[systemd-devel] RTC on BeagleBone Black or embedded platforms

Mike bellyacres at gmail.com
Thu Feb 27 07:46:35 PST 2014

Hello all

First I'd like to express my gratitude for all the work that is being 
done with systemd.  Until fairly recently I wasn't even aware that the 
project existed.  I often just stay in my comfort zone and don't track 
recent advances...

The boot speed is impressive and the cost of entry from my point of view 
isn't all that expensive.  I've spent a few days reading and 
experimenting with systemd now and I'm sold.

My biggest dilemma at this time right now is with the RTC.  The 
BeagleBone Black does have a RTC and it gets assigned to /dev/rtc0. 
There is however now battery backup for this device.  I've added a 
DS1307 with a battery to allow having a somewhat sane date maintained.  
Therein lies the dilemma, the code is only setup to access /dev/rtc.  
I'm sure that I can figure out with a (gasp) shell script or small c 
program how to set / get the date from the DS1307, it just seems that 
would be a very crude kludge.

My question then is would it be considered to add options to the current 
timedated code that accepted device name and possibly path to the 
appropriate /etc/adjtime file?

More information that may or may not have relevance.  I am using this 
device as an NTP timeserver.  The time sync is from a GPS module with 
PPS.  Ideally this device will have little unpowered time.  Real world 
experience tells me that even with 3 power inputs (Mains supply, solar, 
and Lith-io batt.) it will go down and will come back up way out of sync 
and need manual intervention.

Distro: Debian testing (Jessie)
systemd: version 204
kernel: Linux arm-ticktock 3.8.13-bone40.1 #1 SMP Thu Feb 20 21:12:57 
EST 2014 armv7l GNU/Linux

If this case is too much of an edge case to be considered I can 
understand that.  I would suspect that will all the current embedded 
devices out there that I am not the only one that will hit this issue.

Any help / pointers to RTFM gladly accepted....   I do believe that I've 
done my homework on this though.....

Thanks again for a nice project


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