[Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID CEA data block revision

[Ville Syrjälä]

On Mon, Feb 03, 2020 at 08:15:51PM +0000, Shankar, Uma wrote:
> 
> 
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville Syrjala
> > Sent: Saturday, January 25, 2020 1:32 AM
> > To: dri-devel at lists.freedesktop.org
> > Cc: intel-gfx at lists.freedesktop.org; Andres Rodriguez <andresx7 at gmail.com>
> > Subject: [Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID CEA data block
> > revision
> > 
> > From: Ville Syrjälä <ville.syrjala at 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.

> 
> > Cc: Andres Rodriguez <andresx7 at gmail.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala at 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.
> > +	 */
> >  	return cea[1];
> >  }
> > 
> > --
> > 2.24.1
> > 
> > _______________________________________________
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> > Intel-gfx at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel