When idconfupdate is invoked without options, it reads the Resource Manager database from /dev/resmgr, and performs two functions:
Only sdevice files for hardware drivers are affected; a hardware driver is identified by having an ``h'' in the flags field of its Master file.
All drivers that are not in the Resource Manager database are turned off. That is, the ``config'' field of each line in their sdevice files is changed from ``Y'' to ``N''.