Fragmented Commands

Single I/O requests larger than the maximum transfer size must be divided into smaller requests by the device driver.

For calls to a device driver’s character I/O (read/write) entry points, the uphysio kernel service can be used to break up these requests. For a fragmented command such as this, the scsi_buf.bp field should be null so that the adapter device driver uses only the information in the scsi_buf structure to prepare for the DMA operation.