staging: comedi: simplify comedi_auto_attach()

`comedi_auto_config()` just calls internal function
`comedi_auto_config_helper()`, passing it a wrapper function
`comedi_auto_config_wrapper()` to handle the specifics of checking and
calling the low-level comedi driver's `auto_attach()` handler.

Since there are no other callers of `comedi_auto_config_helper()` or
`comedi_auto_config_wrapper()`, combine everything into the single
exported function `comedi_auto_config()`.

Change the ordering of the check for existence of the low-level comedi
driver's `auto_attach()` handler and the allocation of the comedi minor
device number.  This means the log message warning of the absence of the
handler now has to be refer to the hardware device instead of the
not-yet-allocated comedi device.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers.c

@@ -833,12 +833,8 @@ void comedi_reset_async_buf(struct comedi_async *async)
 	async->events = 0;
 }
 
-static int
-comedi_auto_config_helper(struct device *hardware_device,
-			  struct comedi_driver *driver,
-			  int (*attach_wrapper) (struct comedi_device *,
-						 unsigned long),
-			  unsigned long context)
+int comedi_auto_config(struct device *hardware_device,
+		       struct comedi_driver *driver, unsigned long context)
 {
 	int minor;
 	struct comedi_device_file_info *dev_file_info;
@@ -848,6 +844,13 @@ comedi_auto_config_helper(struct device *hardware_device,
 	if (!comedi_autoconfig)
 		return 0;
 
+	if (!driver->auto_attach) {
+		dev_warn(hardware_device,
+			 "BUG! comedi driver '%s' has no auto_attach handler\n",
+			 driver->driver_name);
+		return -EINVAL;
+	}
+
 	minor = comedi_alloc_board_minor(hardware_device);
 	if (minor < 0)
 		return minor;
@@ -862,9 +865,8 @@ comedi_auto_config_helper(struct device *hardware_device,
 		ret = -EIO;
 	else {
 		comedi_set_hw_dev(comedi_dev, hardware_device);
-		/* set comedi_dev->driver here for attach wrapper */
 		comedi_dev->driver = driver;
-		ret = (*attach_wrapper)(comedi_dev, context);
+		ret = driver->auto_attach(comedi_dev, context);
 		if (ret < 0) {
 			module_put(driver->module);
 			__comedi_device_detach(comedi_dev);
@@ -878,25 +880,6 @@ comedi_auto_config_helper(struct device *hardware_device,
 		comedi_free_board_minor(minor);
 	return ret;
 }
-
-static int comedi_auto_config_wrapper(struct comedi_device *dev,
-				      unsigned long context)
-{
-	if (!dev->driver->auto_attach) {
-		dev_warn(dev->class_dev,
-			 "BUG! driver '%s' has no auto_attach handler\n",
-			 dev->driver->driver_name);
-		return -EINVAL;
-	}
-	return dev->driver->auto_attach(dev, context);
-}
-
-int comedi_auto_config(struct device *hardware_device,
-		       struct comedi_driver *driver, unsigned long context)
-{
-	return comedi_auto_config_helper(hardware_device, driver,
-					 comedi_auto_config_wrapper, context);
-}
 EXPORT_SYMBOL_GPL(comedi_auto_config);
 
 void comedi_auto_unconfig(struct device *hardware_device)