Capability Modules and APIs

This appendix describes some general-purpose capability modules and their APIs.

Some general notes about capability modules:

• To obtain the pci_cap_t structure operated on by the specific capability module API, call pci_device_read_cap().
• The module-specific APIs provide a means of querying and configuring capability-specific attributes by operating on the pci_cap_t structure. Changes don't actually take effect until you successfully call pci_device_cfg_cap_enable().
• The module-specific APIs aren't available to driver software until you successfully call pci_device_read_cap(). Software doesn't link against a capability module.
• In order to change capability attributes, you must disable the capability before re-enabling it with an updated pci_cap_t.
• When you no longer need a pci_cap_t obtained from a successful pci_device_read_cap() call, you can release it by calling free().