staging: comedi: drivers: introduce comedi_legacy_detach()

This function is intended to be used by the comedi legacy (ISA) drivers
either directly as the (*detach) function or as a helper in the drivers
private (*detach) function.

Modify the comedi_request_region() helper so that it stores the 'len' of
the region as well as the 'start' after the region has been successfuly
allocated by request_region() in __comedi_request_region(). This region
will then be automatically released detach of the driver by the
comedi_legacy_detach() helper.

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

@@ -216,6 +216,7 @@ struct comedi_device {
 
 	/* dumb */
 	unsigned long iobase;
+	unsigned long iolen;
 	unsigned int irq;
 
 	struct comedi_subdevice *read_subdev;
@@ -354,6 +355,7 @@ int __comedi_request_region(struct comedi_device *,
 			    unsigned long start, unsigned long len);
 int comedi_request_region(struct comedi_device *,
 			  unsigned long start, unsigned long len);
+void comedi_legacy_detach(struct comedi_device *);
 
 int comedi_auto_config(struct device *, struct comedi_driver *,
 		       unsigned long context);

drivers/staging/comedi/drivers.c

@@ -122,6 +122,7 @@ static void cleanup_device(struct comedi_device *dev)
 	dev->board_name = NULL;
 	dev->board_ptr = NULL;
 	dev->iobase = 0;
+	dev->iolen = 0;
 	dev->ioenabled = false;
 	dev->irq = 0;
 	dev->read_subdev = NULL;
@@ -387,13 +388,29 @@ int comedi_request_region(struct comedi_device *dev,
 	int ret;
 
 	ret = __comedi_request_region(dev, start, len);
-	if (ret == 0)
+	if (ret == 0) {
 		dev->iobase = start;
+		dev->iolen = len;
+	}
 
 	return ret;
 }
 EXPORT_SYMBOL_GPL(comedi_request_region);
 
+/**
+ * comedi_legacy_detach() - A generic (*detach) function for legacy drivers.
+ * @dev: comedi_device struct
+ */
+void comedi_legacy_detach(struct comedi_device *dev)
+{
+	if (dev->iobase && dev->iolen) {
+		release_region(dev->iobase, dev->iolen);
+		dev->iobase = 0;
+		dev->iolen = 0;
+	}
+}
+EXPORT_SYMBOL_GPL(comedi_legacy_detach);
+
 int comedi_device_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	struct comedi_driver *driv;