[PATCH -mm] dma-mapping.h: add the dma_unmap state API
From: FUJITA Tomonori
Date: Fri Feb 12 2010 - 01:05:25 EST
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@xxxxxxxxxxxxx>
Cc: James Bottomley <James.Bottomley@xxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
---
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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