Validity Sensors, Inc. Swipe Fingerprint Sensor (VendorID:ProductID = 138a:0050) is available on some new laptop models such as the HP Envy 15t. If you plan on installing Ubuntu Linux on such a machine, and wish to experience the luxury of just swiping your finger to log in and do sudo stuff, you would need to get the fingerprint sensor drivers installed properly.
Unfortunately, the default fingerprint driver library libfprint does not (yet) support our sensor. Even fingerprint-gui, the de-facto choice of fingerprint sensor configuration for Ubuntu, fails to detect the device under its default configuration.
Fortunately, someone patched libfprint to include support for several other devices, including our own (138a:0050). You can get the patch from here (courtesy of this AskUbuntu question) to get started.
Before the build, ensure that you have fingerprint-gui installed, following this guide.
The codebase contains an autogen.sh script that would build it for you. However, before building, you will have to have the following packages as build prerequisites (as per Ubuntu 16.04; the versions may vary):
xorg-server-source autoconf automake libtool libusb-1.0-0-dev libnss3-dev libglib2.0-dev libpixman-1-dev
For building, you can either use ./autogen.sh or the following command sequence:
autoreconf --install --force autoconf ./configure make sudo make install
If the last command installs the libraries at /usr/local/lib/ (the location is usually displayed towards the end of the build output), you would have to manually symlink /usr/lib/libfprint.so.0 (currently linked to the existing library in /usr/lib/) to /usr/local/lib/libfprint.so:sudo ln -sf /usr/local/lib/libfprint.so /usr/lib/libfprint.so.0
Now fire up fingerprint-gui and verify that the fingerprint device is detected properly and you can configure and test it. You will also be able to set up fingerprint-based login via Ubuntu's user account settings (might require a system restart).
If you have trouble running fingerprint-gui as a regular user but no problems in superuser mode, you may need to make the corresponding USB device entry accessible for the relevant user/group, or make it universally readable and writable:sudo chmod 666 /dev/bus/usb/BusID/DeviceID
Please post your tips/issues/concerns regarding the 138a:0050 fingerprint sensor here, for the benefit of those who already have it, as well as everyone destined to get hold of one in the near future!