iptsd@.service stops itself ~6s after start on cold boot due to StopWhenUnneeded=yes - #219
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StopWhenUnneeded=yes was added in bcb12c6 alongside BindsTo=%I to make sure iptsd stops when its backing hidraw device is removed. BindsTo= already covers that case on its own (see systemd.unit(5): a unit bound to a device is stopped when the device is unplugged). StopWhenUnneeded= instead ties the unit's lifetime to whether any other active unit still "needs" it via a Wants=/Requires= dependency. Since iptsd@.service is only ever started through udev's SYSTEMD_WANTS on the hidraw device unit - a one-time job trigger, not a persistent Wants= - no unit ever durably "needs" it, so systemd stops iptsd a few seconds after every start, even while the device is still present. This breaks touch/pen on cold boot until the device is recreated (e.g. by suspend/resume, which re-triggers the udev rule). Removing StopWhenUnneeded= keeps the intended "stop when device is removed" behavior via BindsTo=, and fixes the premature-stop regression.
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Problem
iptsd@.servicesetsStopWhenUnneeded=yes, but the unit is only everactivated via udev's
SYSTEMD_WANTSon the hidraw device unit - aone-time job trigger, not a persistent
Wants=. As a result, systemddecides nothing "needs" the unit a few seconds after start and stops
it, even though the hidraw device is still present.
On cold boot this means: iptsd starts, connects to the IPTS device,
and is stopped by systemd itself ~6s later. Touch/pen then stop
working until the hidraw device is recreated (e.g. by suspend/resume,
which re-triggers the udev rule).
Evidence
StopWhenUnneeded=yeswas added in bcb12c6 together withBindsTo=%I(later fixed to%i.devicefor escaping in 72afde5),with the stated goal "make sure the service stops when the device is
removed."
systemd.unit(5),BindsTo=already fully covers that case:"...it also does so when a listed unit stops unexpectedly...the
backing device of a device unit might be unplugged."
StopWhenUnneeded=is a different, unrelated mechanism: "a unit willbe automatically cleaned up if no other active unit requires it" -
which is exactly what breaks here, since nothing durably "requires"
a udev-triggered instance.
Reproduction (Surface Pro 4, Fedora 44)
Manual workaround that confirms/fixes it:
systemctl edit iptsd@.servicewith
StopWhenUnneeded=no- service stays active across cold boot,touch/pen work normally. This has also been confirmed working on the
reporter's Surface Pro 4.
Fix
Remove
StopWhenUnneeded=-BindsTo=%i.devicealready provides theoriginally intended "stop on device removal" behavior.
Related KompassOS tracking issue: L0g0ff/KompassOS#85