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

[Ville Syrjälä]

On Mon, Sep 02, 2019 at 01:55:21PM +0200, Jean Delvare wrote:
> 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.

That is indeed the case. A quick read through the code showed that
we're not 100% consistent in checing for that though. I just send
a few patches to fix that up.

-- 
Ville Syrjälä
Intel