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From: "Krzysztof Hałasa" <>
To: Hans Verkuil <>
Cc: Tim Harvey <>,
	Mauro Carvalho Chehab <>,, lkml <>
Subject: Re: [PATCH REPOST] TDA1997x: replace video detection routine
Date: Thu, 22 Jul 2021 08:27:27 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <> (Hans Verkuil's message of "Wed, 21 Jul 2021 09:12:08 +0200")


I have a problem with matching H/V sync polarities. It appears the
standard modes use different polarity settings, and HDMI doesn't have
separate sync lines, it uses in-band signaling. I don't know what
polarity should I set for the v4l2_find_dv_timings_cap() ->
v4l2_match_dv_timings() to succeed.

1. I can try all 4 combinations (+/+, +/-, -/+, -/-) and see if there is
a match. Seems weird to me.

2. I can add a flag to v4l2_find_dv_timings_cap() ->
v4l2_match_dv_timings() which asks for the polarities to be ignored.

3. I could add
 #define V4L2_DV_VSYNC_POS_POL   0x00000001
 #define V4L2_DV_HSYNC_POS_POL   0x00000002
+#define V4L2_DV_VSYNC_ANY_POL   0x00000004
+#define V4L2_DV_HSYNC_ANY_POL   0x00000008

and v4l2_match_dv_timings() would skip comparing them. A bit hacky.

4. I could also add
 #define V4L2_DV_VSYNC_POS_POL   0x00000001
 #define V4L2_DV_HSYNC_POS_POL   0x00000002
+#define V4L2_DV_VSYNC_NEG_POL   0x00000004
+#define V4L2_DV_HSYNC_NEG_POL   0x00000008

and, likewise, v4l2_match_dv_timings() would know what to do. This is
IMHO cleaner but requires much more changes in other code (like

Any other idea?
Perhaps I should do "2"?

Krzysztof "Chris" Hałasa

Sieć Badawcza Łukasiewicz
Przemysłowy Instytut Automatyki i Pomiarów PIAP
Al. Jerozolimskie 202, 02-486 Warszawa

  parent reply	other threads:[~2021-07-22  6:27 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19  9:30 Krzysztof Hałasa
2021-07-21  7:12 ` Hans Verkuil
2021-07-21  7:56   ` Krzysztof Hałasa
2021-07-21 10:04     ` Hans Verkuil
2021-07-22  6:27   ` Krzysztof Hałasa [this message]
2021-07-22  6:43     ` Krzysztof Hałasa
2021-07-23  8:24       ` Hans Verkuil
2021-07-23  8:49     ` Hans Verkuil
2021-07-23 11:57       ` Krzysztof Hałasa

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