linux-kernel - [RFC PATCH][DO NOT COMMIT] media: dvb_frontend: Support concurrent DVB-T/DVB-T2 scan

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Date:   Thu, 11 Jun 2020 13:57:13 +0200
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sean Young <sean@...s.org>, Brad Love <brad@...tdimension.cc>
Cc:     linux-media <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Antti Palosaari <crope@....fi>,
        Jan Pieter van Woerkom <jp@...w.nl>
Subject: [RFC PATCH][DO NOT COMMIT] media: dvb_frontend: Support concurrent
 DVB-T/DVB-T2 scan

Some demodulators (e.g. si2168) are able to scan for DVB-T and DVB-T2
signals concurrently. Use SYS_DVBT_AUTO for this purpose.
---
This is a Request For Comments from media maintainers and users :-)

One issue: suppose DVB Project publishes DVB-T3 in a few years.
Today's demods might handle T/T2, but they won't handle T3, while users
may expect SYS_DVBT_AUTO to mean "all DVB-T standards".

Therefore, perhaps the delsys name should be explicit,
like SYS_DVBT_DVBT2 or SYS_DVBT_1_2.
Then if/when DVB_T3 appears, we can add SYS_DVBT_1_2_3 ???

Or maybe use the FE_CAN_2G_MODULATION and hypothetical FE_CAN_3G_MODULATION

Or maybe, with several standards having a v2 and possibly v3 in the future,
delivery system might move to a bitmask approach? (API issues though)

Reference to related implementation:
https://patchwork.kernel.org/patch/10744999/
---
 drivers/media/dvb-frontends/si2168.c | 2 +-
 include/uapi/linux/dvb/frontend.h    | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/media/dvb-frontends/si2168.c b/drivers/media/dvb-frontends/si2168.c
index 14b93a7d3358..8578b8917955 100644
--- a/drivers/media/dvb-frontends/si2168.c
+++ b/drivers/media/dvb-frontends/si2168.c
@@ -624,7 +624,7 @@ static int si2168_deselect(struct i2c_mux_core *muxc, u32 chan)
 }
 
 static const struct dvb_frontend_ops si2168_ops = {
-	.delsys = {SYS_DVBT, SYS_DVBT2, SYS_DVBC_ANNEX_A},
+	.delsys = {SYS_DVBT, SYS_DVBT2, SYS_DVBT_AUTO, SYS_DVBC_ANNEX_A},
 	.info = {
 		.name = "Silicon Labs Si2168",
 		.frequency_min_hz      =  48 * MHz,
diff --git a/include/uapi/linux/dvb/frontend.h b/include/uapi/linux/dvb/frontend.h
index 4f9b4551c534..3a6348748041 100644
--- a/include/uapi/linux/dvb/frontend.h
+++ b/include/uapi/linux/dvb/frontend.h
@@ -600,6 +600,8 @@ enum fe_rolloff {
  *	Terrestrial TV: DVB-T
  * @SYS_DVBT2:
  *	Terrestrial TV: DVB-T2
+ * @SYS_DVBT_AUTO:
+ *	Terrestrial TV: Autodetect DVB-T gen
  * @SYS_ISDBT:
  *	Terrestrial TV: ISDB-T
  * @SYS_ATSC:
@@ -645,6 +647,7 @@ enum fe_delivery_system {
 	SYS_DVBT2,
 	SYS_TURBO,
 	SYS_DVBC_ANNEX_C,
+	SYS_DVBT_AUTO,
 };
 
 /* backward compatibility definitions for delivery systems */
-- 
2.17.1