Re: [patch 1/3] hpet: factor timer allocate from open

Re: [patch 1/3] hpet: factor timer allocate from open

[Thomas Gleixner]

On Tue, 20 Jul 2010, akpm@linux-foundation.org wrote:

> From: Magnus Lynch <maglyx@gmail.com>
> 
> The current implementation of the /dev/hpet driver couples opening the
> device with allocating one of the (scarce) timers (aka comparators).  This
> is a limitation in that the main counter may be valuable to applications
> seeking a high-resolution timer who have no use for the interrupt
> generating functionality of the comparators.

And how exactly does this patch provide such functionality ? There is
no interface which allows you to access the counter itself. All what
this patch does is removing the allocation from open() and sprinkle
the allocation all over the place for _ZERO_ benefit.

I really have a hard time to understand why anything would open
/dev/hpet just to do nothing with it.

Thanks,

	tglx

Re: [patch 1/3] hpet: factor timer allocate from open

[Clemens Ladisch]

Thomas Gleixner wrote:
> On Tue, 20 Jul 2010, akpm@linux-foundation.org wrote:
> > From: Magnus Lynch <maglyx@gmail.com>
> > 
> > The current implementation of the /dev/hpet driver couples opening the
> > device with allocating one of the (scarce) timers (aka comparators).  This
> > is a limitation in that the main counter may be valuable to applications
> > seeking a high-resolution timer who have no use for the interrupt
> > generating functionality of the comparators.
> 
> And how exactly does this patch provide such functionality ? There is
> no interface which allows you to access the counter itself.

Through mmap(); this is the only interface of /dev/hpet that is actually
used in practice.

> Cc: Clemens Ladisch <clemens@ladisch.de>

Acked-by: Clemens Ladisch <clemens@ladisch.de>


Regards,
Clemens

Re: [patch 1/3] hpet: factor timer allocate from open

[Mag]

On Fri, Jul 23, 2010 at 6:07 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> And how exactly does this patch provide such functionality ? There is
> no interface which allows you to access the counter itself.

Yes there is, mmap allows you access the registers.