Yoga 920 fn-lock and conservation mode acpi platform driver. Actually it should be work on next models: Yoga 700, Yoga 710, Yoga 720, Yoga 900, Yoga 910, Yoga 920, but this information needs confirmation. Please NOTE: this code provided as is. You have to use it at your own risk.

While this module was tested on 4.15 kernels(i guess it will also work with ealer versions of linux kernel), 4.18 kernel module ideapad_laptop supports fn_lock functionality out-of-box. So if you have 4.18 kernel you do not need ideapad-hacks.

1. Be sure actual kernel headers installed
2. Clone repo, change directory and type make

1. sudo insmod ideapad-hacks.ko
2. sudo find /sys -name "fn_lock"
3. In my case find says /sys/devices/pci0000:00/0000:00:1f.0/PNP0C09:00/VPC2004:00/fn_lock
4. Check current fn_lock value: sudo cat /sys/devices/pci0000:00/0000:00:1f.0/PNP0C09:00/VPC2004:00/fn_lock
5. Write new setting sudo echo 0 > /sys/devices/pci0000:00/0000:00:1f.0/PNP0C09:00/VPC2004:00/fn_lock

ideapad-hacks is not compatible with ideapad_laptop kernel module from linux kernel mainline. To use ideapad you MUST unload or blacklist ideapad_laptop. Ideapad-hacks is temporary solution and it will be deprecated as soon as fn_lock related patches will be reviewed and applyed by linux kernel mantainers.