On Fri, Apr 29, 2016 at 3:48 AM, Daniel Stone <daniel@xxxxxxxxxxxxx> wrote: > Hi, > > On 28 April 2016 at 23:28, Rob Clark <robdclark@xxxxxxxxx> wrote: >> On Wed, Apr 27, 2016 at 2:39 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: >>> On Tue, Apr 26, 2016 at 01:48:02PM -0700, Greg Hackmann wrote: >>>> A (per-CRTC?) array of fences would be more flexible. And even in the cases >>>> where you could make a 1-to-1 mapping between planes and fences, it's not >>>> that much more work for userspace to assemble those fences into an array >>>> anyway. >>> >>> I'm ok with an array too if that's what you folks prefer (it's meant to be >>> used by you after all). I just don't want just 1 fence for the entire op, >>> forcing userspace to first merge them all together. That seems silly. >> >> I was kinda more a fan of array too, if for no other reason that to be >> consistent w/ how out-fences work. (And using property just for >> in-fence seemed slightly weird/abusive to me) > > I don't think it's really useful to look for much consistency between > the two, beyond the name. I'm more concerned with consistency between > in-fences and the implicit fences on buffers/FBs, and between > out-fences and the page_flip_events. > >>> One side-effect of that is that we'd also have to rework all the internal >>> bits and move fences around in atomic. Which means change a pile of >>> drivers. Not sure that's worth it, but I'd be ok either way really. >> >> hmm, well we could keep the array per-plane (and if one layer is using >> multiple planes, just list the same fd multiple times).. then it >> mostly comes down to changes in the ioctl fxn itself. > > ... and new API in libdrm, which is going to be a serious #ifdef and > distribution pain. The core property API has been available since > 2.4.62 last June, but for this we'd have to write the code, wait for > the kernel code, wait for HWC, get everything together, and then merge > and release. That gives minimum one year of libdrm releases which have > had atomic but not in-fence API support, if we're adding a new array. > And I just don't really see what it buys us, apart from the need for > the core atomic_get_property helper to statically return -1 when > requesting FENCE_FD. don't we have the same issue for out-fences anyway? ofc, I suspect we could handle making fences look like properties in userspace in libdrm (at least if there was a sane way that libdrm could track and eventually close() old out-fence fd's). I'm not entirely sure this matters, I mean how do we make implicit vs explicit fencing transparent to the compositor and the proto between compositor<->app? Admittedly I haven't given *too* much thought yet about the implications to libdrm and it's users, but it seems like we need to make a v2 API rev anyway for out-fences, and the compositor is going to need different codepaths for explicit vs implicit (if it supports both). So I don't think in-fences as something other than property really costs us anything additional? (Unless there is some sane reason to have an intermediate state w/ in-fences but pageflip events instead of out-fences? But that seems odd..) BR, -R > Cheers, > Daniel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
