Am Dienstag, den 04.04.2017, 20:27 +1000 schrieb Christopher James Halse Rogers: > On 4 April 2017 6:31:12 pm AEST, Daniel Vetter <daniel@xxxxxxxx> wrote: > >On Tue, Apr 04, 2017 at 06:13:20PM +1000, raof@xxxxxxxxxx wrote: > >> From: Christopher James Halse Rogers <raof@xxxxxxxxxx> > >> > >> Until recently, on (at least) nouveau, radeon, and amdgpu attempting > >to scanout of an > >> imported dma-buf would silently result in the dma-buf sharing being > >broken. > >> > >> While the hardware is capable of scanning out of imported dma-bufs > >(at least in some circumstances), > >> these drivers do not currently implement it, so attempts to scan out > >of such buffers will never succeed. > >> > >> Add a userspace-visible drm capability and associated driver_feature > >so that userspace can discover > >> when scanning out of an imported dma-buf can work. > >> > >> Signed-off-by: Christopher James Halse Rogers > ><christopher.halse.rogers@xxxxxxxxxxxxx> > > > >This seems like an awful specific special case. Why can't you do the > >entire dance upfront, i.e. import buffer, addfb2? None of that has any > >visible effect, and it will also allow you to check runtime constraints > >which can't be covered with this here. > >-Daniel > > No, because addfb2 doesn't (or, rather, didn't) actually check any > runtime constraints. > > The problem only appeared when the buffer is actually *used* in a > modeset - otherwise I could do a (reasonably) cheap > import/addfb/render on exporter/read out on importer dance to detect > it. > > To be clear - this is trying to solve the problem “how can I tell if > it's safe to addfb/pageflip rather than do a GL copy to a GPU-local > buffer and flip from that?”. > > If I could guarantee that I'd only ever run on 4.13-or-later kernels > (I think that's when the previous patches will land?), then this would > indeed be mostly unnecessary. It would save me a bunch of addfb calls > that would predictably fail, but they're cheap. I don't think we ever had caps for "things are working now, as they are supposed to". i915 wasn't properly synchronizing on foreign fences for a long time, yet we didn't gain a cap for "cross device sync works now". If your distro use-case relies on those things working it's probably best to just backport the relevant fixes. Regards, Lucas _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
