On Tue, Jun 14, 2016 at 07:53:41AM +0200, Daniel Vetter wrote: > On Tue, Jun 14, 2016 at 11:09:10AM +0900, Michel Dänzer wrote: > > E.g.: In cases where page flipping cannot be used, Xorg / the DDX driver > > waits for the target vertical blank period before emitting the drawing > > commands for a buffer swap operation. If the vblank notification only > > arrives when the vertical blank period is already over, this is very > > likely to result in tearing. > > > > Some X compositors and AFAIK even applications such as media players can > > use DRM_IOCTL_WAIT_VBLANK similarly. Obviously it's not intended to be > > used directly like that, but nonetheless it is. > > Is there really anything using it like that outside of -ati? I didn't know > that we pass vblank waits to X clients. No, because EGL doesn't offer an equivalent to OML_sync_control applications like kodi have implemented their own vblank scheduling via DRM_IOCTL_WAIT_VBLANK directly. > Either way annoying, since it > means you need to keep things working like this for amd drivers forever. > Afaik others don't use it like that, at least not on intel. Weston has > some hacks to use vblank waits for plane flips, but that's all disabled > code because it just doesn't work - you need full atomic. Inside Xorg/Present, as Michel said, the vblank notification is used to drive onscreen copies *within* the vblank period (i.e. to try and avoid visible tearing). -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
