[PATCH 1/3] drm: Tune up error message during format->bpp/cpp conversion

[Daniel Vetter]

On Thu, May 12, 2016 at 05:00:06PM +0300, Imre Deak wrote:
> On Thu, 2016-05-12 at 16:52 +0300, Ville Syrjälä wrote:
> > On Thu, May 12, 2016 at 04:43:05PM +0300, Imre Deak wrote:
> > > On Thu, 2016-05-12 at 16:10 +0300, Ville Syrjälä wrote:
> > > > On Thu, May 12, 2016 at 04:00:38PM +0300, Imre Deak wrote:
> > > > > Returning a 0 bpp/cpp value from these functions isn't ever
> > > > > valid.
> > > > > In
> > > > > many cases it can also lead to a div-by-zero possibly at some
> > > > > later
> > > > > point in time, so make sure we catch such errors as soon as
> > > > > possible via
> > > > > louder error reporting.
> > > > > 
> > > > > CC: Dave Airlie <airlied at redhat.com>
> > > > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/drm_crtc.c | 10 +++++++---
> > > > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/drm_crtc.c
> > > > > b/drivers/gpu/drm/drm_crtc.c
> > > > > index 70f9c68..3a32606 100644
> > > > > --- a/drivers/gpu/drm/drm_crtc.c
> > > > > +++ b/drivers/gpu/drm/drm_crtc.c
> > > > > @@ -5610,8 +5610,8 @@ void drm_fb_get_bpp_depth(uint32_t
> > > > > format,
> > > > > unsigned int *depth,
> > > > >  		*bpp = 32;
> > > > >  		break;
> > > > >  	default:
> > > > > -		DRM_DEBUG_KMS("unsupported pixel format %s\n",
> > > > > -			      drm_get_format_name(format));
> > > > > +		WARN(1, "unsupported pixel format %s\n",
> > > > > +		     drm_get_format_name(format));
> > > > 
> > > > NAK. This will happen every time drm_helper_mode_fill_fb_struct()
> > > > is called with a non-RGB format.
> > > 
> > > Yep, missed that. So how about handling here those formats
> > > explicitly,
> > > and emitting a warning only for truly unsupported formats?
> > 
> > More work to keep this list updated, and it wouldn't prevent any
> > div-by-zero with those formats. So I don't really see a point in
> > that.
> 
> It would avoid the incorrect 'unsupported pixel format' message for
> those.

If that's the entire concern, delete it. New drivers shouldn't use these
functions any more anyway.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch