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<base href="https://bugs.freedesktop.org/" />
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<th>Priority</th>
<td>medium
</td>
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<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - unable to write value on a gpio"
href="https://bugs.freedesktop.org/show_bug.cgi?id=82243">82243</a>
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<th>Assignee</th>
<td>systemd-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Summary</th>
<td>unable to write value on a gpio
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>systemd-bugs@lists.freedesktop.org
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux (All)
</td>
</tr>
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<th>Reporter</th>
<td>e92532b8@opayq.com
</td>
</tr>
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<th>Hardware</th>
<td>ARM
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Component</th>
<td>general
</td>
</tr>
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<th>Product</th>
<td>systemd
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=104144" name="attach_104144" title="Overview of the commands under discussion">attachment 104144</a> <a href="attachment.cgi?id=104144&action=edit" title="Overview of the commands under discussion">[details]</a></span>
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.</pre>
</div>
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