linux-kernel - Re: [rtc-linux] Re: rtc_cmos: error after first write to wakealarm

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Message-ID: <20070622194417.GA19609@thinkpad.home.local>
Date:	Fri, 22 Jun 2007 21:44:17 +0200
From:	Tino Keitel <tino.keitel@....de>
To:	Alessandro Zummo <alessandro.zummo@...ertech.it>,
	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com
Subject: Re: [rtc-linux] Re: rtc_cmos: error after first write to wakealarm

On Fri, Jun 22, 2007 at 11:45:52 -0700, David Brownell wrote:
> On Friday 22 June 2007, Alessandro Zummo wrote:
> > On Tue, 19 Jun 2007 19:24:29 +0200
> > Tino Keitel <tino.keitel@....de> wrote:
> > 
> > > > > Where is the documentation that describes that I have to disable it
> > > > > first, and how to do this? A migration document for
> > > > > /proc/acpi/alarm users would be nice, too.
> > > > 
> > > >  Well, I guess there is no documentation. Maybe we could add
> > > >  a dev_warn with an explicit message.
> > > 
> > > Isn't it somewhat ridiculous to plan the removal of a feature for
> > > several months, and then replace it with something that behaves
> > > differently without any documentation?
> 
> It's got as much documentation in the kernel tree as that
> old /proc/acpi/alarm thing.  More, in fact, since the GIT
> comment for the putback creating /sys/rtc/.../wakealarm
> files has lots of info about how to use it.

What GIT comment are you referring to?

> 
> But sure, having documentation for the rtc sysfs interface
> would be a Fine Thing.  It should cover the other values
> too, not just that one attribute.
> 
> 
> > > I still wonder how 'cat /sys/class/rtc/rtcX/wakealarm' is expected to
> > > behave. With 2.6.22-rc5, I get this:
> > > 
> > > $ echo 1182351177 > /sys/class/rtc/rtc0/wakealarm 
> > > $ cat /sys/class/rtc/rtc0/wakealarm
> > > 2051644873
> > > 
> > > There seems to be a constant difference of 869984896 seconds. Is this a
> > > bug?
> 
> What RTC driver is that using?

rtc_cmos

> 
> One theory:  it's an RTC that doesn't support all the fields,
> so its driver is returning "-1" in fields like "year" or "month".

With the old /proc/acpi/alarm, the year 2007 became 0007. Maybe this is
the culprit?

Regards,
Tino
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