Chapter 13. Using the Programming Interface

SSA Subsystem Overview

Device Drivers

Twotypes of device driver provide support for all SSA subsystems:
vThe SSAadapter device driver, which deals with the SSA adapter.
vThe SSAhead device drivers, which deal with devices that are attached to the SSA
adapter.The SSA disk device driver is an example of an SSA head device driver.
For subsystems that use the Micro Channel SSAMulti-Initiator/RAID EL Adapter, the
PCI SSAMulti-Initiator/RAID EL Adapter, or the Advanced SerialRAID Adapter, the
Target-ModeSSA (TMSSA) device driver is also available. This device driver provides
support for communications from using system to using system. For information about
SSATarget Mode and the TMSSA device driver, see “SSA TargetMode”on page291.

Responsibilities of the SSA Adapter Device Driver

The SSAadapter device driver provides a consistent interface to all SSA head device
drivers, of which the SSAdisk device driver is an example.
The SSAadapter device driver sends commands for SSA devices to the adapter that is
related to those devices. When the SSAadapter device driver detects that the
commands have completed, it informs the originator of the command.

Responsibilities of the SSA Disk Device Driver

The SSAdisk device driver provides support for the SSA disk drives that are connected
to an SSAadapter. That support consists of:
vStandard block I/O to SSAlogical disks, which are represented as hdisks
vCharacter mode I/O to SSAlogical disks, which are represented as rhdisks
vError reporting from SSAphysical disks, which are represented as pdisks
vDiagnostics and service interface to SSAphysical disks that are represented as
pdisks
vRe-issue of commands in the event of an adapter reset
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