[RFC PATCH v3 0/3] Support for Solid Fill Planes

[Jessica Zhang]

On 1/5/2023 3:33 AM, Daniel Vetter wrote:
> On Wed, Jan 04, 2023 at 03:40:33PM -0800, Jessica Zhang wrote:
>> Introduce and add support for a solid_fill property. When the solid_fill
>> property is set, and the framebuffer is set to NULL, memory fetch will be
>> disabled.
>>
>> In addition, loosen the NULL FB checks within the atomic commit callstack
>> to allow a NULL FB when the solid_fill property is set and add FB checks
>> in methods where the FB was previously assumed to be non-NULL.
>>
>> Finally, have the DPU driver use drm_plane_state.solid_fill and instead of
>> dpu_plane_state.color_fill, and add extra checks in the DPU atomic commit
>> callstack to account for a NULL FB in cases where solid_fill is set.
>>
>> Some drivers support hardware that have optimizations for solid fill
>> planes. This series aims to expose these capabilities to userspace as
>> some compositors have a solid fill flag (ex. SOLID_COLOR in the Android
>> hardware composer HAL) that can be set by apps like the Android Gears
>> app.
>>
>> Userspace can set the solid_fill property to a blob containing the
>> appropriate version number and solid fill color (in RGB323232 format) and
>> setting the framebuffer to NULL.
>>
>> Note: Currently, there's only one version of the solid_fill blob property.
>> However if other drivers want to support a similar feature, but require
>> more than just the solid fill color, they can extend this feature by
>> creating additional versions of the drm_solid_fill struct.
>>
>> Changes in V2:
>> - Dropped SOLID_FILL_FORMAT property (Simon)
>> - Switched to implementing solid_fill property as a blob (Simon, Dmitry)
>> - Changed to checks for if solid_fill_blob is set (Dmitry)
>> - Abstracted (plane_state && !solid_fill_blob) checks to helper method
>>    (Dmitry)
>> - Removed DPU_PLANE_COLOR_FILL_FLAG
>> - Fixed whitespace and indentation issues (Dmitry)
> 
> Now that this is a blob, I do wonder again whether it's not cleaner to set
> the blob as the FB pointer. Or create some kind other kind of special data
> source objects (because solid fill is by far not the only such thing).
> 
> We'd still end up in special cases like when userspace that doesn't
> understand solid fill tries to read out such a framebuffer, but these
> cases already exist anyway for lack of priviledges.
> 
> So I still think that feels like the more consistent way to integrate this
> feature. Which doesn't mean it has to happen like that, but the
> patches/cover letter should at least explain why we don't do it like this.

Hi Daniel,

IIRC we were facing some issues with this check [1] when trying to set 
FB to a PROP_BLOB instead. Which is why we went with making it a 
separate property instead. Will mention this in the cover letter.

[1] 
https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/drm_property.c#L71

Thanks,

Jessica Zhang

> -Daniel
> 
>>
>> Changes in V3:
>> - Fixed some logic errors in atomic checks (Dmitry)
>> - Introduced drm_plane_has_visible_data() and drm_atomic_check_fb() helper
>>    methods (Dmitry)
>>
>> Jessica Zhang (3):
>>    drm: Introduce solid fill property for drm plane
>>    drm: Adjust atomic checks for solid fill color
>>    drm/msm/dpu: Use color_fill property for DPU planes
>>
>>   drivers/gpu/drm/drm_atomic.c              | 136 +++++++++++++---------
>>   drivers/gpu/drm/drm_atomic_helper.c       |  34 +++---
>>   drivers/gpu/drm/drm_atomic_state_helper.c |   9 ++
>>   drivers/gpu/drm/drm_atomic_uapi.c         |  59 ++++++++++
>>   drivers/gpu/drm/drm_blend.c               |  17 +++
>>   drivers/gpu/drm/drm_plane.c               |   8 +-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c  |   9 +-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c |  65 +++++++----
>>   include/drm/drm_atomic_helper.h           |   5 +-
>>   include/drm/drm_blend.h                   |   1 +
>>   include/drm/drm_plane.h                   |  62 ++++++++++
>>   11 files changed, 302 insertions(+), 103 deletions(-)
>>
>> -- 
>> 2.38.1
>>
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch