Re: [PATCH RFC v5 02/10] drm: Introduce solid fill DRM plane property

[Dmitry Baryshkov]

On Tue, 29 Aug 2023 at 02:45, Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
>
>
>
> On 8/8/2023 3:57 PM, Jessica Zhang wrote:
> >
> >
> > On 8/7/2023 6:07 PM, Dmitry Baryshkov wrote:
> >>
> >>
> >> On 8 August 2023 00:41:07 GMT+03:00, Jessica Zhang
> >> <quic_jesszhan@xxxxxxxxxxx> wrote:
> >>>
> >>>
> >>> On 8/4/2023 6:27 AM, Dmitry Baryshkov wrote:
> >>>> On Fri, 28 Jul 2023 at 20:03, Jessica Zhang
> >>>> <quic_jesszhan@xxxxxxxxxxx> wrote:
> >>>>>
> >>>>> Document and add support for solid_fill property to drm_plane. In
> >>>>> addition, add support for setting and getting the values for
> >>>>> solid_fill.
> >>>>>
> >>>>> To enable solid fill planes, userspace must assign a property blob to
> >>>>> the "solid_fill" plane property containing the following information:
> >>>>>
> >>>>> struct drm_mode_solid_fill {
> >>>>>           u32 version;
> >>>>>           u32 r, g, b;
> >>>>> };
> >>>>>
> >>>>> Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> >>>>> ---
> >>>>>    drivers/gpu/drm/drm_atomic_state_helper.c |  9 +++++
> >>>>>    drivers/gpu/drm/drm_atomic_uapi.c         | 55
> >>>>> +++++++++++++++++++++++++++++++
> >>>>>    drivers/gpu/drm/drm_blend.c               | 30 +++++++++++++++++
> >>>>>    include/drm/drm_blend.h                   |  1 +
> >>>>>    include/drm/drm_plane.h                   | 35 ++++++++++++++++++++
> >>>>>    include/uapi/drm/drm_mode.h               | 24 ++++++++++++++
> >>>>>    6 files changed, 154 insertions(+)
> >>>>>
> >>>>
> >>>> [skipped most of the patch]
> >>>>
> >>>>> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> >>>>> index 43691058d28f..53c8efa5ad7f 100644
> >>>>> --- a/include/uapi/drm/drm_mode.h
> >>>>> +++ b/include/uapi/drm/drm_mode.h
> >>>>> @@ -259,6 +259,30 @@ struct drm_mode_modeinfo {
> >>>>>           char name[DRM_DISPLAY_MODE_LEN];
> >>>>>    };
> >>>>>
> >>>>> +/**
> >>>>> + * struct drm_mode_solid_fill - User info for solid fill planes
> >>>>> + *
> >>>>> + * This is the userspace API solid fill information structure.
> >>>>> + *
> >>>>> + * Userspace can enable solid fill planes by assigning the plane
> >>>>> "solid_fill"
> >>>>> + * property to a blob containing a single drm_mode_solid_fill
> >>>>> struct populated with an RGB323232
> >>>>> + * color and setting the pixel source to "SOLID_FILL".
> >>>>> + *
> >>>>> + * For information on the plane property, see
> >>>>> drm_plane_create_solid_fill_property()
> >>>>> + *
> >>>>> + * @version: Version of the blob. Currently, there is only support
> >>>>> for version == 1
> >>>>> + * @r: Red color value of single pixel
> >>>>> + * @g: Green color value of single pixel
> >>>>> + * @b: Blue color value of single pixel
> >>>>> + */
> >>>>> +struct drm_mode_solid_fill {
> >>>>> +       __u32 version;
> >>>>> +       __u32 r;
> >>>>> +       __u32 g;
> >>>>> +       __u32 b;
> >>>>
> >>>> Another thought about the drm_mode_solid_fill uABI. I still think we
> >>>> should add alpha here. The reason is the following:
> >>>>
> >>>> It is true that we have  drm_plane_state::alpha and the plane's
> >>>> "alpha" property. However it is documented as "the plane-wide opacity
> >>>> [...] It can be combined with pixel alpha. The pixel values in the
> >>>> framebuffers are expected to not be pre-multiplied by the global alpha
> >>>> associated to the plane.".
> >>>>
> >>>> I can imagine a use case, when a user might want to enable plane-wide
> >>>> opacity, set "pixel blend mode" to "Coverage" and then switch between
> >>>> partially opaque framebuffer and partially opaque solid-fill without
> >>>> touching the plane's alpha value.
> >>>
> >>> Hi Dmitry,
> >>>
> >>> I don't really agree that adding a solid fill alpha would be a good
> >>> idea. Since the intent behind solid fill is to have a single color
> >>> for the entire plane, I think it makes more sense to have solid fill
> >>> rely on the global plane alpha.
> >>>
> >>> As stated in earlier discussions, I think having both a
> >>> solid_fill.alpha and a plane_state.alpha would be redundant and serve
> >>> to confuse the user as to which one to set.
> >>
> >> That depends on the blending mode: in Coverage mode one has
> >> independent plane and contents alpha values. And I consider alpha
> >> value to be a part of the colour in the rgba/bgra modes.
> >
> > Acked -- taking Sebastian's concern into consideration, I think I'll
> > have "PIXEL_SOURCE_SOLID_FILL_RGB" and add a separate
> > "PIXEL_SOURCE_SOLID_FILL_RGBA".
>
> Hi Dmitry,
>
> Since it looks like there's still some ongoing discussion with Pekka
> about whether to support an RGBA solid fill source, I'll just leave a
> note to add an RGBA source in the future.

Sure! Let's get the basic framework landed. After that we can extend
it with RGBA, if that seems sensible.

>
> Thanks,
>
> Jessica Zhang
>
> >
> > Thanks,
> >
> > Jessica Zhang
> >
> >>
> >>
> >>>
> >>> Thanks,
> >>>
> >>> Jessica Zhang
> >>>
> >>>>
> >>>> --
> >>>> With best wishes
> >>>> Dmitry
> >>
> >> --
> >> With best wishes
> >> Dmitry



-- 
With best wishes
Dmitry