[systemd-bugs] [Bug 82243] New: unable to write value on a gpio

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82243

          Priority: medium
            Bug ID: 82243
          Assignee: systemd-bugs at lists.freedesktop.org
           Summary: unable to write value on a gpio
        QA Contact: systemd-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: e92532b8 at opayq.com
          Hardware: ARM
            Status: NEW
           Version: unspecified
         Component: general
           Product: systemd

Created attachment 104144
  --> https://bugs.freedesktop.org/attachment.cgi?id=104144&action=edit
Overview of the commands under discussion

I have an ARM(little endian) arm926t embedded system using a 2.6.39 kernel that
I switch from Busybox to systemd (using buildroot). On Busybox I was able to
write the value of a specific gpio pin via userspace with
# echo 0 > /sys/class/gpio/gpio104/value
nevertheless when I switch to systemd keeping all the other configuration
parameters in buildroot, then the command doesnt work anymore. Also there is no
feedback from the system stating that the operation is not valid, it looks as
if it works but the value doesn't change. if I execute
# more /sys/class/gpio/gpio104/value
1
Not 0 as I requested. The same command works on Busybox but not on the new
systemd. I also if the value maybe was beeing set but not displayed so I
connected an osciloscope to the gpio pin, but as in the software, the value
doesn't change.

The only difference between the two systems is the PID 1 i.e. systemd vs
busybox. Also, with systemd the pin that I want to use is automatically set on
on boot and then later is switch off (by itself) when systemd starts. This
behaviour was also not present when using busybox.

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