diff options
Diffstat (limited to 'Documentation/DMA-mapping.txt')
| -rw-r--r-- | Documentation/DMA-mapping.txt | 12 |
1 files changed, 3 insertions, 9 deletions
diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt index f4ac37f157ea..684557474c15 100644 --- a/Documentation/DMA-mapping.txt +++ b/Documentation/DMA-mapping.txt | |||
| @@ -443,15 +443,9 @@ Only streaming mappings specify a direction, consistent mappings | |||
| 443 | implicitly have a direction attribute setting of | 443 | implicitly have a direction attribute setting of |
| 444 | PCI_DMA_BIDIRECTIONAL. | 444 | PCI_DMA_BIDIRECTIONAL. |
| 445 | 445 | ||
| 446 | The SCSI subsystem provides mechanisms for you to easily obtain | 446 | The SCSI subsystem tells you the direction to use in the |
| 447 | the direction to use, in the SCSI command: | 447 | 'sc_data_direction' member of the SCSI command your driver is |
| 448 | 448 | working on. | |
| 449 | scsi_to_pci_dma_dir(SCSI_DIRECTION) | ||
| 450 | |||
| 451 | Where SCSI_DIRECTION is obtained from the 'sc_data_direction' | ||
| 452 | member of the SCSI command your driver is working on. The | ||
| 453 | mentioned interface above returns a value suitable for passing | ||
| 454 | into the streaming DMA mapping interfaces below. | ||
| 455 | 449 | ||
| 456 | For Networking drivers, it's a rather simple affair. For transmit | 450 | For Networking drivers, it's a rather simple affair. For transmit |
| 457 | packets, map/unmap them with the PCI_DMA_TODEVICE direction | 451 | packets, map/unmap them with the PCI_DMA_TODEVICE direction |