Re: [PATCH 0/4] Adding support for plane alpha/color blending through drm property

[Sagar Arun Kamble <sagar.a.kamble@intel.com>]

Hi Damien,

Could you please clarify following queries.

Thanks,
Sagar
On Fri, 2014-03-21 at 19:06 +0530, Sagar Arun Kamble wrote:
> 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
> 
>