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authorLinus Torvalds <torvalds@linux-foundation.org>2018-08-31 08:38:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-31 08:38:53 -0700
commit754cf4b2432dfea0f925a0b760506a9c97c8f00b (patch)
tree67f7d6006068de60336c7ae051af9c512ba2e489 /Documentation
parent4658aff6eeaaf0b049ce787513abfc985c452e3a (diff)
parentcebc07d84ad71bc58d6f59b770e4347da48a5a2b (diff)
downloadlinux-754cf4b2432dfea0f925a0b760506a9c97c8f00b.tar.bz2
Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c fixes from Wolfram Sang: - regression fixes for i801 and designware - better API and leak fix for releasing DMA safe buffers - better greppable strings for the bitbang algorithm * 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux: i2c: sh_mobile: fix leak when using DMA bounce buffer i2c: sh_mobile: define start_ch() void as it only returns 0 anyhow i2c: refactor function to release a DMA safe buffer i2c: algos: bit: make the error messages grepable i2c: designware: Re-init controllers with pm_disabled set on resume i2c: i801: Allow ACPI AML access I/O ports not reserved for SMBus
Diffstat (limited to 'Documentation')
-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.