Module Name:	src
Committed By:	thorpej
Date:		Tue Nov 17 08:38:08 UTC 1998

Modified Files:
	src/sys/kern: subr_autoconf.c
	src/sys/sys: device.h
Log Message:
Implement config_detach(), mostly from Chris Demetriou, modified slightly
by Ken Hornstein and myself.

Add flags to struct device, and define one as "active".  Devices are
initially active from config_attach().  Their active state may be changed
via config_activate() and config_deactivate().

These new functions assume that the device being manipulated will recursively
perform the action on its children.

Together, config_deactivate() and config_detach() may be used to implement
interrupt-driven device detachment.  config_deactivate() will take care of
things that need to be performed at interrupt time, and config_detach()
(which must run in a valid thread context) finishes the job, which may
block.