On Sat, Jan 2, 2021 at 7:51 PM Ilia Mirkin <imirkin@xxxxxxxxxxxx> wrote:
On Sat, Jan 2, 2021 at 1:35 PM Mario Kleiner <mario.kleiner.de@xxxxxxxxx> wrote:
> I'm less sure about nouveau. It uses modifiers, but has atomic support
> only on nv50+ and that atomic support is off by default -- needs a
> nouveau.nouveau_atomic=1 boot parameter to switch it on. It seems to
> enable modifier support unconditionally regardless if atomic or not,
> see:
> https://elixir.bootlin.com/linux/v5.11-rc1/source/drivers/gpu/drm/nouveau/nouveau_display.c#L703
>
> Atm. nouveau doesn't assign a new format_info though, so wouldn't
> trigger this issue atm.
Note that pre-nv50, no modifiers exist. Also,
drm_drv_uses_atomic_modeset() doesn't care whether the client is an
atomic client or not. It will return true for nv50+ no matter what.
nouveau_atomic=1 affects whether atomic UAPI is exposed. Not sure if
this impacts your discussion.
Thanks Ilia. So nouveau is fine in any case, as nv50 => modifiers and atomic commit even if atomic UAPI is off. Also drm_drv_uses_atomic_modeset() is the right choice, as my patch should check if the atomic driver uses atomic commit, it doesn't care about atomic UAPI or the client being atomic.
-mario
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