[Bug 787091] Re: Unable to use USB device in KVM quest

[Serge Hallyn]

Let's see if we can get root in general to fail to open this.  First
paste the following into 'open.c' (without the '========' lines), and
then compile that using 'make open'.

===============================================================
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int main(int argc, char *argv[])
{
	int ret;
	
	if (argc < 2) 
	{
		printf("try %s /dev/bus/usb/001/013\n", argv[0]);
		exit(1);
	}
	ret = open(argv[1], O_RDWR|O_NONBLOCK);
	printf("open returned %d\n", ret);
	close(ret);
}
===============================================================

Plug in the printer and try starting the VM with libvirt.  Look in the
log file to get the pathname it is trying to use.  Then run open with
that file as argument.  For instance if you see

/dev/bus/usb/001/004: Operation not permitted

then try

  sudo ./open /dev/bus/usb/001/004

If it says it returned a positive number, then it succeeded in opening
it.  If it returned -1, then we know that in fact root can't open that
device, and it isn't just libvirt.

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https://bugs.launchpad.net/bugs/787091

Title:
  Unable to use USB device in KVM quest

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