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Date: Wed, 20 Feb 2008 15:37:28 -0500
From: woodys <woodys@xandros.com>
To: Alessandro Zummo <alessandro.zummo@towertech.it>
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Subject: Re: [rtc-linux] state of GEN_RTC vs rtc subsystem
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Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>, rz@linux-m68k.org,
	rtc-linux@googlegroups.com, LKML Kernel <linux-kernel@vger.kernel.org>
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Alessandro Zummo wrote:
> On Wed, 20 Feb 2008 10:11:23 -0600
> Kumar Gala <galak@kernel.crashing.org> wrote:
>
>   
>> Is the functionality provided by drivers/char/gen_rtc.c completely  
>> handled by the rtc subsystem in drivers/rtc?
>>
>> I ask for two reasons:
>> 1. should we make it mutually exclusive in Kconfig
>> 2. I've enabled both and get (we'll my defconfig did):
>>     
>
>  They shouldn't be enabled at once. I think a patch 
>  for Kconfig has been recently submitted to give a warning
>  in such a case.
>
>  rtc-cmos should be able to handle the vast majority of x86
>  rtcs out there. 
>
>  The only real open issue is related to the ntp synchronization
>  mode and will be solved only when we can get rid of it :)
>
>   
On ARM genrtc has been arbitrary disabled in Kconfig circa 2.6.19 and 
the change to rtc_cmos it is not 100% transparent (ARM Netwinder, Debian).
If I want to use a current (Etch) hwclock binary - I need genrtc with 
/dev/rtc at 10,135, however new rtc_cmos creates /dev/rtc0 at 254,0.
As a result on new kernels hwclock claims that it is not able to access 
hardware.

However upgrading the util-linux package will (sometime in the 
"unstable" future) solve it, so it is not completely broken... Still, at 
the moment - genrtc seems to be a better solution...

Just my $.02...

Woody Suwalski