lkml.org 
[lkml]   [2007]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [rtc-linux] Re: rtc_cmos: error after first write to wakealarm
    On Tue, Jun 19, 2007 at 14:24:04 +0200, Alessandro Zummo wrote:
    > On Fri, 15 Jun 2007 09:03:19 +0200
    > Tino Keitel <tino.keitel@gmx.de> wrote:
    >
    > > > > I have the following strange behaviour with rtc_cmos:
    > > > >
    > > > > $ echo 1181934240 > /sys/class/rtc/rtc0/wakealarm
    > > > > bash: echo: write error: Device or resource busy
    > > > > $ rmmod rtc_cmos
    > > > > $ modprobe rtc_cmos
    > > > > $ echo 1181934240 > /sys/class/rtc/rtc0/wakealarm
    > > > > $ echo 1181934240 > /sys/class/rtc/rtc0/wakealarm
    > > > > bash: echo: write error: Device or resource busy
    > > > > $
    > > >
    > > > If the alarm has already been enabled, you cannot set the next
    > > > alarm. You should disable first.
    > >
    > > Ah, ok.
    > >
    > > 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?

    I don't know if there is any centralized form sysfs documentation. I
    guess not. So at least a short text like the one below somewhere in
    Documentation/ would be useful.

    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?


    -----------------------------------------------------------------------

    How to use /sys/class/rtc/rtcX/wakealarm
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    This file takes the seconds since epoch to enable a wake event at the
    specified time.

    If a '0' is written, the alarm is disabled.

    If the alarm was already enabled, a new alarm can only be set after the
    old alarm is disabled.


    Migration from /proc/acpi/alarm
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    Users of /proc/acpi/alarm have to change their code to supply the
    seconds since epoch instead of a date string.

    For shell scripts, this can be done using the date command, e.g. like
    this:

    date -d tomorrow "+%s"

    This returns the seconds since epoch of the current time on the
    following day.

    Please note that you have to disable the old alarm first, if you want
    to set a new alarm. Otherwise, you get an error. Example:

    echo 12345 > /sys/class/rtc/rtc0/wakealarm
    echo 0 > /sys/class/rtc/rtc0/wakealarm
    echo 23456 > /sys/class/rtc/rtc0/wakealarm

    -----------------------------------------------------------------------

    Regards,
    Tino
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-06-19 19:27    [W:0.028 / U:19.556 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site