> > The part where we get this independent of attached hardware is quite > > important for us though, since we can't just ignore explicit sync once > > the device we previously imported the syncobj into is disconnected. > > Can you elaborate more on this?
In Wayland, the client is allowed to attach dmabuf and syncobj independently, they don't have to be from the same device (and the compositor wouldn't be able to verify the opposite anyways). The compositor will usually import both into the same drm device, but especially with compositors that render on multiple devices, that's not necessarily the case either. If for example we had a system with one internal GPU and one external GPU, the client renders on the internal GPU and the compositor uses the external one. Now when the user yanks the USB C cable, afaiu - the buffers from the client stay valid - the syncobj stays valid on the client side - the syncobj becomes invalid on the compositor side "invalid" there means either - the acquire point of the client is marked as signaled, before rendering on the client side is completed - the acquire point of the client is never signaled. Since the compositor waits for the acquire point, the Wayland surface is stuck forever Afaik the latter is currently the case. The former wouldn't be much better though, not when it's preventable. This is admittedly an edge case, but GPU hotunplug is something we try to support as well as possible in Plasma, and all the edge cases cause a lot of problems in combination and are a lot of headaches to handle (or really work around) in the compositor. Another edge case is when the client asks the compositor to import the syncobj, which can fail when a hotunplug is in process, and ends up disconnecting the client for no fault of either client or compositor. > >>> 3. It removes the need to translate between syncobjs fds and handles. > >> > >> That's a pretty big no-go as well. The differentiation between FDs and > >> handles is completely intentional. > > Could you expand on why it's needed? For compositors, the handle is > > just an intermediary thing when translating between file descriptors. > > Well what we could do is to add an IOCTL to directly attach an syncobj file > descriptor to an eventfd. That would be nice. - Xaver
