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| author | Christoph Hellwig <hch@lst.de> | 2019-11-13 08:32:13 +0100 |
|---|---|---|
| committer | Jason Gunthorpe <jgg@mellanox.com> | 2019-11-14 12:01:54 -0400 |
| commit | 7283fff8b524b2f27438429aca458b232f5c5c8a (patch) | |
| tree | ff5f32d6c4ed5968d8c7df5a2d8707d579d43baf /Documentation/DMA-attributes.txt | |
| parent | 64c264872b8879e2ab9017eefe9514d4c045c60e (diff) | |
| download | lwn-7283fff8b524b2f27438429aca458b232f5c5c8a.tar.gz lwn-7283fff8b524b2f27438429aca458b232f5c5c8a.zip | |
dma-mapping: remove the DMA_ATTR_WRITE_BARRIER flag
This flag is not implemented by any backend and only set by the ib_umem
module in a single instance.
Link: https://lore.kernel.org/r/20191113073214.9514-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'Documentation/DMA-attributes.txt')
| -rw-r--r-- | Documentation/DMA-attributes.txt | 18 |
1 files changed, 0 insertions, 18 deletions
diff --git a/Documentation/DMA-attributes.txt b/Documentation/DMA-attributes.txt index 8f8d97f65d73..29dcbe8826e8 100644 --- a/Documentation/DMA-attributes.txt +++ b/Documentation/DMA-attributes.txt @@ -5,24 +5,6 @@ DMA attributes This document describes the semantics of the DMA attributes that are defined in linux/dma-mapping.h. -DMA_ATTR_WRITE_BARRIER ----------------------- - -DMA_ATTR_WRITE_BARRIER is a (write) barrier attribute for DMA. DMA -to a memory region with the DMA_ATTR_WRITE_BARRIER attribute forces -all pending DMA writes to complete, and thus provides a mechanism to -strictly order DMA from a device across all intervening busses and -bridges. This barrier is not specific to a particular type of -interconnect, it applies to the system as a whole, and so its -implementation must account for the idiosyncrasies of the system all -the way from the DMA device to memory. - -As an example of a situation where DMA_ATTR_WRITE_BARRIER would be -useful, suppose that a device does a DMA write to indicate that data is -ready and available in memory. The DMA of the "completion indication" -could race with data DMA. Mapping the memory used for completion -indications with DMA_ATTR_WRITE_BARRIER would prevent the race. - DMA_ATTR_WEAK_ORDERING ---------------------- |