FCP, iSCSI, and Virtual SCSI Client Adapter and Device Interface
The adapter device driver does not contain the ddread and ddwrite entry points, but does contain the ddconfig, ddopen, ddclose, dddump, and ddioctl entry points.
Therefore, the adapter device driver's entry in the kernel devsw table contains only those entries plus an additional ddstrategy entry point. This ddstrategy routine is the path that the device driver uses to pass commands to the device driver. Access to these entry points is possible through the following kernel services:
The adapter is accessed by the device driver through the /dev/fscsi# special files, where # indicates ascending numbers 0, 1, 2, and so on. The adapter is designed so that multiple devices on the same adapter can be accessed at the same time.
The iSCSI adapter is accessed by the device driver through the /dev/iscsin special files, where n indicates ascending numbers 0, 1, 2, and so on. The adapter is designed so that multiple devices on the same adapter can be accessed at the same time.
The Virtual SCSI Client adapter is accessed by the device driver
through the /dev/vscsiX special files, where X indicates
ascending numbers 0, 1, 2,
and so on. The adapter is designed such that multiple devices on the
same adapter can be accessed at the same time.
For additional information on spanned and gathered write commands, see Understanding the Execution of SAM Initiator I/O Requests.