If we were totally rigurous about representing each device as a device node,
your solution would be fine. But we don't.
The clocksource model (/sys/devices/system/clocksource) is a better way to
go. One sysfs file is used to enumerate the possible sources and another is
used to read or set the current source. No new system calls; no new ioctls.
-ch
ch (at) murgatroid (dot) com
ch (at) hpl (dot) hp (dot) com
-