Re: [gentoo-user] /dev/rtc => rtc0

[Mark Knecht <markknecht@gmail.com>]

On Sat, Jan 31, 2009 at 2:43 PM, Dale <rdalek1967@gmail.com> wrote:
> Mark Knecht wrote:
>> Hi,
>>    I know nothing of this part of the Linux boot process. If it's
>> *fairly* simple can someone point me at the right stuff to understand
>> how Gentoo creates a link from /dev/rtc to rtc0? When in the boot
>> process does this link become valid?
>>
>>    Is it something that's held in a file and recreated from that file
>> on each boot? Is it created automagically by Gentoo Angels that look
>> after my well being but seldom reveal themselves? Is it created by the
>> kernel itself when something is specifically configured to do so?
>> Something else?
>>
>> Thanks,
>> Mark
>>
>> lightning src # uname -a
>> Linux lightning 2.6.27-gentoo-r8 #6 Fri Jan 30 18:55:56 PST 2009
>> x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux
>> lightning src # ls -al /dev/rtc*
>> lrwxrwxrwx 1 root root      4 2009-01-30 10:58 /dev/rtc -> rtc0
>> crw-r--r-- 1 root root 254, 0 2009-01-30 10:58 /dev/rtc0
>> lightning src #
>>
>>
>>
>
> From my understanding udev creates all the "stuff" in /dev.  You can
> change the rules that it uses to make them tho.  I think there is
> documentation on gentoo.org to help with that.  So far, mine has worked
> well enough.  Lucky I guess.
>
> That help?
>
> Dale

Hi Dale,
   While poking around in a bunch of different kernel config files -
some gentoo-sources - some not - I found there is an option in

Device Drivers -> RTC

that ONLY shows up when you tell the kernel to build the support in.
(I.e. - not off or modular) The option says

<*> Set system time from RTC on startup or resume
(rtc0) RTC used to set the system time

So, it appears it's a kernel oriented thing which allows it to get set
very early in the boot process. My problem on a kernel I built
yesterday was "File has a date in the future" sort of messages. I had
this set as modular so it couldn't load that early. The other problem
was that since it was a module and apparently I didn't load that
module the command hwclock -r failed.

I've reconfigured the kernel and will build it and test after I get
finished with an emerge -e world later today.

Thanks for the response. Hope this info helps someone else in the
future. (and me after the reboot!) ;-)

Cheers,
Mark