Hello,
I'm looking at how to adjust the (monotonic) system time from inside the kernel.
Use case is that I have a hw-clock which (not necessarily) regulary sends a timestamp with millisecond precision which I want to use to adjust the system time.
It seems the usual solution to do such, is to use NTP which uses it's own driver (which usually seems to be based on some serial connection):
hw-clock --serial--> kernel --serial-device--> ntpd -> kernel -> system-time
So one solution would be to emulate such a serial device:
hw-clock --> kernel --emulated-serial-device--> ntpd -> kernel -> system-time
Another solution would be to "invent" a ntp-device and write a driver for ntpd to use it:
hw-clock --> kernel --ntp-device--> ntpd -> kernel -> system-time
But I would prefer the following:
hw-clock --> kernel -> system-time
Problem is that the hw-clock in question doesn't offer something like a tick. It just might send a timestamp with millisecond precision whenever it wants.
Because I don't want to reinvent the wheel and because I think there are some people which already have spend some thoughts on similiar things, I'm asking here before I try to implement something which then never might find it's way into the mainline kernel.
Any hints, suggestions, whatever?