Merge branch 'master'

[~andy/linux] / Documentation / DMA-mapping.txt

diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt
index f4ac37f157ea905e06e132c6ee5a1587cb05cbae..10bf4deb96aab3d64060800c256b13d690110214 100644 (file)
--- a/Documentation/DMA-mapping.txt
+++ b/Documentation/DMA-mapping.txt
@@ -194,11 +194,13 @@ document for how to handle this case.
 Finally, if your device can only drive the low 24-bits of
 address during PCI bus mastering you might do something like:
 
-       if (pci_set_dma_mask(pdev, 0x00ffffff)) {
+       if (pci_set_dma_mask(pdev, DMA_24BIT_MASK)) {
                printk(KERN_WARNING
                       "mydev: 24-bit DMA addressing not available.\n");
                goto ignore_this_device;
        }
+[Better use DMA_24BIT_MASK instead of 0x00ffffff.
+See linux/include/dma-mapping.h for reference.]
 
 When pci_set_dma_mask() is successful, and returns zero, the PCI layer
 saves away this mask you have provided.  The PCI layer will use this
@@ -210,7 +212,7 @@ functions (for example a sound card provides playback and record
 functions) and the various different functions have _different_
 DMA addressing limitations, you may wish to probe each mask and
 only provide the functionality which the machine can handle.  It
-is important that the last call to pci_set_dma_mask() be for the 
+is important that the last call to pci_set_dma_mask() be for the
 most specific mask.
 
 Here is pseudo-code showing how this might be done:
@@ -443,15 +445,9 @@ Only streaming mappings specify a direction, consistent mappings
 implicitly have a direction attribute setting of
 PCI_DMA_BIDIRECTIONAL.
 
-The SCSI subsystem provides mechanisms for you to easily obtain
-the direction to use, in the SCSI command:
-
-       scsi_to_pci_dma_dir(SCSI_DIRECTION)
-
-Where SCSI_DIRECTION is obtained from the 'sc_data_direction'
-member of the SCSI command your driver is working on.  The
-mentioned interface above returns a value suitable for passing
-into the streaming DMA mapping interfaces below.
+The SCSI subsystem tells you the direction to use in the
+'sc_data_direction' member of the SCSI command your driver is
+working on.
 
 For Networking drivers, it's a rather simple affair.  For transmit
 packets, map/unmap them with the PCI_DMA_TODEVICE direction