Re: [PATCH v3] drm: Guard DRM_CLIENT_CAP_PLANE_COLOR_PIPELINE

[Robert Mader <robert.mader@collabora.com>]

Hi,

On 07.07.26 15:01, Maarten Lankhorst wrote:
> Hey,
>
> On 7/7/26 10:03, Borah, Chaitanya Kumar wrote:
>>
>> On 7/3/2026 1:02 PM, Robert Mader wrote:
>>> The client cap is currently advertised unconditionally, even for drivers
>>> that do not support plane color pipelines. If clients supporting the later,
>> s/later/latter
>>
>>> like Wayland compositors or tools like drm_info, enable the client cap on
>>> such drivers they will be left without both color pipeline and the legacy
>>> properties COLOR_ENCODING and COLOR_RANGE, effectively breaking YUV->RGB
>>> conversion support.
>>>
>>> Prevent that by only marking the cap supported if there are actually planes
>>> with color pipelines.
>>>
>>> Note: while the color pipeline replacement for the legacy properties is
>>> still under review (1), we can assume that it will work as a drop-in
>>> replacement.
>> This change will but a driver can also choose to export colorops like programmable CTM_3x4 to achieve the same.
>>
>> We should also perhaps document this somewhere that if a driver supports LEGACY properties, it is imperative to implement some version of it with the color pipeline line property.
> Would this be doable inside drm core? Implement the color pipeline properties, get the fixed pipeline for free?
>
> But thanks for all feedback, as I was about to push this patch, I noticed it still uses -EOPNOTSUPP, can it be changed to -EINVAL?

For existing users it shouldn't make a difference. drm_info and Weston 
just check for "drmSetClientCap() == 0" - and old kernels without the 
cap will also return -EINVAL AFAICS.

I personally find -EOPNOTSUPP more appropriate and more in line with 
other return values in that function - but no strong opinion, thus feel 
free to change while applying (or I can resend the patch accordingly if 
you prefer).

Robert

>
> ~Maarten

-- 
Robert Mader
Consultant Software Developer

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