Hello, I enabled the service and restarted the laptop, it was started as expected, but not restarted after suspending, which results in APM levels to not be restored as I feared. However, sometimes it is not reset (or at least that's what I think is happening). I am willing to test a deb package, assuming it will be reasonably safe and I will understand the changes.
I was thinking about how to solve this. After reading through manpages
(systemd-suspend.service(8), systemd.special(8), systemd.unit(8)) I came up
with this possible solution, but it's not working:
Create a file /etc/systemd/system/laptop-mode.service.d/sleep.conf with the
following overrides:
[Unit]
Conflicts=sleep.target
Rationale:
As per systemd.special(8):
sleep.target
A special target unit that is pulled in by suspend.target,
hibernate.target and hybrid-sleep.target and may be used to hook units into
the sleep
state logic.
And from systemd.unit(8)
Conflicts=
A space-separated list of unit names. Configures negative
requirement dependencies. If a unit has a Conflicts= setting on another
unit, starting
the former will stop the latter and vice versa. Note that this
setting is independent of and orthogonal to the After= and Before= ordering
dependencies.
So this means that before systemd goes into suspend or hybrid state which
is signaled by the sleep.target unit, the laptop-mode.service unit should
stop and when the sleep.target unit is stopped after resuming, the
laptop-mode.service should be restarted. However, a unit that was stopped
because of this is not automatically restarted as people in šsystemd on
Freenode explained to me.
As is stated in systemd-sleep(8):
Immediately before entering system suspend and/or hibernation
systemd-suspend.service (and the other mentioned units, respectively) will
run all
executables in /lib/systemd/system-sleep/ and pass two arguments to
them. The first argument will be "pre", the second either "suspend",
"hibernate", or "hybrid-sleep" depending on the chosen action.
Immediately after leaving system suspend and/or hibernation the same
executables are
run, but the first argument is now "post". All executables in this
directory are executed in parallel, and execution of the action is not
continued
until all executables have finished.
Note that scripts or binaries dropped in /lib/systemd/system-sleep/
are intended for local use only and should be considered hacks. If
applications
want to be notified of system suspend/hibernation and resume, there
are much nicer interfaces available.
However, the people in #systemd explained to me that by "nicer interfaces"
DBus is meant, which is not easily applicable for laptop-mode-tools.
A possible system-wide solution was proposed in
https://bugs.debian.org/779370 where a systemd unit would trigger a udev
change that might trigger some of the rules in
/lib/udev/rules.d/99-laptop-mode.rules
Another system-wide solution I would like to propose (but it still doesn't
work for me) is to put a file in /lib/systemd/system-sleep/power-hook which
would support the hooks in /usr/lib/pm-utils/sleep.d/ , including
/usr/lib/pm-utils/sleep.d/01laptop-mode
See the attached file.
However, neither of these work reliably. Sometimes it is set to 128 after
suspend, sometimes it remains at 254 (or is set as expected, I'm not sure).
It almost looks like it's some kind of race issue, but I wasn't able to
find anything relevant with '128' in /etc or /lib.
Kind regards,
Ondrej Grover
pm-hooks
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