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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

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