For some reason they tend to squat on the very first CSR/
Cambridge Silicon Radio VID/PID instead of paying fees.

This is an extremely common problem; the issue goes as back as 2013
and these devices are only getting more popular, even rebranded by
reputable vendors and sold by retailers everywhere.

So, at this point in time there are hundreds of modern dongles reusing
the ID of what originally was an early Bluetooth 1.1 controller.

Linux is the only place where they don't work due to spotty checks
in our detection code. It only covered a minimum subset.

So what's the big idea? Take advantage of the fact that all CSR
chips report the same internal version as both the LMP sub-version and
HCI revision number. It always matches, couple that with the manufacturer
code, that rarely lies, and we now have a good idea of who is who.

Additionally, by compiling a list of user-reported HCI/lsusb dumps, and
searching around for legit CSR dongles in similar product ranges we can
find what CSR BlueCore firmware supported which Bluetooth versions.

That way we can narrow down ranges of fakes for each of them.

e.g. Real CSR dongles with LMP subversion 0x73 are old enough that
     support BT 1.1 only; so it's a dead giveaway when some
     third-party BT 4.0 dongle reuses it.

So, to sum things up; there are multiple classes of fake controllers
reusing the same 0A12:0001 VID/PID. This has been broken for a while.

Known 'fake' bcdDevices: 0x0100, 0x0134, 0x1915, 0x2520, 0x7558, 0x8891
  IC markings on 0x7558: FR3191AHAL 749H15143 (???)

https://bugzilla.kernel.org/show_bug.cgi?id=60824

Fixes: 81cac64b (Deal with USB devices that are faking CSR vendor)
Reported-by: Michał Wiśniewski <brylozketrzyn@gmail.com>
Tested-by: Mike Johnson <yuyuyak@gmail.com>
Tested-by: Ricardo Rodrigues <ekatonb@gmail.com>
Tested-by: M.Hanny Sabbagh <mhsabbagh@outlook.com>
Tested-by: Oussama BEN BRAHIM <b.brahim.oussama@gmail.com>
Tested-by: Ismael Ferreras Morezuelas <swyterzone@gmail.com>
Signed-off-by: Ismael Ferreras Morezuelas <swyterzone@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>