[PATCH v3 09/15] drm: tilcdc: Replace drm_fb_get_bpp_depth() with drm_format_plane_cpp()

[Tomi Valkeinen]

On 10/06/16 15:05, Ville Syrjälä wrote:

>> I'm not sure what's the common way, but tilcdc doesn't support alpha.
>> ARGB works, of course, by ignoring A, but... If an userspace app creates
>> ARGB buffer, does the app expect alpha to work?
> 
> I think what we decided a while ago (at least for i915, but would be good
> to use the same convention everywhere) was that ARGB will be assumed to be
> pre-multiplied and will enable blending using 1.0*sc+(1.0-sa)*dc as the
> function. There have been some efforts at defining some new properties to
> control the blend equation, but I guess those got bogged down again.

Ok, but that's a bit different topic. The question here is, if the HW
doesn't support alpha (no planes, so nothing to blend), should it accept
ARGB or not.

 Tomi

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