[2/2] USB: usbdevfs: restore warning for nonsensical flags

[Oliver Neukum <oneukum@suse.com>]

On Mi, 2018-09-05 at 15:07 +0200, Greg KH wrote:
> On Wed, Sep 05, 2018 at 03:02:48PM +0200, Oliver Neukum wrote:
> > On Mi, 2018-09-05 at 14:19 +0200, Greg KH wrote:
> > > On Wed, Sep 05, 2018 at 12:07:03PM +0200, Oliver Neukum wrote:

> > > > +	if (!allow_short && uurb->flags & USBDEVFS_URB_SHORT_NOT_OK)
> > > > +		dev_warn(&ps->dev->dev, "Requested nonsensical USBDEVFS_URB_SHORT_NOT_OK.\n");
> > > > +	if (!allow_zero && uurb->flags & USBDEVFS_URB_ZERO_PACKET)
> > > > +		dev_warn(&ps->dev->dev, "Requested nonsensical USBDEVFS_URB_ZERO_PACKET.\n");
> > > 
> > > We should not make it trivial for userspace to spam the kernel log if at
> > > all possible.  Returning an error is probably the better thing to do
> > > here, not just silently fix it up or ignore it.
> > 
> > That means a change in the API in a way that makes orking systems fail.
> 
> Ah, good point.

Well, but do we want to do this in the next major release even if we
cannot do it in a stable release?

>   I guess they were hitting the same dev_WARN() messages
> today anyway, right?

Yes. And for a kernel problem you really want the stack traces.
Still, that does not tell us that we want to print a message if
user space messes up. So dev_warn() or nothing?

> > Do you want an extra version for stable?
> 
> No, but why was this patch not marked for stable?

I was under the impression that it was. This is a separate
patch because you could argue that it is unnecessary or that stable
and the next release should diverge on whether to take it.

	Regards
		Oliver