The patch titled dma: document dma_*map*_attrs() interfaces has been removed from the -mm tree. Its filename was dma-document-dma_map_attrs-interfaces.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: dma: document dma_*map*_attrs() interfaces From: Arthur Kepner <akepner@xxxxxxx> Document the new dma_*map*_attrs() functions. [markn@xxxxxxxxxxx: fix up for dma-add-dma_map_attrs-interfaces and update docs] Signed-off-by: Arthur Kepner <akepner@xxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> Cc: Jes Sorensen <jes@xxxxxxx> Cc: Randy Dunlap <randy.dunlap@xxxxxxxxxx> Cc: Roland Dreier <rdreier@xxxxxxxxx> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Grant Grundler <grundler@xxxxxxxxxxxxxxxx> Cc: Michael Ellerman <michael@xxxxxxxxxxxxxx> Signed-off-by: Mark Nelson <markn@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/DMA-API.txt | 65 +++++++++++++++++++++++++++++ Documentation/DMA-attributes.txt | 24 ++++++++++ 2 files changed, 89 insertions(+) diff -puN Documentation/DMA-API.txt~dma-document-dma_map_attrs-interfaces Documentation/DMA-API.txt --- a/Documentation/DMA-API.txt~dma-document-dma_map_attrs-interfaces +++ a/Documentation/DMA-API.txt @@ -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 ----------------------------- diff -puN Documentation/DMA-attributes.txt~dma-document-dma_map_attrs-interfaces Documentation/DMA-attributes.txt --- a/Documentation/DMA-attributes.txt~dma-document-dma_map_attrs-interfaces +++ a/Documentation/DMA-attributes.txt @@ -0,0 +1,24 @@ + DMA attributes + ============== + +This document describes the semantics of the DMA attributes that are +defined in linux/dma-attrs.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 idiosyncracies 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. + _ Patches currently in -mm which might be from akepner@xxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html