[arch-general] [PATCH 28/48] Use bash-style conditionals when setting up the hardware clock.

[Victor Lowther]

On Fri, Aug 20, 2010 at 2:12 AM, Kurt J. Bosch
<kjb-temp-2009 at alpenjodel.de> wrote:
> On 2010-08-19 23:12, Victor Lowther wrote:
>>
>> On Aug 19, 2010 10:08 AM, "Kurt J. Bosch"<kjb-temp-2009 at alpenjodel.de>
>> wrote:
>>>
>>> On 2010-08-19 10:19, Jan de Groot wrote:
>>>>
>>>> On Thu, 2010-08-19 at 00:56 -0400, Dave Reisner wrote:
>>>>>
>>>>> Couldn't we avoid all this by just flipping a switch in the kernel?
>>>>>
>>>>> CONFIG_RTC_DRV_CMOS=y
>>>>>
>>>>> If it's compiled into the kernel, udev picks it up and creates
>>>>> the /dev
>>>>> nodes for us.
>>>>
>>>> Which still locks out the people who use a custom kernel with this
>>>> driver compiled as module. IMHO the init scripts should work with both
>>>> module and built-in.
>>>>
>>>
>>> So why not let udev do the job? Patch below. I modified my initcpio to
>>> get rid of the devtmpfs. A ls -l /dev/rtc* added between the new
>>> /sbin/udevadm settle and the initial clock setting showed /dev/rtc0 and
>>> /dev/rtc ->  rtc0. So I think this should work.
>>>
>>> I did *not* move the sysinit_udevlaunched hook together with udev start
>>> to avoid insane creation times of dev nodes because this hook is used
>>> for some early udev triggering in fbsplash-extras (AUR).
>>>
>>> Patch against bashification-redux:
>>>
>>>  From 22d410a2566964d58752d443a1312a6eb552660a Mon Sep 17 00:00:00 2001
>>> From: Kurt J. Bosch<kjb-temp-2009 at alpenjodel.de>
>>> Date: Thu, 19 Aug 2010 16:46:23 +0200
>>> Subject: [PATCH 17/17] Correct rtc dev nodes creation using udev
>>>
>>> ---
>>> rc.sysinit | 22 +++++++---------------
>>> 1 files changed, 7 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/rc.sysinit b/rc.sysinit
>>> index 4421def..2415967 100755
>>> --- a/rc.sysinit
>>> +++ b/rc.sysinit
>>> @@ -46,6 +46,12 @@ else
>>> /bin/dmesg -n 3
>>> fi
>>>
>>> +echo>  /proc/sys/kernel/hotplug
>>> +
>>> +stat_busy "Starting UDev Daemon"
>>> +/sbin/udevd --daemon
>>> +stat_done
>>> +
>>> HWCLOCK_PARAMS="--hctosys"
>>> case $HARDWARECLOCK in
>>> UTC) HWCLOCK_PARAMS+=" --utc";;
>>> @@ -56,15 +62,7 @@ esac
>>> if [[ $HWCLOCK_PARAMS ]]; then
>>> # enable rtc access
>>> /sbin/modprobe -q -a rtc-cmos rtc genrtc
>>> - # If devtmpfs is used, the required RTC device already exists now
>>> - # Otherwise, create whatever device is available
>>> - if ! [[ -c /dev/rtc || -c /dev/rtc0 ]]; then
>>> - for dev in /sys/class/rtc/rtc0/dev /sys/class/misc/rtc/dev; do
>>> - [[ -e $dev ]] || continue
>>> - IFS=: read -r major minor<  "$dev"
>>> - /bin/mknod /dev/rtc c $major $minor
>>> - done
>>> - fi
>>> + /sbin/udevadm settle
>>>
>>> # Do a clock set here for a few reasons:
>>> # 1. Make creation time on udev nodes sane (FS#8665)
>>> @@ -79,12 +77,6 @@ if [[ $HWCLOCK_PARAMS ]]; then
>>> fi
>>> fi
>>>
>>> -echo>  /proc/sys/kernel/hotplug
>>> -
>>> -stat_busy "Starting UDev Daemon"
>>> -/sbin/udevd --daemon
>>> -stat_done
>>> -
>>> run_hook sysinit_udevlaunched
>>>
>>> # Trigger udev uevents
>>> --
>>> 1.7.2.1
>>>
>>>
>
>> I like this one the best.
>>
>> Sent from my Nexus One. Sorry for top posting.
>>
> Corrected
>
> Hmm, the patch might break things with custom non modular kernels without
> devtmpfs though. No modules loading no uevents and no dev nodes. On the
> other hand reading the hwclock man page, I'm a bit uncertain whether that
> piece will ever use /dev/rtc0 without a symlink from /dev/rtc. Instead it
> might actually fall back to direct I/O with the current code and with the
> patched one too.
>
> Moreover I found a couple of interesting things:
> * The system clock is already set (by the kernel - in spite of
> CONFIG_RTC_HCTOSYS not set) even without doing anything. Weird, but with UTC
> hardware clock I even get correct mtimes in early user space.
> * man hwclock:
>> --systz
>> Reset the System Time based on the current timezone.
>> ...
>> This is an alternate option to --hctosys that does not read the
>> hardware clock, and may be used in system startup scripts for recent
>> 2.6 kernels where you know the System Time contains the Hardware
>> Clock time.
> I switched my hardware clock to localtime, reverted my patch and modified
> rc.sysinit to use -systz instead of --hctosys for the first hwclock call and
> also disabled the entire rtc modprobe and mknod code. A date command
> inserted for testing spit out the correct time.
> From the util-linux-ng list:
>> Indeed, we may be running hwclock --systz before /dev is mounted.
> Getting rid of the pre fsck hwclock --hctosys would also on the average save
> another half second of boot up time beside removing some ugly code.
>
> AFAIKS we can go one of three ways:
> * Use udev expecting CONFIG_RTC_DRV_CMOS=m or fall back to direct I/O
> * Use --systz, drop the ugly code and expect some help from the kernel
> * Use an even more ugly code creating the missing symlink:
>
> Corrected non udev patch against bashification-redux:
>
> From 4e5d6a763af8f45c63ad53aa99b82246f90c0b43 Mon Sep 17 00:00:00 2001
> From: Kurt J. Bosch <kjb-temp-2009 at alpenjodel.de>
> Date: Fri, 20 Aug 2010 09:04:46 +0200
> Subject: [PATCH 17/17] Really correct rtc dev nodes creation
>
> ---
>  rc.sysinit |   15 +++++++++------
>  1 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/rc.sysinit b/rc.sysinit
> index 4421def..1ff37cc 100755
> --- a/rc.sysinit
> +++ b/rc.sysinit
> @@ -58,12 +58,15 @@ if [[ $HWCLOCK_PARAMS ]]; then
>        /sbin/modprobe -q -a rtc-cmos rtc genrtc
>        # If devtmpfs is used, the required RTC device already exists now
>        # Otherwise, create whatever device is available
> -       if ! [[ -c /dev/rtc || -c /dev/rtc0 ]]; then
> -            for dev in /sys/class/rtc/rtc0/dev /sys/class/misc/rtc/dev; do
> -                [[ -e $dev ]] || continue
> -               IFS=: read -r major minor < "$dev"
> -               /bin/mknod /dev/rtc c $major $minor
> -           done
> +       if ! [[ -c /dev/rtc ]]; then
> +               for dev in /sys/class/misc/rtc /sys/class/rtc/rtc0; do
> +                       [[ -e $dev/dev ]] || continue
> +                       IFS=: read -r major minor < "$dev/dev"
> +                       node=${dev##*/}
> +                       /bin/mknod /dev/$node c $major $minor
> +                       [[ $node = rtc ]] || /bin/ln -s $node /dev/rtc
> +                       break
> +               done
>        fi
>
>        # Do a clock set here for a few reasons:
> --
> 1.7.2.1

Thanks, I will apply this to bashification-redux.

> --
> Kurt
>
>
>