[Spice-devel] Questions on usbredir + XSpice redux, libusb anyone?

[Alex Wauck]

I've found one potential sticking point: RHEL 6 (not sure about 7) apparently
builds CUPS without the libusb backend.  They apparently prefer to use the usblp
kernel module and then access USB printers via /dev/usb/lpXXX using the usb-unix
backend.  More recent distros (at least Arch and Fedora 21) appear to use libusb.
A bit of searching (and one of the patches Red Hat applied to their cups package)
suggests that the transition from the old way to the libusb way was rather
disruptive.

Thankfully, It does not appear that SANE ever did anything similar.

On Mon, 13 Apr 2015 14:40:44 -0500
Jeremy White <jwhite at codeweavers.com> wrote:

> Hi folks,
> 
> I've done some work on a usbredir kernel module to bring support for USB
> to XSpice.   In doing so, and talking with some colleagues, their
> reaction was:  why don't you modify libusb instead?
> 
> That is, the current change is to modify XSpice to pipe the USBREDIR
> protocol bytes out to a unix domain socket, and then into the kernel
> module from there.  However, if you think about it, most Linux
> applications (e.g. most apps running inside an XSpice session) are going
> to use libusb to access the USB devices.
> 
> So then the question - why not modify libusb to detect devices from the
> unix domain socket instead of making the round trip through the kernel?
>  It has the benefit of letting you keep the traffic and the files in
> userspace, and avoiding sharing devices system wide.  The main downside
> would seem to be that non libusb devices (e.g. thumb drives et all)
> would not be supported.  For our use case, that limitation is not an
> issue, and the simplicity is compelling.
> 
> I wanted to share this idea to make sure there wasn't something else we
> were missing and to see what others think.
> 
> Thoughts and comments are appreciated.
> 
> Cheers,
> 
> Jeremy
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