On Mon, 16 Oct 2023 12:52:32 +0200 André Almeida <andrealm...@igalia.com> wrote:
> Hi Michel, > > On 8/17/23 12:37, Michel Dänzer wrote: > > On 8/15/23 20:57, André Almeida wrote: > >> From: Pekka Paalanen <pekka.paala...@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.paala...@collabora.com> > >> Signed-off-by: André Almeida <andrealm...@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. > > > Xaver tested this hypothesis in a flipping the same fb in a VRR monitor > and it worked as expected, so this shouldn't be a concern. Right, so it must have some effect. It cannot be simply ignored like in the proposed doc wording. Do we special-case re-setting the same FB_ID as "not a no-op" or "not ignored" or some other way? Thanks, pq
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