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| author | Dave Airlie <airlied@redhat.com> | 2012-05-22 13:34:38 +0100 |
|---|---|---|
| committer | Sumit Semwal <sumit.semwal@ti.com> | 2012-05-25 12:51:11 +0530 |
| commit | b25b086d23eb852bf3cfdeb60409b4967ebb3c0c (patch) | |
| tree | b7c40775fe47606e319f1d2dab3842ad3460c316 /Documentation/dma-buf-sharing.txt | |
| parent | 12c4727e1d5370270a7df781d2ba0a76e05c1137 (diff) | |
| download | lwn-b25b086d23eb852bf3cfdeb60409b4967ebb3c0c.tar.gz lwn-b25b086d23eb852bf3cfdeb60409b4967ebb3c0c.zip | |
dma-buf: add initial vmap documentation
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Diffstat (limited to 'Documentation/dma-buf-sharing.txt')
| -rw-r--r-- | Documentation/dma-buf-sharing.txt | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 5ff4d2b84f72..ad86fb86c9a0 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -293,6 +293,17 @@ Access to a dma_buf from the kernel context involves three steps: Note that these calls need to always succeed. The exporter needs to complete any preparations that might fail in begin_cpu_access. + For some cases the overhead of kmap can be too high, a vmap interface + is introduced. This interface should be used very carefully, as vmalloc + space is a limited resources on many architectures. + + Interfaces: + void *dma_buf_vmap(struct dma_buf *dmabuf) + void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr) + + The vmap call can fail if there is no vmap support in the exporter, or if it + runs out of vmalloc space. Fallback to kmap should be implemented. + 3. Finish access When the importer is done accessing the range specified in begin_cpu_access, |