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

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Message-ID: <44C6B117.80300@zytor.com>
Date:	Tue, 25 Jul 2006 17:02:31 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	Segher Boessenkool <segher@...nel.crashing.org>,
	Dave Airlie <airlied@...il.com>, linux-kernel@...r.kernel.org,
	a.zummo@...ertech.it, jg@...edesktop.org
Subject: Re: [PATCH] RTC: Add mmap method to rtc character driver

Neil Horman wrote:
> On Wed, Jul 26, 2006 at 01:29:25AM +0200, Segher Boessenkool wrote:
>>> Yes, but if its in trade for something thats being used currently  
>>> which hurts
>>> more (case in point being the X server), using this solution is a  
>>> net gain.
>> ...in the short term.
>>
> And for any arch that isn't able to leverage a speedup via a vdso implementation
> of a simmilar functionality in the long term

If they can't, then they can't use your driver either.

>>> I'm not arguing with you that adding a low res gettimeofday  
>>> vsyscall is a better
>>> long term solution, but doing that requires potentially several  
>>> implementations
>>> in the C library accross a range of architectures, some of which  
>>> may not be able
>>> to provide a time solution any better than what the gettimeofday  
>>> syscall
>>> provides today.  The /dev/rtc solution is easy, available right  
>>> now, and applies
>>> to all arches.
>> "All"?
>>
> It there any arch for which the rtc driver doesn't function?

Yes, there are plenty of systems which don't have an RTC, or have an RTC 
which can't generate interrupts.

	-hpa

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