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author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2016-12-09 22:50:55 +0100 |
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committer | Sumit Semwal <sumit.semwal@linaro.org> | 2016-12-13 17:54:28 +0530 |
commit | e7e21c72b178e963f3c990cb839d86f568999916 (patch) | |
tree | 80698d8bc3a5c3952e498ca0ef3e764c6ccff3c9 /drivers/dma-buf/dma-buf.c | |
parent | 0959a1683d78270bab6381d498707fb8655ae11c (diff) | |
download | op-kernel-dev-e7e21c72b178e963f3c990cb839d86f568999916.zip op-kernel-dev-e7e21c72b178e963f3c990cb839d86f568999916.tar.gz |
dma-buf: Final bits of doc polish
- Put all the remaing bits of the old doc into suitable places in the
new sphinx world.
- Also document the poll support, we forgot to do that.
- Delete dma-buf-sharing.txt.
v2: Don't forget to update MAINTAINERS.
Cc: linux-doc@vger.kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20161209215055.3492-1-daniel.vetter@ffwll.ch
Diffstat (limited to 'drivers/dma-buf/dma-buf.c')
-rw-r--r-- | drivers/dma-buf/dma-buf.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index eae0846..91aff74 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -124,6 +124,28 @@ static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) return base + offset; } +/** + * DOC: fence polling + * + * To support cross-device and cross-driver synchronization of buffer access + * implicit fences (represented internally in the kernel with struct &fence) can + * be attached to a &dma_buf. The glue for that and a few related things are + * provided in the &reservation_object structure. + * + * Userspace can query the state of these implicitly tracked fences using poll() + * and related system calls: + * + * - Checking for POLLIN, i.e. read access, can be use to query the state of the + * most recent write or exclusive fence. + * + * - Checking for POLLOUT, i.e. write access, can be used to query the state of + * all attached fences, shared and exclusive ones. + * + * Note that this only signals the completion of the respective fences, i.e. the + * DMA transfers are complete. Cache flushing and any other necessary + * preparations before CPU access can begin still need to happen. + */ + static void dma_buf_poll_cb(struct dma_fence *fence, struct dma_fence_cb *cb) { struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb; |