Multiseat Support in HAL

[Artem Kachitchkine]

> It strikes me as being a better solution to just carry the USB traffic
> over the network and channel that data into a dedicated kernel space USB
> host device driver. I believe Sun Ray works that way, I'm sure Artem can
> confirm / deny this. Though, from what I hear doing isosynchronous USB
> transfers over Ethernet is pretty wacky since their are timing
> requirements. I don't really pretend to know :-)

Yeah, Sun Ray moves USB traffic over Ethernet. But they don't reuse any 
of the kernel device driver code - all Sun Ray drivers are in userland 
and have a different set of APIs. There's a very simple loopback kernel 
driver that allows them to pretend they're in the kernel - i.e. accept 
system calls via unix special device files. Where syscall API is not 
required, e.g. for libusb, we avoid this trip to the kernel.

Audio and video on Sun Ray are not USB based. But still tricky. AFAIK 
some X stuff is also a problem, like OpenGL and video acceleration.

-Artem.