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authorDave Airlie <airlied@redhat.com>2012-05-22 13:34:38 +0100
committerSumit Semwal <sumit.semwal@ti.com>2012-05-25 12:51:11 +0530
commitb25b086d23eb852bf3cfdeb60409b4967ebb3c0c (patch)
treeb7c40775fe47606e319f1d2dab3842ad3460c316 /Documentation/dma-buf-sharing.txt
parent12c4727e1d5370270a7df781d2ba0a76e05c1137 (diff)
downloadlinux-aarch64-b25b086d23eb852bf3cfdeb60409b4967ebb3c0c.tar.gz
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.txt11
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,