On Fri, Nov 1, 2013 at 12:00 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Thu, Oct 31, 2013 at 10:07:25PM +0100, Thomas Hellstrom wrote: >> On 10/31/2013 09:48 PM, Dave Airlie wrote: >> >On Fri, Nov 1, 2013 at 6:40 AM, Thomas Hellstrom <thellstrom@xxxxxxxxxx> wrote: >> >>Well, I'd be happy to avoid mmap, but then what does optional mean in this >> >>context? >> >>That all generic user-space apps *must* implement a workaround if mmap isn't >> >>implemented? >> >> >> >>It's unfortunate a bit like implicit synchronization mentioned in section 3) >> >>in Direct Userspace Access/mmap Support >> >>in the kernel dma-buf doc: It should be avoided, otherwise it might be >> >>relied upon by userspace and exporters >> >>not implementing it will suffer. >> >> >> >>In reality, people will start using mmap() and won't care to implement >> >>workarounds if it's not supported, and drivers like >> >>vmwgfx and non-coherent architectures will suffer. >> >> >> >>I haven't looked closely at how DRI3 or Wayland/weston use or will use >> >>dma-buf, but if they rely on mmap, we're sort >> >>of lost. MIR uses the following scheme: >> >DRI3 and wayland won't use dma-buf mmap directly, >> > >> >using dma-buf mmap directly is wrong for anything that shares objects >> >with itself. >> >> That sounds good to hear. Perhaps we should add that to the dma-buf docs. > > Userspace mmap was essentially added as a concession to the android ion > guys since they really, really wanted it. We've tried to tell them that > it's a horrible idea (see all the fun with coherency and syncing), but > they said that they have userspace for it already and so we let it be. > > Imo if you're not running Android userspace there's no need for this at > all. But now it turns out that gstreamer is using it and our life is hell. We should have made it not work for _any_ driver if CONFIG_ANDRIOD wasn't set. Cheers, Jakob. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
