New DigitalPersona devices have a new firmware. We now use a search
scheme to find the encryption byte, by examining known locations
in the firmware until we find something that we recognise.
A subssm will be executed, and upon completion the parent state machine
will either be advanced to the next state or aborted with error, depending
on the outcome of the subssm.
Also add some debug messages.
Add timeout mechanism as an asynchronous equivalent of sleeping (uru4000
needs this).
Start implementing polling infrastructure which also accounts for pending
timeouts. We don't expose file descriptors yet, but this is a start.
[dsd@gentoo.org: some trivial changes:
fixed some warnings
fixed fp_img memory leak on error
renamed endpoint constants (calling a bulk endpoint 'ctrl' is confusing,
as a control endpoint is something different)
]
After lot 713, Microsoft fingerprint readers changed. The new version
comes with a new USB product ID and a challenge-response authentication
scheme where the device challenges the authenticity of the driver.
An independent third party produced documentation on the computations
needed to convert a challenge into the correct response, and I then used
this documentation to produce a clean-room reimplementation of the
authentication scheme.
bz threshold is now 10 (instead of 15). I think it is ok for the moment.
If we manage to get higher image quality in the future, we'll change that.
max_frame is set to 350. 150 was too low => incomplete fingerprints
the driver was designed to stop the acquisition as soon as it gets a blank
frame (=> incomplete fingerprints). Now it waits to have at least 50 blank
frames before stopping.
This is an active capacitance swipe-type device similar to but smaller
than the AES2501.
Image processing performance is good but matching performance is not so
good. The bozorth3 matcher needs tweaking in order to better cope with
small sets of minutiae.
With a lowered threshold, matching performance is good enough for now.
Fix the functions to conform to the documentation: -1 means non-imaging
device, 0 means variable. Internally, -1 is used to represent variable
height (to be noticably different from the memset-imposed default of zero).
