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| author | Dave Airlie <airlied@redhat.com> | 2016-03-23 23:41:59 +0100 |
|---|---|---|
| committer | Dave Airlie <airlied@redhat.com> | 2016-03-23 23:41:59 +0100 |
| commit | 17efca93c8728445522dedafc033b3384a26a39d (patch) | |
| tree | 44c3b4a4e24a202077f4746fb240c850d86f8853 /Documentation | |
| parent | drm/amdgpu: release_pages requires linux/pagemap.h (diff) | |
| parent | dma-buf/fence: fix fence_is_later v2 (diff) | |
| download | linux-17efca93c8728445522dedafc033b3384a26a39d.tar.xz linux-17efca93c8728445522dedafc033b3384a26a39d.zip | |
Merge tag 'topic/drm-misc-2016-03-22' of git://anongit.freedesktop.org/drm-intel into drm-next
Bunch of small fixupes all over. Plus a dma-buf patch that Sumit asked me
to cherry-pick since that's the only one he had in his tree.
There's a sparse issue outstanding in the color mgr stuff, but Lionel is
still working on something that actually appeases sparse.
* tag 'topic/drm-misc-2016-03-22' of git://anongit.freedesktop.org/drm-intel:
dma-buf/fence: fix fence_is_later v2
dma-buf: Update docs for SYNC ioctl
drm: remove excess description
dma-buf, drm, ion: Propagate error code from dma_buf_start_cpu_access()
drm/atmel-hlcdc: use helper to get crtc state
drm/atomic: use helper to get crtc state
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/dma-buf-sharing.txt | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 32ac32e773e1..ca44c5820585 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -352,7 +352,8 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: No special interfaces, userspace simply calls mmap on the dma-buf fd, making sure that the cache synchronization ioctl (DMA_BUF_IOCTL_SYNC) is *always* - used when the access happens. This is discussed next paragraphs. + used when the access happens. Note that DMA_BUF_IOCTL_SYNC can fail with + -EAGAIN or -EINTR, in which case it must be restarted. Some systems might need some sort of cache coherency management e.g. when CPU and GPU domains are being accessed through dma-buf at the same time. To @@ -366,10 +367,10 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: want (with the new data being consumed by the GPU or say scanout device) - munmap once you don't need the buffer any more - Therefore, for correctness and optimal performance, systems with the memory - cache shared by the GPU and CPU i.e. the "coherent" and also the - "incoherent" are always required to use SYNC_START and SYNC_END before and - after, respectively, when accessing the mapped address. + For correctness and optimal performance, it is always required to use + SYNC_START and SYNC_END before and after, respectively, when accessing the + mapped address. Userspace cannot rely on coherent access, even when there + are systems where it just works without calling these ioctls. 2. Supporting existing mmap interfaces in importers |