diff options
| -rw-r--r-- | Documentation/DMA-API.txt | 58 | ||||
| -rw-r--r-- | include/linux/dma-mapping.h | 16 | ||||
| -rw-r--r-- | include/linux/pci-dma.h | 21 |
3 files changed, 80 insertions, 15 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 364a6cb444a5..29a48fbae779 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -472,6 +472,64 @@ void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr, .... +Part Ie - Optimizing Unmap State Space Consumption +-------------------------------- + +On some platforms, dma_unmap_{single,page}() is simply a nop. +Therefore, keeping track of the mapping address and length is a waste +of space. Instead of filling your drivers up with ifdefs and the like +to "work around" this (which would defeat the whole purpose of a +portable API) the following facilities are provided. + +Actually, instead of describing the macros one by one, we'll +transform some example code. + +1) Use DEFINE_DMA_UNMAP_{ADDR,LEN} in state saving structures. + Example, before: + + struct ring_state { + struct sk_buff *skb; + dma_addr_t mapping; + __u32 len; + }; + + after: + + struct ring_state { + struct sk_buff *skb; + DEFINE_DMA_UNMAP_ADDR(mapping); + DEFINE_DMA_UNMAP_LEN(len); + }; + +2) Use dma_unmap_{addr,len}_set to set these values. + Example, before: + + ringp->mapping = FOO; + ringp->len = BAR; + + after: + + dma_unmap_addr_set(ringp, mapping, FOO); + dma_unmap_len_set(ringp, len, BAR); + +3) Use dma_unmap_{addr,len} to access these values. + Example, before: + + dma_unmap_single(dev, ringp->mapping, ringp->len, + DMA_FROM_DEVICE); + + after: + + dma_unmap_single(dev, + dma_unmap_addr(ringp, mapping), + dma_unmap_len(ringp, len), + DMA_FROM_DEVICE); + +It really should be self-explanatory. We treat the ADDR and LEN +separately, because it is possible for an implementation to only +need the address in order to perform the unmap operation. + + Part II - Advanced dma_ usage ----------------------------- diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 91b761846061..c5ac9d49cc06 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -232,4 +232,20 @@ struct dma_attrs; #endif /* CONFIG_HAVE_DMA_ATTRS */ +#ifdef CONFIG_NEED_DMA_MAP_STATE +#define DEFINE_DMA_UNMAP_ADDR(ADDR_NAME) dma_addr_t ADDR_NAME +#define DEFINE_DMA_UNMAP_LEN(LEN_NAME) __u32 LEN_NAME +#define dma_unmap_addr(PTR, ADDR_NAME) ((PTR)->ADDR_NAME) +#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL) (((PTR)->ADDR_NAME) = (VAL)) +#define dma_unmap_len(PTR, LEN_NAME) ((PTR)->LEN_NAME) +#define dma_unmap_len_set(PTR, LEN_NAME, VAL) (((PTR)->LEN_NAME) = (VAL)) +#else +#define DEFINE_DMA_UNMAP_ADDR(ADDR_NAME) +#define DEFINE_DMA_UNMAP_LEN(LEN_NAME) +#define dma_unmap_addr(PTR, ADDR_NAME) (0) +#define dma_unmap_addr_set(PTR, ADDR_NAME, VAL) do { } while (0) +#define dma_unmap_len(PTR, LEN_NAME) (0) +#define dma_unmap_len_set(PTR, LEN_NAME, VAL) do { } while (0) +#endif + #endif diff --git a/include/linux/pci-dma.h b/include/linux/pci-dma.h index cfd63ab09abc..549a041f9c08 100644 --- a/include/linux/pci-dma.h +++ b/include/linux/pci-dma.h @@ -1,20 +1,11 @@ #ifndef _LINUX_PCI_DMA_H #define _LINUX_PCI_DMA_H -#ifdef CONFIG_NEED_DMA_MAP_STATE -#define DECLARE_PCI_UNMAP_ADDR(ADDR_NAME) dma_addr_t ADDR_NAME; -#define DECLARE_PCI_UNMAP_LEN(LEN_NAME) __u32 LEN_NAME; -#define pci_unmap_addr(PTR, ADDR_NAME) ((PTR)->ADDR_NAME) -#define pci_unmap_addr_set(PTR, ADDR_NAME, VAL) (((PTR)->ADDR_NAME) = (VAL)) -#define pci_unmap_len(PTR, LEN_NAME) ((PTR)->LEN_NAME) -#define pci_unmap_len_set(PTR, LEN_NAME, VAL) (((PTR)->LEN_NAME) = (VAL)) -#else -#define DECLARE_PCI_UNMAP_ADDR(ADDR_NAME) -#define DECLARE_PCI_UNMAP_LEN(LEN_NAME) -#define pci_unmap_addr(PTR, ADDR_NAME) (0) -#define pci_unmap_addr_set(PTR, ADDR_NAME, VAL) do { } while (0) -#define pci_unmap_len(PTR, LEN_NAME) (0) -#define pci_unmap_len_set(PTR, LEN_NAME, VAL) do { } while (0) -#endif +#define DECLARE_PCI_UNMAP_ADDR(ADDR_NAME) DEFINE_DMA_UNMAP_ADDR(ADDR_NAME); +#define DECLARE_PCI_UNMAP_LEN(LEN_NAME) DEFINE_DMA_UNMAP_LEN(LEN_NAME); +#define pci_unmap_addr dma_unmap_addr +#define pci_unmap_addr_set dma_unmap_addr_set +#define pci_unmap_len dma_unmap_len +#define pci_unmap_len_set dma_unmap_len_set #endif |