[RFC PATCH 1/3] drm: Introduce color fill properties for drm plane

[Daniel Vetter]

On Tue, Nov 08, 2022 at 06:25:29PM +0000, Simon Ser wrote:
> On Saturday, October 29th, 2022 at 13:23, Dmitry Baryshkov <dmitry.baryshkov at linaro.org> wrote:
> 
> > On 29/10/2022 01:59, Jessica Zhang wrote:
> > 
> > > Add support for COLOR_FILL and COLOR_FILL_FORMAT properties for
> > > drm_plane. In addition, add support for setting and getting the values
> > > of these properties.
> > > 
> > > COLOR_FILL represents the color fill of a plane while COLOR_FILL_FORMAT
> > > represents the format of the color fill. Userspace can set enable solid
> > > fill on a plane by assigning COLOR_FILL to a uint64_t value, assigning
> > > the COLOR_FILL_FORMAT property to a uint32_t value, and setting the
> > > framebuffer to NULL.
> > 
> > I suppose that COLOR_FILL should override framebuffer rather than
> > requiring that FB is set to NULL. In other words, if color_filL_format
> > is non-zero, it would make sense to ignore the FB. Then one can use the
> > color_fill_format property to quickly switch between filled plane and
> > FB-backed one.
> 
> That would be inconsistent with the rest of the KMS uAPI. For instance,
> the kernel will error out if CRTC has active=0 but a connector is still
> linked to the CRTC. IOW, the current uAPI errors out if the KMS state
> is inconsistent.

So if the use-case here really is to solid-fill a plane (and not just
provide a background color for the crtc overall), then I guess we could
also extend addfb to make that happen. We've talked in the past about
propertery-fying framebuffer objects, and that would sort out this uapi
wart. And I agree the color fill vs PLANE_ID issue is a bit ugly at least.

But if the use-cases are all background color then just doing the crtc
background color would be tons simpler (and likely also easier to support
for more hardware).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch