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author | Borislav Petkov <bp@suse.de> | 2018-09-27 18:36:24 +0200 |
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committer | Borislav Petkov <bp@suse.de> | 2018-09-27 18:36:24 +0200 |
commit | d913e8966a8f4b259dd6f11f0c334d865cf9d3aa (patch) | |
tree | 0b354028600f61001317426da875edc50685d36d /Documentation/i2c/DMA-considerations | |
parent | 6b58859419554fb824e09cfdd73151a195473cbc (diff) | |
parent | c9661c1e80b609cd038db7c908e061f0535804ef (diff) |
Merge branch 'tip-x86-hygon' into edac-for-4.20
... to pick up a dependent commit and share it with the tip tree, branch
tip:x86/cpu.
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'Documentation/i2c/DMA-considerations')
-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. |