[fprint] Drivers in user space or kernel space.

[Bastien Nocera]

On Thu, 2012-01-26 at 12:03 -0200, Fausto Carvalho Marques Silva wrote:
> Hi folks,
> i have an old dout about the fingerprint scanner support in the linux 
> world.
> Why does the fingerprint scanners drivers are all written in the user 
> space with libusb and
> not in the kernel space? It would be more easy to configure in ".config" 
> and wide availble if
> it were in the kernel configuration. Many other things seens to be 
> inside the kernel but not
> fingerprint scanners. Do you have any explanation for this (historical 
> or technical?

Simple. Most USB devices with custom protocols are implemented in
user-space because it means that you can avoid having to create a
framework, with much stricter API requirements, in the kernel. If you
were to write kernel drivers, and got the API done, you would probably
need user-space daemons/libraries to talk to the driver.

Finally, user-space is interesting because it means that it works on any
platform where libusb works, including Windows, MacOS X and the *BSDs.