A.1.2 Supporting SCSI-Specific Functionality

To the system SCSI port driver, a SCSI class driver is a higher-level driver with built-in, SCSI-specific functionality. In general, every SCSI class driver is responsible for the following:

• Connecting itself to the port driver so that requests can be routed to the correct target(s)

• Creating device objects to represent its devices on each SCSI bus in the machine

• Initializing the appropriate controllers (TIDs) and devices (LUs) on the SCSI bus(es)

• Interpreting system I/O requests (IRPs)

• Mapping IRPs to SCSI class/port interface requests (SRBs with SCSI-II CDBs)

• Establishing time-out values for requests

• Limiting the size of data transfers to suit the limits of the underlying HBA

• Handling error conditions that are not already handled by the port driver or the HBA miniport driver, such as check-condition status or bus resets

The following sections describe how class drivers provide this SCSI-specific functionality in the context of each standard routine that class drivers commonly have.