[okl4-developer] OKL4 : How can I get time?

[Nelson Tam]

Hi Martin and all,

Thanks for the response, you pretty much nailed it right on.

I just wanted to add that for the 2.1 release, we have implemented a  
Real Time Clock (RTC) driver for all supported architectures, so that  
may help you with getting a clock that corresponds to real world time,  
albeit at a lower resolution.

Nelson.

On 25/04/2008, at 6:33 PM, Martin P. Lawitzky wrote:
>
> inside the kernel the scheduler has a current time. Outside the kernel
> without using the Iguana vtimer, you will have to map the timer
> interrupt register and timer match registers to the space where you  
> want
> to implement you own timer. The roottask can do this.
> This is what the Iguana vtimer does.
>
> Depending on the architecture you might need to be careful here, not  
> to
> overwrite the timer settings used by the scheduler. If you  
> accidentally
> remove the timer interrupt of the scheduler, your tasks will never be
> preempted anymore. So this is a potential security issue and these
> registers shouldn't be mapped to arbitrary tasks.
>
> Using cycle counters works only in privileged mode on some
> architectures, so you would need to implement a syscall for this which
> likely screws up your timing anyway.
>
> So, do you need the time inside the kernel or in userland?

--
(nt)

Nelson Tam

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