wayland/dmabuf: Stop resending feedback if the client already uses an optimal format/modifier combination
Edit: See https://gitlab.freedesktop.org/wayland/wayland-protocols/-/issues/90 for upstream discussion
From the spec:
Compositors should not re-send the parameters if re-allocating the buffers would not result in a more optimal configuration.
This is slightly in conflict with
The parameters are sent once when this object is created and whenever they change.
Mesa and Weston both interpret it the way that resending a feedback with a scanout tranche is a signal to the client to reallocate its buffers - and that this should not be done if scanout is already successful with the previously used configuration. I'm not sure if this is ever a real problem but in theory it could lead to excessive reallocation on the GPU.
An unfortunate side-effect of this would be that weston-simple-dmabuf-feedback
wouldn't print the scanout tranche info any more.