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Date: Fri, 12 Feb 2010 15:04:52 +0900 From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> To: linux-kernel@...r.kernel.org Cc: akpm@...ux-foundation.org, James.Bottomley@...e.de, davem@...emloft.net, jbarnes@...tuousgeek.org, arnd@...db.de Subject: [PATCH -mm] dma-mapping.h: add the dma_unmap state API Adds the following macros: DECLARE_DMA_UNMAP_ADDR(ADDR_NAME) DECLARE_DMA_UNMAP_LEN(LEN_NAME) dma_unmap_addr(PTR, ADDR_NAME) dma_unmap_addr_set(PTR, ADDR_NAME, VAL) dma_unmap_len(PTR, LEN_NAME) dma_unmap_len_set(PTR, LEN_NAME, VAL) The API corresponds to the pci_unmap state API. We'll move to this new generic API from the PCI specific API in the long term. As include/asm-generic/pci-dma-compat.h does, the pci_unmap API simply calls the new generic API for some time. Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> Cc: James Bottomley <James.Bottomley@...e.de> Cc: David S. Miller <davem@...emloft.net> Cc: Jesse Barnes <jbarnes@...tuousgeek.org> Cc: Arnd Bergmann <arnd@...db.de> --- Documentation/DMA-API.txt | 60 +++++++++++++++++++++++++++++++++++++++++++ include/linux/dma-mapping.h | 16 +++++++++++ include/linux/pci-dma.h | 21 ++++---------- 3 files changed, 82 insertions(+), 15 deletions(-) diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 364a6cb..bd34a62 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -472,6 +472,66 @@ 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 DECLARE_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; + DECLARE_DMA_UNMAP_ADDR(mapping) + DECLARE_DMA_UNMAP_LEN(len) + }; + +NOTE: DO NOT put a semicolon at the end of the DECLARE_*() macro. + +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 91b7618..86e7dc3 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 DECLARE_DMA_UNMAP_ADDR(ADDR_NAME) dma_addr_t ADDR_NAME; +#define DECLARE_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 DECLARE_DMA_MAP_ADDR(ADDR_NAME) +#define DECLARE_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 cfd63ab..235a61e 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 DECLARE_DMA_UNMAP_ADDR +#define DECLARE_PCI_UNMAP_LEN DECLARE_DMA_UNMAP_LEN +#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 -- 1.5.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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