On Mon, Feb 03, 2020 at 08:15:51PM +0000, Shankar, Uma wrote:
>
>
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Ville Syrjala
> > Sent: Saturday, January 25, 2020 1:32 AM
> > To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx; Andres Rodriguez <andresx7@xxxxxxxxx>
> > Subject: [Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID CEA data block
> > revision
> >
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > 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.
>
> > Cc: Andres Rodriguez <andresx7@xxxxxxxxx>
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> > 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.
> > + */
> > return cea[1];
> > }
> >
> > --
> > 2.24.1
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel
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