On 03/21/2016 04:51 AM, Daniel Vetter 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 at chris-wilson.co.uk> > Cc: Tiago Vignatti <tiago.vignatti at intel.com> > Cc: Stéphane Marchesin <marcheu at chromium.org> > Cc: David Herrmann <dh.herrmann at gmail.com> > Cc: Sumit Semwal <sumit.semwal at linaro.org> > Cc: Daniel Vetter <daniel.vetter at intel.com> > CC: linux-media at vger.kernel.org > Cc: dri-devel at lists.freedesktop.org > Cc: linaro-mm-sig at lists.linaro.org > Cc: intel-gfx at lists.freedesktop.org > Cc: devel at driverdev.osuosl.org > Cc: Hans Verkuil <hverkuil at xs4all.nl> > Acked-by: Sumit Semwal <sumit.semwal at linaro.org> > Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Reviewed-by: Tiago Vignatti <tiago.vignatti at intel.com> Best regards, Tiago > --- > 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. > > 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 > > 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) >
