Hi Daniel
Thanks for looking into this series.
On 1/6/2023 1:49 PM, Dmitry Baryshkov wrote:
On Fri, 6 Jan 2023 at 20:41, Daniel Vetter <daniel@xxxxxxxx> wrote:
On Fri, Jan 06, 2023 at 05:43:23AM +0200, Dmitry Baryshkov wrote:
On Fri, 6 Jan 2023 at 02:38, Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:
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.
What kind of issues? Could you please describe them?
We switched from bitmask to enum style for prop types, which means it's
not possible to express with the current uapi a property which accepts
both an object or a blob.
Which yeah sucks a bit ...
But!
blob properties are kms objects (like framebuffers), so it should be
possible to stuff a blob into an object property as-is. Of course you need
to update the validation code to make sure we accept either an fb or a
blob for the internal representation. But that kind of split internally is
required no matter what I think.
I checked your idea and notes from Jessica. So while we can pass blobs
to property objects, the prop_fb_id is created as an object property
with the type DRM_MODE_OBJECT_FB. Passing DRM_MODE_OBJECT_BLOB would
fail a check in drm_property_change_valid_get() ->
__drm_mode_object_find(). And I don't think that we should break the
existing validation code for this special case.
Like Jessica wrote, re-using the FB_ID property to pass solid fill
information will need modification of existing checks shown in [1] OR
the property creation itself would fail.
We just went with this approach, as it was less intrusive and would not
affect the existing FB_ID path.
Since both approaches need modifications of validation checks, adding a
new property is less intrusive and safer than the already convoluted
checks in drm_property_flags_valid().
Let us know if its a strong preference on your side to re-use FB_ID and
if so why.
Thanks
Abhinav
If you insist on using FB_ID for passing solid_fill information, I'd
ask you to reconsider using a 1x1 framebuffer. It would be fully
compatible with the existing userspace, which can then treat it
seamlessly.
-Daniel
[1]
https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/drm_property.c#L71
