Lenovo ThinkPad P50

Power management
Make sure you have "Hybrid Graphics" enabled in the BIOS, and are using the proprietary NVIDIA driver.

First add a udev rule for putting devices to sleep when not in use:

You'll also want the sound card to sleep when unused, to have direct fan control (just for fun), and to not automatically load the nvidia driver:

Emerge bbswitch and make it load at boot time:

Read onward with the NVIDIA Optimus configuration below to complete the power savings.

Remapping useless FN keys
The keys - to - aren't particularly useful out of the box. A nice application is to (low level) remap the keys to media buttons. This can be done via udev:

and reload the hwdb database:

If this doesn't work, reboot.

Toggle touchpad with FN+F4
To toggle the touchpad with + add an additional line:

TPM (and suspend/resume)
A common problem can be encountered if the TPM chip has been activated in UEFI/BIOS. If the kernel lacks the necessary drivers the system freezes when attempting to resume from a suspend. Simply configuring the kernel with TPM supports resolves the problem: