summaryrefslogtreecommitdiff
path: root/Documentation/DMA-API.txt
diff options
context:
space:
mode:
authorSteve French <sfrench@us.ibm.com>2008-05-06 17:55:32 +0000
committerSteve French <sfrench@us.ibm.com>2008-05-06 17:55:32 +0000
commita815752ac0ffdb910e92958d41d28f4fb28e5296 (patch)
treea3aa16a282354da0debe8e3a3a7ed8aac6e54001 /Documentation/DMA-API.txt
parent5ade9deaaa3e1f7291467d97b238648e43eae15e (diff)
parenta15306365a16380f3bafee9e181ba01231d4acd7 (diff)
Merge branch 'master' of /pub/scm/linux/kernel/git/torvalds/linux-2.6
Diffstat (limited to 'Documentation/DMA-API.txt')
-rw-r--r--Documentation/DMA-API.txt69
1 files changed, 67 insertions, 2 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index b939ebb62871..80d150458c80 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -145,7 +145,7 @@ Part Ic - DMA addressing limitations
int
dma_supported(struct device *dev, u64 mask)
int
-pci_dma_supported(struct device *dev, u64 mask)
+pci_dma_supported(struct pci_dev *hwdev, u64 mask)
Checks to see if the device can support DMA to the memory described by
mask.
@@ -189,7 +189,7 @@ dma_addr_t
dma_map_single(struct device *dev, void *cpu_addr, size_t size,
enum dma_data_direction direction)
dma_addr_t
-pci_map_single(struct device *dev, void *cpu_addr, size_t size,
+pci_map_single(struct pci_dev *hwdev, void *cpu_addr, size_t size,
int direction)
Maps a piece of processor virtual memory so it can be accessed by the
@@ -395,6 +395,71 @@ Notes: You must do this:
See also dma_map_single().
+dma_addr_t
+dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size,
+ enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+
+void
+dma_unmap_single_attrs(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+
+int
+dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+
+void
+dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+
+The four functions above are just like the counterpart functions
+without the _attrs suffixes, except that they pass an optional
+struct dma_attrs*.
+
+struct dma_attrs encapsulates a set of "dma attributes". For the
+definition of struct dma_attrs see linux/dma-attrs.h.
+
+The interpretation of dma attributes is architecture-specific, and
+each attribute should be documented in Documentation/DMA-attributes.txt.
+
+If struct dma_attrs* is NULL, the semantics of each of these
+functions is identical to those of the corresponding function
+without the _attrs suffix. As a result dma_map_single_attrs()
+can generally replace dma_map_single(), etc.
+
+As an example of the use of the *_attrs functions, here's how
+you could pass an attribute DMA_ATTR_FOO when mapping memory
+for DMA:
+
+#include <linux/dma-attrs.h>
+/* DMA_ATTR_FOO should be defined in linux/dma-attrs.h and
+ * documented in Documentation/DMA-attributes.txt */
+...
+
+ DEFINE_DMA_ATTRS(attrs);
+ dma_set_attr(DMA_ATTR_FOO, &attrs);
+ ....
+ n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, &attr);
+ ....
+
+Architectures that care about DMA_ATTR_FOO would check for its
+presence in their implementations of the mapping and unmapping
+routines, e.g.:
+
+void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ struct dma_attrs *attrs)
+{
+ ....
+ int foo = dma_get_attr(DMA_ATTR_FOO, attrs);
+ ....
+ if (foo)
+ /* twizzle the frobnozzle */
+ ....
+
Part II - Advanced dma_ usage
-----------------------------