staging: comedi: comedi_fops: send SIGIO according to command direction

`comedi_event()` is called from low-level drivers to handle comedi
asynchronous command event flags.  Some events cause waiting tasks to be
woken up, and a `SIGIO` signal to be sent via `kill_fasync()`.  The
signal code is `POLL_OUT` if the subdevice supports commands in the
"write" direction, or `POLL_IN` for the "read" direction.  If the
subdevice supports commands in either direction, it sends two `SIGIO`
signals, one with each code.  Change that latter case to only send one
`SIGIO` signal, using the direction of the current command to determine
the signal code.  If the `CMDF_WRITE` flag is set in the current
command, it's in the "write" direction, otherwise it's in the "read"
direction.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_fops.c

@@ -2674,11 +2674,11 @@ void comedi_event(struct comedi_device *dev, struct comedi_subdevice *s)
 	}
 
 	if (async->cb_mask & events) {
+		int si_code;
+
 		wake_up_interruptible(&async->wait_head);
-		if (s->subdev_flags & SDF_CMD_READ)
-			kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
-		if (s->subdev_flags & SDF_CMD_WRITE)
-			kill_fasync(&dev->async_queue, SIGIO, POLL_OUT);
+		si_code = async->cmd.flags & CMDF_WRITE ? POLL_OUT : POLL_IN;
+		kill_fasync(&dev->async_queue, SIGIO, si_code);
 	}
 }
 EXPORT_SYMBOL_GPL(comedi_event);