apic detection

[John Baldwin]

On Thursday 15 June 2006 14:23, Andriy Gapon wrote:
> on 15/06/2006 20:10 John Baldwin said the following:
> > On Wednesday 14 June 2006 12:33, Andriy Gapon wrote:
> >> What is proper way to check from a driver/module if APIC is being used ?
> >> Or even narrower, if local APIC timer is being used ?
> > 
> > There isn't currently.  Why do you need to know?
> > 
> 
> There is a driver that I am working on that could change frequency of
> local APIC timer by changing FSB frequency and I want to make that
> driver smarter and refuse to attach if local APIC timer is used. I know
> that in 6.X and CURRENT local APIC timer is always used and in 5.X it is
> never used, but I want my driver to handle environment more generally.

It it always used if APIC is used.

> I am thinking, can I just somehow check if IRQ0 is in use ? Would it be
> something close to proper solution ?

On x86 there is a variable called 'using_lapic_timer' that is available in
sys/i386/isa/clock.c (and the amd64 equivalent), but I think it is static to
that file, so you probably can't get to it.  Other than that there really
isn't a current way to know as the vast majority of the system does not
(and should not) know or care.

-- 
John Baldwin