Ville Syrjälä ville.syrjala@linux.intel.com writes:
On Fri, Mar 02, 2018 at 04:06:58PM +0100, Stefan Schake wrote:
Hey Ville,
On Fri, Mar 2, 2018 at 3:43 PM, Ville Syrjälä ville.syrjala@linux.intel.com wrote:
On Fri, Mar 02, 2018 at 04:39:22PM +0200, Ville Syrjälä wrote:
If you want the plane to always be opaque you shouldn't expose any formats with alpha.
Also what happens if one disables the primary plane? Or does the driver not allow that?
Or just makes the plane not cover the entire screen?
We've exposed alpha formats in the past so disabling that now would break userspace, certainly Android that chooses alpha-everything.
So it refuses to even run on hardware that can't do per-pixel alpha on the primary plane?
The VC4 HVS has no fixed planes so I'll acknowledge that the concept of a primary plane is somewhat dubious and userspace could disable it or make it not cover the entire screen, making this ineffective.
But then ultimately there doesn't seem to be a standard for what the display is supposed to be if you have transparent pixels with no plane to blend to below.
The standard is black. IMO it's a driver bug if it fails to do that.
If the plane is premultiplied (isn't that what DRM planes are supposed to be? I can't find any docs), then blending against black is the same as not doing any blending at all.