Device Methods for Adapter Cards: Guidelines

The device methods for an adapter card are essentially the same as for any other device. They need to perform roughly the same tasks as those described in "Writing a Device Method" in AIX® Version 7.1 Kernel Extensions and Device Support Programming Concepts. However, there is one additional important consideration. The Bus Configure method, or Bus Configurator, is responsible for discovering the adapter cards present in the system and for assigning bus resources to each of the adapters. These resources include interrupt levels, DMA arbitration levels, bus memory, and bus I/O space.

Adapters are typically defined and configured at boot time. However, if an adapter is not configured due to unresolvable bus resource conflicts, or if an adapter is unconfigured at run time with the rmdev command, an attempt to configure an adapter at run time may occur.

If an attempt is made, the Configure method for the adapter must take these steps to ensure system integrity:

1. Ensure the card is present in the system by reading the POS(0) and POS(1) registers from the slot that is supposed to contain the card and comparing these values with what they are supposed to be for the card.
2. Invoke the busresolve subroutine to ensure that the adapter's bus resource attributes, as represented in the database, do not conflict with any of the configured adapters.

Additional guidelines must be followed when adding support for a new adapter card. They are discussed in:

• Adapter-Specific Considerations for the Predefined Attributes (PdAt) object class
• Writing a Configure Method
• Adapter-Specific Considerations for the Predefined Devices (PdDv) object class