[fprint] AES2501 and async interface to libfprint

[Daniel Drake]

Christian Schaubschlaeger wrote:
> None of these function calls return an error.
> The problem is, that the callback function 'enroll_stage_cb'
> never gets called; it seems, that fp_async_enroll_start does not
> initiate scanning...

libfprint isn't threaded, so it has no immediate way of carrying out the 
work you just asked it to do. You have to run an event handler for it, 
which in most cases you can integrate into your main event loop  (it is 
based on file descriptors). I'm sorry that there is really no 
documentation for this yet, but you could look at fprint_demo which 
makes fprint event handling part of GTK+'s mainloop, fprintd as well. 
Also the libusb-1.0 documentation might be useful because libusb-1.0 is 
based on identical principles.

Daniel