[openib-general] IB/ipath - initialize diagpkt file on device init only

[Roland Dreier]

I tried loading ib_ipath on one of my systems without an ipath device,
and I got the message

    ib_ipath: Could not create class_dev for minor 127, ipath_diagpkt (err 19)

but I couldn't reproduce the hang of modprobe.

Anyway, taking a quick look at what caused that message showed that
the problem is that ipath_class is NULL there.  And that makes sense,
because ipath_class isn't created until ipath_user_add() is called in
ipath_init_one() (which is never called if there are no devices).

So I think a correct fix is to move any global initialization like
creating ipath_class into the module_init function before probing any
devices.  I don't approve of this latest patch because you do this:

 > -int __init ipath_diagpkt_add(void)
 > -{
 > -	return ipath_cdev_init(IPATH_DIAGPKT_MINOR,
 > -			       "ipath_diagpkt", &diagpkt_file_ops,
 > -			       &diagpkt_cdev, &diagpkt_class_dev);
 > -}

 > +void ipath_diagpkt_add(void)
 > +{
 > +	if (atomic_inc_return(&diagpkt_count) == 1)
 > +		ipath_cdev_init(IPATH_DIAGPKT_MINOR,
 > +				"ipath_diagpkt", &diagpkt_file_ops,
 > +				&diagpkt_cdev, &diagpkt_class_dev);
 > +}

which means that you've stopped checking the return value of
ipath_cdev_init().  What will happen if it fails?  I would guess
everything blows up, right?

 - R.