TL-WN722N support on FreeBSD.

[atar]

Here's additional place where FreeBSD has lack of support: USB based printers.

Here's a citation from the FreeBSD handbook (page no. 251):

> USB interfaces, named for the Universal Serial Bus, can run at even faster speeds than parallel or RS-232 serial interfaces. Cables are simple and cheap. USB is superior to RS-232 Serial and to Parallel for printing, but it is not as well supported under UNIX systems. A way to avoid this problem is to purchase a printer that has both a USB interface and a Parallel interface, as many printers do.
> 
>> Hi,
>> 
>> The main issue is this: I really don't like the USB driver stuff in the kernel.
>> 
>> When I last checked, there was no clean example of a wifi or ethernet
>> driver which handles all of the odd corner cases of things correctly.
>> So you'd end up with things like taskqueues still running whilst the
>> NIC had been pulled out, all sleeping on a wakeup that'll never come,
>> or the ioctl path not really being locked the right way with the rest
>> of the USB driver.
>> 
>> I started tinkering with a driver for the AR9170, but I still couldn't
>> get the command handling side of things right. It's tricky because USB
>> is effectively a network protocol, but all the drivers are written
>> assuming register accesses are synchronous. So you end up having to
>> craft some kind of command structure that handles sleeping for
>> commands that it expects a response on from another USB endpoint (eg
>> register reads), but not sleeping for commands that are asynchronous.
>> I gave up because it became "non-fun."
>> 
>> So yeah. Almost all of the work is done in the atheros driver side of
>> things. Heck, the AR9271 bits for the HAL are likely just an evenings
>> worth of work for me. I just don't want to deal with the USB side of
>> it.
>> 
>> I'm not being paid to do any of the wireless stuff in FreeBSD, so it
>> has to clear the "is it fun" threshold.
>> 
>> 
>> -a