Devices should expose a flag if they support stay awake indefinitely (for verification)
Ideally we want to be able to show a login prompt and for the whole time the greeter is shown a device will be able to unlock the system without any further user interaction (at least while the screen device is turned on, but that's an upper-level design decision, so ideally for the whole time).
While this is something we can give for granted for all the modern devices, there have been cases of old ones which were not able to stay in verification state for long times, and needed to be reset. Thus currently PAM module is using a timeout, stopping a device verification after that.
Given this, we need:
-
libfprint device API to expose if a driver is able to stay awake (I'd default to TRUE if not set)
- Maybe should set a
maximum-activetime property, defining its timeout.
- Maybe should set a
- fprintd should handle this internally (so the PAM module option will only set the higher bound) stopping a device action if it's running for more time the device supports. Emitting the relevant signal to clients.
Related to: https://gitlab.gnome.org/Teams/Design/os-mockups/-/issues/56, fprintd!89, fprintd#9