From: Pavel Machek <pavel@ucw.cz>
To: David Brownell <david-b@pacbell.net>
Cc: rtc-linux@googlegroups.com,
kernel list <linux-kernel@vger.kernel.org>,
Alessandro Zummo <alessandro.zummo@towertech.it>
Subject: Re: RTC wakealarm write-only, still has 644 permissions
Date: Thu, 29 Nov 2007 00:26:47 +0100 [thread overview]
Message-ID: <20071128232647.GC4947@elf.ucw.cz> (raw)
In-Reply-To: <200709212238.05130.david-b@pacbell.net>
Hi!
Sorry for long delay. I got rtc wakeup to work... once per boot. On
2.6.24-rc3.
> > > 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
>
> The alarm isn't set; so no value gets displayed.
>
>
> > > root@amd:/sys/class/rtc/rtc0#
> > >
> > >
> > > ...standard PC with reasonably recent kernel...
>
> Yeah, well a "standard PC" is chock full of fairly bizarrely
> glitchey hardware. Clocks and timers have more than their
> fair share, or x86_64 NOHZ support would be merged by now!
Oops. Ok, this is thinkpad x60, if that helps.
> > root@amd:/sys/class/rtc/rtc0# cat wakealarm
> > 2051629528
> > root@amd:/sys/class/rtc/rtc0# date +%s
> > 1190285030
>
> OK, in that situation you've definitely got some buglike behavior.
> My question is: how to fix it?
>
> The problem is that the RTC is reporting an alarm value with some
> fields flagged as "wildcard" -- e.g. day/month/year "out of range"
> so the hardware ignores those fields. This is very common on PC
> based RTCs, and much less common on embedded systems. (Which for
> some reason don't tend to cheap out on full date specs like PCs.)
I see... so situation is not nice :-(.
> I'm not sure which fix would be best; maybe Alessandro has an
> opinion.
Alessandro?
> Better might be
>
> echo $(( $(cat since_epoch) + 20 )) > wakealarm
>
> which has no timezone offset issues.
Good. that actually works.
> > root@amd:/sys/class/rtc/rtc0# cat wakealarm
> > root@amd:/sys/class/rtc/rtc0#
> >
> > Also, is there some documentation for wakealarm?
>
> "git show 3925a5ce44330767f7f0de5c58c6a797009f0f75" has some.
Thanks. Will put it into Doc*/rtc.txt.
> Are you sure it's not working? Other than the two issues I noted
> above -- borkage w.r.t. ACPI (which wasn't necessarily shown in your
> scripts above), and with wildcarding -- it looked to be correct.
It seems to be working now, not sure what changed.
rtc-sysfs.c: why this?
if (alarm > now) {
/* Avoid accidentally clobbering active alarms; we
can't
* entirely prevent that here, without even the
minimal
* locking from the /dev/rtcN api.
*/
retval = rtc_read_alarm(rtc, &alm);
if (retval < 0)
return retval;
if (alm.enabled)
return -EBUSY;
alm.enabled = 1;
People should not be "accidentally" writing to sysfs files...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2007-11-28 23:26 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-20 10:32 RTC wakealarm write-only, still has 644 permissions Pavel Machek
2007-09-20 10:50 ` Pavel Machek
2007-09-22 5:38 ` David Brownell
2007-10-02 9:36 ` Pavel Machek
2007-10-03 2:15 ` David Brownell
2007-11-28 23:26 ` Pavel Machek [this message]
2007-11-29 8:02 ` Tino Keitel
2007-11-29 18:10 ` David Brownell
2007-11-29 18:14 ` Alessandro Zummo
2007-11-30 20:35 ` Pavel Machek
2007-11-30 21:10 ` David Brownell
2007-11-30 21:20 ` Mark Lord
2007-11-30 21:27 ` Pavel Machek
2007-12-02 11:36 ` Pavel Machek
2007-12-02 16:03 ` David Brownell
[not found] ` <20071128230451.GA1547@elf.ucw.cz>
2007-11-28 23:26 ` Pavel Machek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20071128232647.GC4947@elf.ucw.cz \
--to=pavel@ucw.cz \
--cc=alessandro.zummo@towertech.it \
--cc=david-b@pacbell.net \
--cc=linux-kernel@vger.kernel.org \
--cc=rtc-linux@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).