[Intel-gfx] [PATCH 0/4] Adding support for plane alpha/color blending through drm property

[Sagar Arun Kamble]

Hi Damien,

On Thu, 2014-03-20 at 14:45 +0000, Damien Lespiau wrote:
> On Thu, Mar 20, 2014 at 02:11:40PM +0000, Damien Lespiau wrote:
> > (source is premultiplied)
> > 
> > RGBA = ADD(SRC_COLOR*SRC_ALPHA, DST_COLOR*ONE_MINUS_SRC_ALPHA)
> 
> Grr, copy/paste error. If the source is already premultiplied:
> 
> RGBA = ADD(SRC_COLOR, DST_COLOR*ONE_MINUS_SRC_ALPHA)
> 

1. Currently there is no interface to advertise the DRM_FORMATS plane
supportes to user mode? Should we add new IOCTL for that and include
pre-multiplied alpha formats while advertising? Or am I missing any such
API already available?

2. About constant alpha property - when we program constant alpha
register will hardware be able to take care of the blending as per
equations you have specified for non-premultiplied-alpha and
premultiplied-alpha cases or we have to do any additional setting?
Confusion is because of two combinations:
a. pre-multiplied alpha+constant alpha
b. non-pre-multiplied alpha+constant alpha

Kindly clarify.

thanks,
Sagar