path: root/Documentation/DMA-API.txt
diff options
authorJohn Keller <jpk@sgi.com>2008-11-24 16:47:17 -0600
committerTony Luck <tony.luck@intel.com>2009-01-15 10:42:16 -0800
commit175add1981e53d22caba8f42d5f924a4de507b6c (patch)
tree71ddbf7f46d18222f4f5867d7261b335677c6af6 /Documentation/DMA-API.txt
parenta6a3bb5c88d706c5efe0c86b3b669ac9ee012b3f (diff)
[IA64] SN specific version of dma_get_required_mask()
Create a platform specific version of dma_get_required_mask() for ia64 SN Altix. All SN Altix platforms support 64 bit DMA addressing regardless of the size of system memory. Create an ia64 machvec for dma_get_required_mask, with the SN version unconditionally returning DMA_64BIT_MASK. Signed-off-by: John Keller <jpk@sgi.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
Diffstat (limited to 'Documentation/DMA-API.txt')
1 files changed, 4 insertions, 5 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index b462bb14954..52441694fe0 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -170,16 +170,15 @@ Returns: 0 if successful and a negative error if not.
dma_get_required_mask(struct device *dev)
-After setting the mask with dma_set_mask(), this API returns the
-actual mask (within that already set) that the platform actually
-requires to operate efficiently. Usually this means the returned mask
+This API returns the mask that the platform requires to
+operate efficiently. Usually this means the returned mask
is the minimum required to cover all of memory. Examining the
required mask gives drivers with variable descriptor sizes the
opportunity to use smaller descriptors as necessary.
Requesting the required mask does not alter the current mask. If you
-wish to take advantage of it, you should issue another dma_set_mask()
-call to lower the mask again.
+wish to take advantage of it, you should issue a dma_set_mask()
+call to set the mask to the value returned.
Part Id - Streaming DMA mappings