diff options
Diffstat (limited to 'Documentation/i2c')
| -rw-r--r-- | Documentation/i2c/DMA-considerations | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/i2c/DMA-considerations b/Documentation/i2c/DMA-considerations index 966610aa4620..203002054120 100644 --- a/Documentation/i2c/DMA-considerations +++ b/Documentation/i2c/DMA-considerations @@ -50,10 +50,14 @@ bounce buffer. But you don't need to care about that detail, just use the returned buffer. If NULL is returned, the threshold was not met or a bounce buffer could not be allocated. Fall back to PIO in that case. -In any case, a buffer obtained from above needs to be released. It ensures data -is copied back to the message and a potentially used bounce buffer is freed:: +In any case, a buffer obtained from above needs to be released. Another helper +function ensures a potentially used bounce buffer is freed:: - i2c_release_dma_safe_msg_buf(msg, dma_buf); + i2c_put_dma_safe_msg_buf(dma_buf, msg, xferred); + +The last argument 'xferred' controls if the buffer is synced back to the +message or not. No syncing is needed in cases setting up DMA had an error and +there was no data transferred. The bounce buffer handling from the core is generic and simple. It will always allocate a new bounce buffer. If you want a more sophisticated handling (e.g. |