From mboxrd@z Thu Jan 1 00:00:00 1970 From: mauricfo@linux.vnet.ibm.com (Mauricio Faria de Oliveira) Date: Fri, 8 Jul 2016 09:27:06 -0300 Subject: [PATCH v3 1/3] dma: introduce DMA_ATTR_NO_WARN In-Reply-To: <1467980828-5282-1-git-send-email-mauricfo@linux.vnet.ibm.com> References: <1467980828-5282-1-git-send-email-mauricfo@linux.vnet.ibm.com> Message-ID: <1467980828-5282-2-git-send-email-mauricfo@linux.vnet.ibm.com> Introduce the DMA_ATTR_NO_WARN attribute, and document it. Signed-off-by: Mauricio Faria de Oliveira --- Changelog: v3: - dma: none. v2: - all: address warnings from checkpatch.pl (line wrapping and typos) Documentation/DMA-attributes.txt | 17 +++++++++++++++++ include/linux/dma-attrs.h | 1 + 2 files changed, 18 insertions(+) diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index e8cf9cf..48150c6 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. diff --git a/include/linux/dma-attrs.h b/include/linux/dma-attrs.h index f3c5aea..0577389 100644 --- a/include/linux/dma-attrs.h +++ b/include/linux/dma-attrs.h @@ -19,6 +19,7 @@ enum dma_attr { DMA_ATTR_SKIP_CPU_SYNC, DMA_ATTR_FORCE_CONTIGUOUS, DMA_ATTR_ALLOC_SINGLE_PAGES, + DMA_ATTR_NO_WARN, DMA_ATTR_MAX, }; -- 1.8.3.1