[PATCH v6 6/6] drm/doc: Define KMS atomic state set

[Michel Dänzer]

On 8/21/23 22:02, André Almeida wrote:
> Em 17/08/2023 07:37, Michel Dänzer escreveu:
>> On 8/15/23 20:57, André Almeida wrote:
>>> From: Pekka Paalanen <pekka.paalanen at collabora.com>
>>>
>>> Specify how the atomic state is maintained between userspace and
>>> kernel, plus the special case for async flips.
>>>
>>> Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.com>
>>> Signed-off-by: André Almeida <andrealmeid at igalia.com>
>>
>> [...]
>>
>>> +An atomic commit with the flag DRM_MODE_PAGE_FLIP_ASYNC is allowed to
>>> +effectively change only the FB_ID property on any planes. No-operation changes
>>> +are ignored as always. [...]
>>
>> During the hackfest in Brno, it was mentioned that a commit which re-sets the same FB_ID could actually have an effect with VRR: It could trigger scanout of the next frame before vertical blank has reached its maximum duration. Some kind of mechanism is required for this in order to allow user space to perform low frame rate compensation.
>>
> 
> I believe the documentation already addresses that sending redundant information may not lead to the desired behavior during an async flip. Do you think adding a note about using the same FB_ID would be helpful?

Maybe not.


-- 
Earthling Michel Dänzer            |                  https://redhat.com
Libre software enthusiast          |         Mesa and Xwayland developer