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authorBorislav Petkov <bp@suse.de>2018-09-27 18:36:24 +0200
committerBorislav Petkov <bp@suse.de>2018-09-27 18:36:24 +0200
commitd913e8966a8f4b259dd6f11f0c334d865cf9d3aa (patch)
tree0b354028600f61001317426da875edc50685d36d /Documentation/i2c/DMA-considerations
parent6b58859419554fb824e09cfdd73151a195473cbc (diff)
parentc9661c1e80b609cd038db7c908e061f0535804ef (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-considerations10
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.