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

[Hans de Goede]

Hi,

On 04/14/2015 09:10 PM, Jeremy White wrote:
> Hey Hans,
>
>> "most Linux applications ... are going to use libusb to access the USB
>> devices."
>>
>> That is not true, applications using libusb rather then a kernel driver
>> are the exception not the rule. Basically the only major applications using
>> libusb are sane (scanners) and libgphoto2 (still photo cameras), anything
>> else, webcams, usb audio, hid devices, usb-sticks, usb-harddisks, dvb
>> receivers,
>> printers (*), etc. is all using kernel drivers.
>
> Thanks for the reply; it's evident I don't have a vivid imagination for
> the world of USB devices :-/.
>
>>
>> *) Yes some printer backends may use libusb, this is usually done to get
>> some extra info from the printer using vendor specific commands, the actual
>> printing is usually still done via /dev/lp and thus through a kernel
>> driver.
>
> Are you sure?  A (perhaps naive) look at the CUPS source code strongly
> suggests that most usb device access now goes through libusb for CUPS.

Last time I was helping a printer driver developer with usb problems
what I wrote above was true, but I'm not 100% sure.

Regards,

Hans