|author||Dave Airlie <email@example.com>||2016-03-24 08:41:59 +1000|
|committer||Dave Airlie <firstname.lastname@example.org>||2016-03-24 08:41:59 +1000|
|parent||drm/amdgpu: release_pages requires linux/pagemap.h (diff)|
|parent||dma-buf/fence: fix fence_is_later v2 (diff)|
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')
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
@@ -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