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Commit 0acedc12 authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Linus Torvalds
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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: default avatarFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: James Bottomley <James.Bottomley@suse.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f41b1771

Documentation/DMA-API.txt

+58 −0
Original line number Diff line number Diff line
@@ -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

-----------------------------

include/linux/dma-mapping.h

+16 −0
Original line number Diff line number Diff line
@@ -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

include/linux/pci-dma.h

+6 −15
Original line number Diff line number Diff line 
#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