Re: [QUESTION] drmModeAtomicCommit returns -EINVAL on return

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4. Do I need to wait for vblank for modesetting? I know it will be an

error if I tried to do drmModePageFlip before the last one is handled but what about drmModeSetCrtc? Do I need to wait for a vblank for the last pageflip?

Right now, if you don't wait for any pending page flip to complete before drmModeSetCrtc, the two may race, and the CRTC may end up scanning out from the FB set by the page flip.

Maybe this race should be prevented in the kernel though.

Maybe this could happen on non-atomic drivers, but on atomic drivers there's no race, the setcrtc will wait for the previous pageflip to complete first. Ofc if you call both from 2 threads at the same time then either could win, but if you do one after the other there's no ordering issues with atomic drivers. -Daniel