staging: comedi: add 'pacer' member to struct comedi_device

Add a new member to the comedi_device struct for a comedi_8254 'pacer'. This
provides a convient place to store the data allocated by the comedi_8254 module
for boards that use an 8254 device to create the data acquisition pacer clock.

Automatically free this pointer in comedi_device_detach_cleanup() so that the
drivers don't need to do it when then are detached.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -256,6 +256,7 @@ struct comedi_driver {
 struct comedi_device {
 	int use_count;
 	struct comedi_driver *driver;
+	struct comedi_8254 *pacer;
 	void *private;
 
 	struct device *class_dev;

drivers/staging/comedi/drivers.c

@@ -139,7 +139,9 @@ static void comedi_device_detach_cleanup(struct comedi_device *dev)
 		dev->n_subdevices = 0;
 	}
 	kfree(dev->private);
+	kfree(dev->pacer);
 	dev->private = NULL;
+	dev->pacer = NULL;
 	dev->driver = NULL;
 	dev->board_name = NULL;
 	dev->board_ptr = NULL;