Commit a9a62c93 authored by Mauricio Faria de Oliveira's avatar Mauricio Faria de Oliveira Committed by Linus Torvalds

dma-mapping: introduce the DMA_ATTR_NO_WARN attribute

Introduce the DMA_ATTR_NO_WARN attribute, and document it.

Link: default avatarMauricio Faria de Oliveira <>
Cc: Keith Busch <>
Cc: Jens Axboe <>
Cc: Benjamin Herrenschmidt <>
Cc: Michael Ellerman <>
Cc: Krzysztof Kozlowski <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 7425154d
......@@ -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.
......@@ -56,6 +56,11 @@
* that gives better TLB efficiency.
* 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.
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