Freefall

freefall is a simple daemon providing HDD shock protection for HP laptops supporting the feature officially called "HP Mobile Data Protection System 3D" or "HP 3D DriveGuard".

Kernel
You need to activate the following kernel option either as built-in or as module.

Emerge
The freefall daemon and init script can be found in :

Files
Set the HDD in the configuration file.

OpenRC
Start freefall daemon:

To start freefall at boot time, add it to your boot runlevel:

Testing
After reboot with new kernel, check if hp_accel driver was initialized correctly:

Testing shock protection
Find the HDD's file, it will be somewhere in the  directory:

Go to its directory and run:

Lift the laptop into free space and simulate free fall while holding it firmly. About a 10 cm drop should be enough.

If the disk protection works then the HDD should make "click" sound, see one of your laptop's LEDs flashing and the watch value's background should permanently turn black.