USB: Remove restrictions on signal numbers in devio.c

Just over a year ago (!) I had this brief exchange with Alan Stern:

>> It seems that the signal that can be used with USBDEVFS_DISCSIGNAL and
>> in usbdevfs_urb.signr is limited to the real-time signals SIGRTMIN to
>> SIGRTMAX. What's the rationale for this restriction? I believe that a
>> process can kill() itself with any signal number, can't it? I was
>> planning to use SIGIO for usbdevfs_urb.signr and SIGTERM (uncaught) for
>> USBDEVFS_DISCSIGNAL. I don't think I'll have a problem with using
>> SIGRTMIN+n instead, but I'm curious to know if there's some subtle
>> problem with the non-real-time signals that I should be aware of.
>
> I don't know of any reason for this restriction.

Since no-one else could think of a reason either, I offer the following
patch which allows any signal to be used with USBDEVFS_DISCSIGNAL and
usbdevfs_urb.signr.

Signed-off-by: Phil Endecott <[e-mail]>
Cc: Alan Stern <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/devio.c

···
 		return -EINVAL;
 	if (!uurb->buffer)
 		return -EINVAL;
-	if (uurb->signr != 0 && (uurb->signr < SIGRTMIN ||
-				 uurb->signr > SIGRTMAX))
-		return -EINVAL;
 	if (!(uurb->type == USBDEVFS_URB_TYPE_CONTROL &&
 	    (uurb->endpoint & ~USB_ENDPOINT_DIR_MASK) == 0)) {
 		ifnum = findintfep(ps->dev, uurb->endpoint);
···
 
 	if (copy_from_user(&ds, arg, sizeof(ds)))
 		return -EFAULT;
-	if (ds.signr != 0 && (ds.signr < SIGRTMIN || ds.signr > SIGRTMAX))
-		return -EINVAL;
 	ps->discsignr = ds.signr;
 	ps->disccontext = ds.context;
 	return 0;