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

[Dmitry Baryshkov]

On 09/11/2022 16:52, Daniel Vetter wrote:
> 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).

No. The hardware supports multiple color-filled planes, which do not 
have to cover the whole CRTC.

-- 
With best wishes
Dmitry