(struct dvb_table_nit *nit,