The fingerprint reader of a Thinkpad T4** can be used on Linux together with the fprintd library for the usual gdm login in. But there is no way to use the fingerprint reader at power on even a power on password was defined 🙁
The problem is that the fingerprint has to be written into the bios to get a pre-desktop / pre-boot authentication.
There is no way to write it on Linux.
A native Win* installation is needed… I haven’t it and won’t it!
Using VirtualBox I was able to write the fingerprint into the real bios of the T400. Windows XP Professional as guest was used, running “setup32_xvp.exe”, downloaded here from Lenovo. At first I got a strange “C:\WINDOWS path too long” error message as a part of the *.msi installation… Really strange.
However I have fixed this at the end: And my fingerprint was saved to into the Thinkpad bios with success!
The Lenovo software for Windows isn’t needed any more afterwards.
As a final step the gdm login can be disabled to make things 100% comfortable – by booting directly into the preferred user environment (System Settings -> User Accounts). Nice 😉