diff options
Diffstat (limited to 'Documentation/dma-buf-sharing.txt')
-rw-r--r-- | Documentation/dma-buf-sharing.txt | 19 |
1 files changed, 8 insertions, 11 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index 480c8de3c2c4..4f4a84b6903a 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -257,17 +257,15 @@ Access to a dma_buf from the kernel context involves three steps: Interface: int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, - size_t start, size_t len, enum dma_data_direction direction) This allows the exporter to ensure that the memory is actually available for cpu access - the exporter might need to allocate or swap-in and pin the backing storage. The exporter also needs to ensure that cpu access is - coherent for the given range and access direction. The range and access - direction can be used by the exporter to optimize the cache flushing, i.e. - access outside of the range or with a different direction (read instead of - write) might return stale or even bogus data (e.g. when the exporter needs to - copy the data to temporary storage). + coherent for the access direction. The direction can be used by the exporter + to optimize the cache flushing, i.e. access with a different direction (read + instead of write) might return stale or even bogus data (e.g. when the + exporter needs to copy the data to temporary storage). This step might fail, e.g. in oom conditions. @@ -322,14 +320,13 @@ Access to a dma_buf from the kernel context involves three steps: 3. Finish access - When the importer is done accessing the range specified in begin_cpu_access, - it needs to announce this to the exporter (to facilitate cache flushing and - unpinning of any pinned resources). The result of any dma_buf kmap calls - after end_cpu_access is undefined. + When the importer is done accessing the CPU, it needs to announce this to + the exporter (to facilitate cache flushing and unpinning of any pinned + resources). The result of any dma_buf kmap calls after end_cpu_access is + undefined. Interface: void dma_buf_end_cpu_access(struct dma_buf *dma_buf, - size_t start, size_t len, enum dma_data_direction dir); |