linux-kernel - Re: RTC wakealarm write-only, still has 644 permissions

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Message-ID: <20070920105002.GA4611@elf.ucw.cz>
Date:	Thu, 20 Sep 2007 12:50:02 +0200
From:	Pavel Machek <pavel@....cz>
To:	a.zummo@...ertech.it, rtc-linux@...glegroups.com,
	kernel list <linux-kernel@...r.kernel.org>,
	dbrownell@...rs.sourceforge.net
Subject: Re: RTC wakealarm write-only, still has 644 permissions

Hi!

> ...should they be changed to 200? Or perhaps file should be readable?
> 
> root@amd:/sys/class/rtc/rtc0# cat wakealarm 
> root@amd:/sys/class/rtc/rtc0# echo 132719 > wakealarm 
> root@amd:/sys/class/rtc/rtc0# ls -al wakealarm 
> -rw-r--r-- 1 root root 0 Sep 20 12:30 wakealarm
> root@amd:/sys/class/rtc/rtc0# cat wakealarm 
> root@amd:/sys/class/rtc/rtc0# cat wakealarm 
> root@amd:/sys/class/rtc/rtc0# 
> 
> 
> ...standard PC with reasonably recent kernel...

Hmm, something is definitely wrong in here. I sometimes _do_ get
something back.

root@amd:~# s2ram
Switching from vt9 to vt1


switching back to vt9
root@amd:~# 
root@amd:~# 
root@amd:~# cd /sys/class/rtc/rtc0
root@amd:/sys/class/rtc/rtc0# ls
date  dev  device@  name  power/  since_epoch  subsystem@  time
uevent  wakealarm
root@amd:/sys/class/rtc/rtc0# cat wakealarm 
2051629528
root@amd:/sys/class/rtc/rtc0# cat power/wakeup 

root@amd:/sys/class/rtc/rtc0# cat wakealarm 
2051629528
root@amd:/sys/class/rtc/rtc0# date +%s
1190285030
root@amd:/sys/class/rtc/rtc0# echo 1190285050 > wakealarm 
root@amd:/sys/class/rtc/rtc0# s2ram
Switching from vt9 to vt1


switching back to vt9
root@amd:/sys/class/rtc/rtc0# 
root@amd:/sys/class/rtc/rtc0# 
root@amd:/sys/class/rtc/rtc0# cat wakealarm 
root@amd:/sys/class/rtc/rtc0# cat wakealarm 
root@amd:/sys/class/rtc/rtc0# date +%s
1190285229
root@amd:/sys/class/rtc/rtc0# cat wakealarm 
root@amd:/sys/class/rtc/rtc0# 

Also, is there some documentation for wakealarm?

sh-3.1$ cd Documentation/
sh-3.1$ grep -ri wakealarm .

...is it time in seconds? In UTC? In whatever timezone rtc clocks are
using? It does not seem to work for me :-(.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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