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Target drivers deal with the device-specific aspects of the hardware. Most of the time, a hardware device actually consists of a controller card and a physical device (for example, a hard disk and a hard disk controller, or a cartridge tape drive and a tape drive controller). Target drivers deal with the details of operating the physical device (the hard disk, cartridge tape drive, or whatever device is connected to the controller card).
The target driver controls the behavior of a device and decides what device actions are needed to fulfill requests passed to the driver. In this scheme, the HBA driver performs the low-level work of programming the controller to accomplish the actions requested by the target driver.
The following mass storage target drivers are provided.
| Target Driver | Device Type |
|---|---|
| sd01(7) | hard disks |
| st01(7) | tape devices |
| sc01(7) | CD-ROM devices |
| sw01(7) | WORM devices |
| mc01(7) | medium changers |
Additional target drivers might be developed in the future to support other classes of devices which are not currently supported. While the target drivers are architecturally very similar, their differences result from the device-specific aspects which are needed to correctly support each of the device classes.