From a9a62c9384417545620aee1b5ad1d9357350c17a Mon Sep 17 00:00:00 2001 From: Mauricio Faria de Oliveira Date: Tue, 11 Oct 2016 13:54:14 -0700 Subject: dma-mapping: introduce the DMA_ATTR_NO_WARN attribute 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 Cc: Keith Busch Cc: Jens Axboe Cc: Benjamin Herrenschmidt Cc: Michael Ellerman Cc: Krzysztof Kozlowski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/DMA-attributes.txt | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'Documentation') diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index 2d455a5cf671..98bf7ac29aad 100644 --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -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. -- cgit v1.2.3