-----Original Message----- From: Ville Syrjälä ville.syrjala@linux.intel.com Sent: Tuesday, February 4, 2020 7:02 PM To: Shankar, Uma uma.shankar@intel.com Cc: dri-devel@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; Andres Rodriguez andresx7@gmail.com Subject: Re: [Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID CEA data block revision
On Mon, Feb 03, 2020 at 08:15:51PM +0000, Shankar, Uma wrote:
-----Original Message----- From: Intel-gfx intel-gfx-bounces@lists.freedesktop.org On Behalf Of Ville Syrjala Sent: Saturday, January 25, 2020 1:32 AM To: dri-devel@lists.freedesktop.org Cc: intel-gfx@lists.freedesktop.org; Andres Rodriguez andresx7@gmail.com Subject: [Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID CEA data block revision
From: Ville Syrjälä ville.syrjala@linux.intel.com
I don't understand what the DispID CEA data block revision means. The spec doesn't say. I guess some DispID must have a value of >= 3 in there or else we generally wouldn't even parse the CEA data blocks. Or does all this code actually not do anything?
This signifies the CTA extension revision (byte 1 of the block). As per the spec, seems like Version 1 is legacy and 2 is deprecated. So version >=3 is
checked here.
Refer section 7.3 of CTA-861-G
The confusion is about the revision field in the DispID CTA block, not in the CTA extension block.
Oh ok, got the ambiguity here. Not sure if we actually get >3 here as value for the block revision, totally unclear from spec, default being 0. Good to have this comment till we get some clarity on its significance. Thanks for the clarification.
Reviewed-by: Uma Shankar uma.shankar@intel.com
Cc: Andres Rodriguez andresx7@gmail.com Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com
drivers/gpu/drm/drm_edid.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 0369a54e3d32..fd9b724067a7 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -3977,6 +3977,13 @@ cea_db_tag(const u8 *db) static int cea_revision(const u8 *cea) {
- /*
* FIXME is this correct for the DispID variant?* The DispID spec doesn't really specify whether* this is the revision of the CEA extension or* the DispID CEA data block. And the only value* given as an example is 0.*/}
-- 2.24.1
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