diff options
Diffstat (limited to 'Documentation/DMA-API.txt')
| -rw-r--r-- | Documentation/DMA-API.txt | 69 |
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 ----------------------------- |