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author | Linus Torvalds <torvalds@linux-foundation.org> | 2018-08-31 18:38:53 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-08-31 18:38:53 +0300 |
commit | 754cf4b2432dfea0f925a0b760506a9c97c8f00b (patch) | |
tree | 67f7d6006068de60336c7ae051af9c512ba2e489 /Documentation | |
parent | 4658aff6eeaaf0b049ce787513abfc985c452e3a (diff) | |
parent | cebc07d84ad71bc58d6f59b770e4347da48a5a2b (diff) |
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-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. |