Layered Drivers

Layered Drivers

IRIX allows for "layered" device drivers, in which one driver operates the actual hardware and the driver at the higher layer presents the programming interface. This approach is implemented for SCSI devices: actual management of the SCSI bus is delegated to a set of Host Adapter drivers. Drivers for particular kinds of SCSI devices call the Host Adapter driver through an indirect table to execute SCSI commands. SCSI drivers and Host Adapter drivers are discussed in detail in Chapter 15, "SCSI Device Drivers."