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authorChristoph Hellwig <hch@lst.de>2019-11-13 10:32:13 +0300
committerJason Gunthorpe <jgg@mellanox.com>2019-11-14 19:01:54 +0300
commit7283fff8b524b2f27438429aca458b232f5c5c8a (patch)
treeff5f32d6c4ed5968d8c7df5a2d8707d579d43baf /Documentation/DMA-attributes.txt
parent64c264872b8879e2ab9017eefe9514d4c045c60e (diff)
downloadlinux-7283fff8b524b2f27438429aca458b232f5c5c8a.tar.xz
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.txt18
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
----------------------