[PATCH 3/3] drm/edid: no CEA extension is not an error

[Jean Delvare]

On Mon, 2 Sep 2019 14:46:51 +0300, Ville Syrjälä wrote:
> On Fri, Aug 30, 2019 at 06:16:52PM +0200, Jean Delvare wrote:
> > It is fine for displays without audio functionality to not implement
> > CEA extension in their EDID. Do not return an error in that case,
> > instead return 0 as if there was a CEA extension with no audio or
> > speaker block.
> > 
> > This fixes half of bug fdo#107825:
> > https://bugs.freedesktop.org/show_bug.cgi?id=107825
> > 
> > Signed-off-by: Jean Delvare <jdelvare at suse.de>
> > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > Cc: Maxime Ripard <maxime.ripard at bootlin.com>
> > Cc: Sean Paul <sean at poorly.run>
> > Cc: David Airlie <airlied at linux.ie>
> > Cc: Daniel Vetter <daniel at ffwll.ch>
> > ---
> >  drivers/gpu/drm/drm_edid.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > --- linux-5.2.orig/drivers/gpu/drm/drm_edid.c	2019-08-30 17:57:38.199990995 +0200
> > +++ linux-5.2/drivers/gpu/drm/drm_edid.c	2019-08-30 18:04:36.840333834 +0200
> > @@ -4130,7 +4130,7 @@ int drm_edid_to_sad(struct edid *edid, s
> >  	cea = drm_find_cea_extension(edid);
> >  	if (!cea) {
> >  		DRM_DEBUG_KMS("SAD: no CEA Extension found\n");
> > -		return -ENOENT;
> > +		return 0;
> >  	}  
> 
> Seems reasonable. Maybe the cea_revision<3 branches should alse return 0?

I wasn't sure about that one, as I'm not familiar with this CEA
extension thing.

If revision < 3 means the data is invalid then returning an error is
fine. If on the other hand revision < 3 simply means that the block
types we are looking for were not defined back then yes returning 0
instead would be better.

I'll do whatever developers more familiar with this topic think is
better.

> Either way
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Thanks,
-- 
Jean Delvare
SUSE L3 Support