linux-kernel - Re: [PATCH] RTC: Add mmap method to rtc character driver

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Date:	Tue, 25 Jul 2006 14:01:54 -0400
From:	Jim Gettys <jg@...top.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Neil Horman <nhorman@...driver.com>, linux-kernel@...r.kernel.org,
	a.zummo@...ertech.it, jg@...edesktop.org,
	Keith Packard <keithp@...thp.com>
Subject: Re: [PATCH] RTC: Add mmap method to rtc character driver

On Tue, 2006-07-25 at 19:55 +0200, Arjan van de Ven wrote:
> > @@ -265,6 +269,7 @@ irqreturn_t rtc_interrupt(int irq, void 
> >  
> >  	kill_fasync (&rtc_async_queue, SIGIO, POLL_IN);
> >  
> > +	*count_ptr = (*count_ptr)++;
> 
> Hi,
> 
> it's a cute idea, however 3 questions:
> 1) you probably want to add a few memory barriers around this, right?
> 2) why use the rtc and not the regular timer interrupt?
> 
> (and 
> 3) this will negate the power gain you get for tickless kernels, since
> now they need to start ticking again ;( )

The field only needs to get updated if you've scheduled something to
run...
                            - Jim

> 
> Greetings,
>    Arjan van de Ven
> 
-- 
Jim Gettys
One Laptop Per Child


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