staging: comedi: add generic auto-config functions

Add (and export) generic auto-config function `comedi_auto_config()` to
allow hardware devices on arbitrary bus types (e.g. platform devices,
spi devices, etc.) to be auto-configured as comedi devices.  This uses a
new `auto_attach()` hook in the `struct comedi_driver`.  This new hook
will eventually replace the bus-specific `attach_pci()` and
`attach_usb()` hooks in the low-level comedi drivers.

When the `auto_attach()` hook is called in the low-level driver, the
`hw_dev` member of the `struct comedi_device` will have already been set
to the hardware device passed to `comedi_auto_config()`.  The low-level
driver can convert this to some bus-device wrapper structure pointer,
possibly with the help of the `context` parameter that is passed
unchanged from the `comedi_auto_config()` call.

Also export the existing `comedi_auto_unconfig()` function as the
matching call to `comedi_auto_config()`.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedidev.h

@@ -204,6 +204,7 @@ struct comedi_driver {
 	void (*detach) (struct comedi_device *);
 	int (*attach_pci) (struct comedi_device *, struct pci_dev *);
 	int (*attach_usb) (struct comedi_device *, struct usb_interface *);
+	int (*auto_attach) (struct comedi_device *, unsigned long);
 
 	/* number of elements in board_name and board_id arrays */
 	unsigned int num_names;
@@ -510,6 +511,9 @@ static inline void *comedi_aux_data(int options[], int n)
 int comedi_alloc_subdevice_minor(struct comedi_device *dev,
 				 struct comedi_subdevice *s);
 void comedi_free_subdevice_minor(struct comedi_subdevice *s);
+int comedi_auto_config(struct device *hardware_device,
+		       struct comedi_driver *driver, unsigned long context);
+void comedi_auto_unconfig(struct device *hardware_device);
 int comedi_pci_auto_config(struct pci_dev *pcidev,
 			   struct comedi_driver *driver);
 void comedi_pci_auto_unconfig(struct pci_dev *pcidev);

drivers/staging/comedi/drivers.c

@@ -922,7 +922,27 @@ static int comedi_old_auto_config(struct device *hardware_device,
 					 (unsigned long)&it);
 }
 
-static void comedi_auto_unconfig(struct device *hardware_device)
+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)
 {
 	int minor;
 
@@ -934,6 +954,7 @@ static void comedi_auto_unconfig(struct device *hardware_device)
 	BUG_ON(minor >= COMEDI_NUM_BOARD_MINORS);
 	comedi_free_board_minor(minor);
 }
+EXPORT_SYMBOL_GPL(comedi_auto_unconfig);
 
 /**
  * comedi_pci_enable() - Enable the PCI device and request the regions.