[Powertop] Some settings can not be set back from "Good" to "Bad"

[Martin Walch <walch.martin at web.de>]

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Hi,

it is possible to toggle some settings like "Enable Audio codec power 
management" from "Bad" to "Good" and back again. However, when exiting 
powertop while it is set to "Good", and then re-running powertop, the value is 
stuck at "Good", i.e. it is not possible to toggle it to "Bad". When trying to 
do so, the status line only shows ">> (null)" instead of something like "echo 
'' > '/sys/module/snd_hda_intel/parameters/power_save';".

This is probably because sysfs_tunable::bad_value is initialized with "\0" and 
does not change its value if it is already set to "Good" when starting up 
powertop. When now calling sysfs_tunable::toggle(void), strlen(bad_value) is 0 
and the write_sysfs line is not executed.

Is it possible to fix this?

Regards,
Martin Walch
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