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

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Message-Id: <1154213119.28839.76.camel@neko.keithp.com>
Date:	Sat, 29 Jul 2006 15:45:19 -0700
From:	Keith Packard <keithp@...thp.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	keithp@...thp.com, Bill Huey <billh@...ppy.monkey.org>,
	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
Subject: Re: [PATCH] RTC: Add mmap method to rtc character driver

On Sat, 2006-07-29 at 17:43 -0400, Neil Horman wrote:

> Sure, an mmaped jiffy counter would certainly be usefull.  I think the only
> thing left to be determined in this thread is if adding mmap to the rtc driver
> has any merit regardless of any potential users (iow, would current users of
> /dev/rtc find it helpful to have the rtc driver provide an mmap interface.)

A jiffy counter is sufficient for the X server; all I need is some
indication that time has passed with a resolution of 10 to 20 ms. I
check this after each X request is processed as that is the scheduling
granularity. An X request can range in time from .1us to 100 seconds, so
I really want to just check after each request rather than attempt some
heuristic.

-- 
keith.packard@...el.com

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