diff options
| author | Bjorn Helgaas <bhelgaas@google.com> | 2014-04-30 21:20:53 +0400 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2014-05-21 02:54:21 +0400 |
| commit | 77f2ea2f8d0833f9e976368481fb9a0775acf9e7 (patch) | |
| tree | 007a1fb1dcfa6f9cb0baa26548af80b90148fabd /include/linux | |
| parent | c9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff) | |
| download | linux-77f2ea2f8d0833f9e976368481fb9a0775acf9e7.tar.xz | |
DMA-API: Clarify physical/bus address distinction
The DMA-API documentation sometimes refers to "physical addresses" when it
really means "bus addresses." Sometimes these are identical, but they may
be different if the bridge leading to the bus performs address translation.
Update the documentation to use "bus address" when appropriate.
Also, consistently capitalize "DMA", use parens with function names, use
dev_printk() in examples, and reword a few sections for clarity.
No functional change; documentation changes only.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: James Bottomley <jbottomley@Parallels.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/dma-mapping.h | 6 | ||||
| -rw-r--r-- | include/linux/types.h | 1 |
2 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index fd4aee29ad10..b9aa2b97aab5 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -8,6 +8,12 @@ #include <linux/dma-direction.h> #include <linux/scatterlist.h> +/* + * A dma_addr_t can hold any valid DMA or bus address for the platform. + * It can be given to a device to use as a DMA source or target. A CPU cannot + * reference a dma_addr_t directly because there may be translation between + * its physical address space and the bus address space. + */ struct dma_map_ops { void* (*alloc)(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, diff --git a/include/linux/types.h b/include/linux/types.h index 4d118ba11349..a0bb7048687f 100644 --- a/include/linux/types.h +++ b/include/linux/types.h @@ -142,6 +142,7 @@ typedef unsigned long blkcnt_t; #define pgoff_t unsigned long #endif +/* A dma_addr_t can hold any valid DMA or bus address for the platform */ #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT typedef u64 dma_addr_t; #else |