ap_driver.h and ESC_AP_DRIVER should be removed
The event definitions in uts/common/sys/sysevent/ap_driver.h and EC_AP_DRIVER in uts/common/sys/sysevent/eventdefs.h can be removed. The entire ap_driver.h should be removed.
These definitions were originally created to support Alternate Pathing 2.3 in the Solaris 8 time frame (I was part of the Alternate Pathing team during that timeframe). Alternate Pathing has never been supported in Solaris 10 or illumos, and these definitions can safely be removed, as there is no viable consumer for them.
This would be a fairly trivial change for someone who wants to try making a change for illumos.