Re: failing to force-claim USB interface

[David Brownell <david-b@pacbell.net>]

> I am trying to make use of the usbfs USBDEVFS_DISCONNECT ioctl, and
> I am failing.

Appended, see a snippet of code which worked reliably way back on
the original 2.4 patch.  Maybe you tripped on the precondition?
Or maybe this is just broken so far in 2.6.

A fair amount of usbfs code is at least slightly broken in 2.6;
some usbcore driver model changes are still needed in the area
of this particular ioctl.  (Which got mangled more than most
during its evolution.)  Was this with a 2.6.1 kernel?

I'm thinking this kind of thing ought to be generically doable
with sysfs, maybe with symlink/unlink syscalls between device
and driver nodes.

- Dave


     if (ioctl (fd, USBDEVFS_CLAIMINTERFACE, &ifno) < 0) {
#ifdef  USBDEVFS_DISCONNECT
         int                             saved_errno = errno;
         struct usbdevfs_ioctl           command;
         int                             retval;

         /*
          * maybe we need to boot a kernel driver off before we
          * can bind to this.  a "polite" unbind might be nice;
          * for now we expect apps to adopt a reasonble policy,
          * checking if it's claimed already (when it matters).
          */
         if (saved_errno != EBUSY)
             return -errno;
         command.ifno = ifno;
         command.ioctl_code = USBDEVFS_DISCONNECT;
         command.data = 0;
         retval = ioctl (fd, USBDEVFS_IOCTL, &command);
         if (retval < 0)
             return -saved_errno;

         if (ioctl (fd, USBDEVFS_CLAIMINTERFACE, &ifno) < 0)
             return -errno;
#else
         return -errno;
#endif
     }
     return 0;