[PATCH v3 1/3] dma: introduce DMA_ATTR_NO_WARN

From: Mauricio Faria de Oliveira
Date: Fri Jul 08 2016 - 08:27:45 EST

Introduce the DMA_ATTR_NO_WARN attribute, and document it.

Signed-off-by: Mauricio Faria de Oliveira <mauricfo@xxxxxxxxxxxxxxxxxx>
- dma: none.
- 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.
+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 {