Hi
On Mon, Mar 21, 2016 at 8:51 AM, Daniel Vetter daniel.vetter@ffwll.ch wrote:
Just a bit of wording polish plus mentioning that it can fail and must be restarted.
Requested by Sumit.
v2: Fix them typos (Hans).
Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Tiago Vignatti tiago.vignatti@intel.com Cc: Stéphane Marchesin marcheu@chromium.org Cc: David Herrmann dh.herrmann@gmail.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Daniel Vetter daniel.vetter@intel.com CC: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Cc: intel-gfx@lists.freedesktop.org Cc: devel@driverdev.osuosl.org Cc: Hans Verkuil hverkuil@xs4all.nl Acked-by: Sumit Semwal sumit.semwal@linaro.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com
Documentation/dma-buf-sharing.txt | 11 ++++++----- drivers/dma-buf/dma-buf.c | 2 +- 2 files changed, 7 insertions(+), 6 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.
What is "restart on EAGAIN" supposed to mean? Or more generally, what does EAGAIN tell the caller?
Thanks David
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.
- Supporting existing mmap interfaces in importers
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 774a60f4309a..4a2c07ee6677 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -612,7 +612,7 @@ EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
- @dmabuf: [in] buffer to complete cpu access for.
- @direction: [in] length of range for cpu access.
- This call must always succeed.
*/
- Can return negative error values, returns 0 on success.
int dma_buf_end_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction) -- 2.8.0.rc3