> -----Original Message-----
> From: Ville Syrjälä <[email protected]>
> Sent: Tuesday, February 4, 2020 7:02 PM
> To: Shankar, Uma <[email protected]>
> Cc: [email protected]; [email protected]; Andres
> Rodriguez <[email protected]>
> 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 <[email protected]> On Behalf
> > > Of Ville Syrjala
> > > Sent: Saturday, January 25, 2020 1:32 AM
> > > To: [email protected]
> > > Cc: [email protected]; Andres Rodriguez
> > > <[email protected]>
> > > Subject: [Intel-gfx] [PATCH 6/8] drm/edid: Add a FIXME about DispID
> > > CEA data block revision
> > >
> > > From: Ville Syrjälä <[email protected]>
> > >
> > > 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 <[email protected]>
> >
> > > Cc: Andres Rodriguez <[email protected]>
> > > Signed-off-by: Ville Syrjälä <[email protected]>
> > > ---
> > > 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
> > > [email protected]
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Ville Syrjälä
> Intel
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