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author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-15 22:58:58 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-07-15 22:58:58 +0300 |
commit | 486088bc4689f826b80aa317b45ac9e42e8b25ee (patch) | |
tree | adf5847a6119d24da990d9e336f005c4a316e6be /Documentation/DMA-attributes.txt | |
parent | 52f6c588c77b76d548201470c2a28263a41b462b (diff) | |
parent | 43e5f7e1fa66531777c49791014c3124ea9208d8 (diff) | |
download | linux-486088bc4689f826b80aa317b45ac9e42e8b25ee.tar.xz |
Merge tag 'standardize-docs' of git://git.lwn.net/linux
Pull documentation format standardization from Jonathan Corbet:
"This series converts a number of top-level documents to the RST format
without incorporating them into the Sphinx tree. The hope is to bring
some uniformity to kernel documentation and, perhaps more importantly,
have our existing docs serve as an example of the desired formatting
for those that will be added later.
Mauro has gone through and fixed up a lot of top-level documentation
files to make them conform to the RST format, but without moving or
renaming them in any way. This will help when we incorporate the ones
we want to keep into the Sphinx doctree, but the real purpose is to
bring a bit of uniformity to our documentation and let the top-level
docs serve as examples for those writing new ones"
* tag 'standardize-docs' of git://git.lwn.net/linux: (84 commits)
docs: kprobes.txt: Fix whitespacing
tee.txt: standardize document format
cgroup-v2.txt: standardize document format
dell_rbu.txt: standardize document format
zorro.txt: standardize document format
xz.txt: standardize document format
xillybus.txt: standardize document format
vfio.txt: standardize document format
vfio-mediated-device.txt: standardize document format
unaligned-memory-access.txt: standardize document format
this_cpu_ops.txt: standardize document format
svga.txt: standardize document format
static-keys.txt: standardize document format
smsc_ece1099.txt: standardize document format
SM501.txt: standardize document format
siphash.txt: standardize document format
sgi-ioc4.txt: standardize document format
SAK.txt: standardize document format
rpmsg.txt: standardize document format
robust-futexes.txt: standardize document format
...
Diffstat (limited to 'Documentation/DMA-attributes.txt')
-rw-r--r-- | Documentation/DMA-attributes.txt | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index 44c6bc496eee..8f8d97f65d73 100644 --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -1,5 +1,6 @@ - DMA attributes - ============== +============== +DMA attributes +============== This document describes the semantics of the DMA attributes that are defined in linux/dma-mapping.h. @@ -108,6 +109,7 @@ This is a hint to the DMA-mapping subsystem that it's probably not worth the time to try to allocate memory to in a way that gives better TLB efficiency (AKA it's not worth trying to build the mapping out of larger pages). You might want to specify this if: + - You know that the accesses to this memory won't thrash the TLB. You might know that the accesses are likely to be sequential or that they aren't sequential but it's unlikely you'll ping-pong @@ -121,11 +123,12 @@ pages). You might want to specify this if: the mapping to have a short lifetime then it may be worth it to optimize allocation (avoid coming up with large pages) instead of getting the slight performance win of larger pages. + Setting this hint doesn't guarantee that you won't get huge pages, but it 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. +.. 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 ---------------- @@ -142,10 +145,10 @@ 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. +.. note:: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC. DMA_ATTR_PRIVILEGED ------------------------------- +------------------- Some advanced peripherals such as remote processors and GPUs perform accesses to DMA buffers in both privileged "supervisor" and unprivileged |