On Fri, Nov 1, 2013 at 1:25 AM, Rob Clark <robdclark@xxxxxxxxx> wrote: > On Thu, Oct 31, 2013 at 8:17 PM, Jakob Bornecrantz <wallbraker@xxxxxxxxx> wrote: >> 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. > > well, at the moment mmap is only implemented by a few of the arm > drivers, from the looks of it. So I guess in the near term it is > mostly going to be of interest to the SoC crowd. Ah okay, I thought this was desktop gstreamer. > Not sure about the long term, perhaps we should see about > turning gallium pipe_transfer/map stuff into a kernel interface > (ioctl's directly on the dmabuf fd, perhaps?) Or they could just create a OpenGL context, I know it sounds heavy weight. But somebody will eventually want to synchronize this with a different client API in a non-blocking way. And OpenGL or some other Khronos API already have that integration, no real need to reinvent the wheel. Then again I think both GBM and DRI have hooks for mapping and unmapping buffers, so those might suffice. Cheers, Jakob. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
