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dma-mapping: introduce the DMA_ATTR_NO_WARN attribute

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Introduce the DMA_ATTR_NO_WARN attribute, and document it.

Link: http://lkml.kernel.org/r/1470092390-25451-2-git-send-email-mauricfo@linux.vnet.ibm.com
Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mauricio Faria de Oliveira 2016-10-11 13:54:14 -07:00 committed by Linus Torvalds
parent 7425154d3b
commit a9a62c9384
2 changed files with 22 additions and 0 deletions
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17
Documentation/DMA-attributes.txt
View file

@ -126,3 +126,20 @@ means that we won't try quite as hard to get them.
NOTE: At the moment DMA_ATTR_ALLOC_SINGLE_PAGES is only implemented on ARM,
though ARM64 patches will likely be posted soon.
DMA_ATTR_NO_WARN
----------------
This tells the DMA-mapping subsystem to suppress allocation failure reports
(similarly to __GFP_NOWARN).
On some architectures allocation failures are reported with error messages
to the system logs. Although this can help to identify and debug problems,
drivers which handle failures (eg, retry later) have no problems with them,
and can actually flood the system logs with error messages that aren't any
problem at all, depending on the implementation of the retry mechanism.
So, this provides a way for drivers to avoid those error messages on calls
where allocation failures are not a problem, and shouldn't bother the logs.
NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC.

5
include/linux/dma-mapping.h
View file

@ -56,6 +56,11 @@
* that gives better TLB efficiency.
*/
#define DMA_ATTR_ALLOC_SINGLE_PAGES (1UL << 7)
/*
* DMA_ATTR_NO_WARN: This tells the DMA-mapping subsystem to suppress
* allocation failure reports (similarly to __GFP_NOWARN).
*/
#define DMA_ATTR_NO_WARN (1UL << 8)
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform.