path: root/Documentation/DMA-ISA-LPC.txt
diff options
authorBjorn Helgaas <>2014-04-30 11:20:53 -0600
committerBjorn Helgaas <>2014-05-20 16:54:21 -0600
commit77f2ea2f8d0833f9e976368481fb9a0775acf9e7 (patch)
tree007a1fb1dcfa6f9cb0baa26548af80b90148fabd /Documentation/DMA-ISA-LPC.txt
parentc9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff)
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 <> Acked-by: Greg Kroah-Hartman <> Acked-by: Arnd Bergmann <> Acked-by: James Bottomley <> Acked-by: Randy Dunlap <>
Diffstat (limited to 'Documentation/DMA-ISA-LPC.txt')
1 files changed, 2 insertions, 2 deletions
diff --git a/Documentation/DMA-ISA-LPC.txt b/Documentation/DMA-ISA-LPC.txt
index e767805b4182..b1a19835e907 100644
--- a/Documentation/DMA-ISA-LPC.txt
+++ b/Documentation/DMA-ISA-LPC.txt
@@ -16,7 +16,7 @@ To do ISA style DMA you need to include two headers:
#include <asm/dma.h>
The first is the generic DMA API used to convert virtual addresses to
-physical addresses (see Documentation/DMA-API.txt for details).
+bus addresses (see Documentation/DMA-API.txt for details).
The second contains the routines specific to ISA DMA transfers. Since
this is not present on all platforms make sure you construct your
@@ -50,7 +50,7 @@ early as possible and not release it until the driver is unloaded.)
Part III - Address translation
-To translate the virtual address to a physical use the normal DMA
+To translate the virtual address to a bus address, use the normal DMA
API. Do _not_ use isa_virt_to_phys() even though it does the same
thing. The reason for this is that the function isa_virt_to_phys()
will require a Kconfig dependency to ISA, not just ISA_DMA_API which