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

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Message-Id: <1154216151.2467.5.camel@entropy>
Date:	Sat, 29 Jul 2006 16:35:51 -0700
From:	Nicholas Miell <nmiell@...cast.net>
To:	Bill Huey <billh@...ppy.monkey.org>
Cc:	Edgar Toernig <froese@....de>, Neil Horman <nhorman@...driver.com>,
	Jim Gettys <jg@...top.org>, "H. Peter Anvin" <hpa@...or.com>,
	Dave Airlie <airlied@...il.com>,
	Segher Boessenkool <segher@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, a.zummo@...ertech.it,
	jg@...edesktop.org, Keith Packard <keithp@...thp.com>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: itimer again (Re: [PATCH] RTC: Add mmap method to rtc
	character driver)

On Sat, 2006-07-29 at 15:51 -0700, Bill Huey wrote:
> On Sat, Jul 29, 2006 at 11:49:48PM +0200, Edgar Toernig wrote:
> > Bill Huey (hui) wrote:
> > > Well, this points out a serious problem with doing an mmap extension to
> > > /dev/rtc. It would be better to have a page mapped by another device like
> > > /dev/jiffy_counter, or something like that rather than to overload the
> > > /dev/rtc with that functionality.
> > 
> > You mean something like this, /dev/itimer?
> > 
> >     http://marc.theaimsgroup.com/?m=115412412427996
> 
> [CCing Steve and Ingo on this thread]
> 
> It's a different topic than what Keith needs, but this is useful for another
> set of purposes. It's something that's really useful in the RT patch since
> there isn't a decent API to get at high resolution timers in userspace. What
> you've written is something that I articulated to Steve Rostedt over a dinner
> at OLS and is badly needed in the -rt patches IMO. I suggest targeting that
> for some kind of inclusion to Ingo Molnar's patchset.
> 

Do you mind summarizing what's wrong with the existing interfaces for
those of us who didn't have the opportunity to join you for dinner at
OLS?

-- 
Nicholas Miell <nmiell@...cast.net>

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