[v4,02/12] linux/types.h: Add dma_peer_addr_t type

Commit Message

[e-mail] July 22, 2015, 9:39 p.m. UTC

On some platforms, a dma_addr_t is only 32 bits wide, but the bus addresses
can be 64 bits wide. For peer-to-peer DMA, a device needs to use the full
64-bit address. Therefore, introduce a DMA address type that is not
constrained by the CPU DMA address size.

This is only needed for peer-to-peer DMA, so guard this definition with a
CONFIG_HAS_DMA_P2P check.

Signed-off-by: Will Davis <[e-mail]>
---
 include/linux/types.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Patch

diff --git a/include/linux/types.h b/include/linux/types.h
index 8715287..dd85173 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -140,13 +140,13 @@  typedef unsigned long blkcnt_t;
 #define pgoff_t unsigned long
 
 /*
- * A dma_addr_t can hold any valid DMA address, i.e., any address returned
+ * A dma_addr_t can hold any valid DMA address, i.e., most addresses returned
  * by the DMA API.
  *
  * If the DMA API only uses 32-bit addresses, dma_addr_t need only be 32
  * bits wide.  Bus addresses, e.g., PCI BARs, may be wider than 32 bits,
  * but drivers do memory-mapped I/O to ioremapped kernel virtual addresses,
- * so they don't care about the size of the actual bus addresses.
+ * so they don't care about the size of the actual bus addresses in most cases.
  */
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
 typedef u64 dma_addr_t;
@@ -154,6 +154,15 @@  typedef u64 dma_addr_t;
 typedef u32 dma_addr_t;
 #endif
 
+/*
+ * Unlike dma_addr_t, a dma_peer_addr_t can hold any bus address for the
+ * platform. Drivers should only need this for peer-to-peer use cases, where
+ * the DMA target is also on the bus.
+ */
+#ifdef CONFIG_HAS_DMA_P2P
+typedef u64 dma_peer_addr_t;
+#endif
+
 typedef unsigned __bitwise__ gfp_t;
 typedef unsigned __bitwise__ fmode_t;
 typedef unsigned __bitwise__ oom_flags_t;