SSA Subsystem Overview

Device Drivers

Two types of device driver provide support for all SSA subsystems:

• The SSA adapter device driver, which deals with the SSA adapter.

• The SSA head 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 subsytems that use Micro Channel Enhanced SSA Multi-Initiator/RAID EL Adapters or PCI SSA Multi-Initiator/RAID EL Adapters, the Target-Mode SSA (TMSSA) device driver is also available. This device driver provides support for communications from using system to using system. For information about SSA Target Mode and the TMSSA device driver, see SSA Target Mode.

Responsibilities of the SSA Adapter Device Driver

The SSA adapter device driver provides a consistent interface to all SSA head device drivers, of which the SSA disk device driver is an example.

The SSA adapter device driver sends commands for SSA devices to the adapter that is related to those devices. When the SSA adapter device driver detects that the commands have completed, it informs the originator of the command.

Responsibilities of the SSA Disk Device Driver

The SSA disk device driver provides support for the SSA disk drives that are connected to an SSA adapter. That support consists of:

• Standard block I/O to SSA logical disks, which are represented as hdisks

• Character mode I/O to SSA logical disks, which are represented as rhdisks

• Error reporting from SSA physical disks, which are represented as pdisks

• Diagnostics and service interface to SSA physical disks that are represented as pdisks

• Re-issue of commands in the event of an adapter reset

Interface between the SSA Adapter Device Driver and Head Device Driver

To communicate with the SSA adapter device driver, the SSA head device driver:

1. Uses the fp_open kernel service to open the required instance of the SSA adapter device driver.

2. Calls the fp_ioctl kernel service to issue the SSA_GET_ENTRY_POINT operation to the opened adapter.

3. Calls the function SSA_Ipn_Directive whose address was returned by the ioctl operation. These calls to SSA_Ipn_Directive are used for all communication with the SSA device.

4. Uses the fp_close kernel service to close the adapter.

Note:When fp_close is called, SSA_Ipn_Directive cannot be called.

Trace Formatting

The SSA adapter device driver and the SSA disk device driver can both make entries in the kernel trace buffer. The hook ID for the SSA adapter device driver is 45A. The hook ID for the SSA disk device driver is 45B. For information on how to use the kernel trace feature, refer to the trace command for the kernel debug program. With the PCI SSA Multi-Initiator/RAID EL Adapter and Micro Channel Enhanced SSA Multi-Initiator/RAID EL Adapter, the Target-Mode SSA device driver can make entries in the kernel trace buffer; its hook ID is xxx.

Related Information

The SSA Adapter Device Driver, ssadisk SSA Disk Device Driver.

Trace Command for the Kernel Debug Program.