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To: Grant Erickson <erick205@umn.edu>
Cc: Linux I2C Mailing List <linux-i2c@pelican.tk.uni-linz.ac.at>,
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From: Wolfgang Denk <wd@denx.de>
Subject: Re: Kernel Real Time Clock (RTC) Support for I2C Devices 
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In-Reply-To: Your message of "Wed, 18 Apr 2001 14:13:33 CDT."
             <Pine.SOL.4.20.0104181408540.10793-100000@garnet.tc.umn.edu> 
Date: Wed, 18 Apr 2001 21:40:32 +0200
Message-Id: <20010418194037.C55DB2792B@denx.denx.de>
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Dear Grant,

in message <Pine.SOL.4.20.0104181408540.10793-100000@garnet.tc.umn.edu> you wrote:
> 
> >From the looks of drivers/char/rtc.c it would appear that this kernel
> driver only supports bus-attached RTCs such as the mentioned MC146818. Is
> this correct?

This is correct; however, you can replace this driver by one of  your
own  (see for instance drivers/char/ip860_rtc.c in our version of the
2.4.x Linux sources which implements the RTC driver for a  V3021  RTC
on a IP860 VMEBus system [MPC860 based]).

Right now I'm writing another driver for  the  Philips  PCF8563  RTC,
which is much closer to what you have in mind.

> What is the correct access method / kernel tie-in for supporting such an
> I2C-based RTC device using the "standard" interfaces?

Assuming you have a working I2C driver, just add the necessary "glue"
code to provide the same interface as that of drivers/char/rtc.c .

> My hope is to use 'hwclock' from util-linux w/o modification. Is this
> reasonable?

Yes, this will work (it does for me on the MPC8xx).

Hope this helps,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
The universe does not have laws - it has habits, and  habits  can  be
broken.
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