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[PATCH v2 1/3] dma: introduce DMA_ATTR_NO_WARN

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Introduce the DMA_ATTR_NO_WARN attribute, and document it.

Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
---
Changelog:
 v2:
  - 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

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[PATCH v2 0/3] dma, nvme, powerpc: introduce and implement DMA_ATTR_NO_WARN Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> - 2016-07-07 14:50 +0200
  [PATCH v2 1/3] dma: introduce DMA_ATTR_NO_WARN Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> - 2016-07-07 14:50 +0200
  [PATCH v2 3/3] powerpc: implement DMA_ATTR_NO_WARN Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> - 2016-07-07 14:50 +0200
  [PATCH v2 2/3] nvme: implement DMA_ATTR_NO_WARN Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> - 2016-07-07 14:50 +0200
    Re: [PATCH v2 2/3] nvme: implement DMA_ATTR_NO_WARN Masayoshi Mizuma <m.mizuma@jp.fujitsu.com> - 2016-07-08 10:00 +0200
      Re: [PATCH v2 2/3] nvme: implement DMA_ATTR_NO_WARN Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com> - 2016-07-08 14:30 +0200

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