HID: wiimote: add sub-device module infrastructure

To avoid loading all sub-device drivers for every Wii Remote, even though
the required hardware might not be available, we introduce a module layer.

The module layer specifies which sub-devices are available on each
device-type. After device detection, we only load the modules for the
detected device. If module loading fails, we unload everything and mark
the device as WIIMOTE_DEV_UNKNOWN. As long as a device is marked as
"unknown", no sub-devices will be used and the device is considered
unsupported.

All the different sub-devices, including KEYS, RUMBLE, BATTERY, LEDS,
ACCELEROMETER, IR and more will be ported in follow-up patches to the new
module layer.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-wiimote-modules.c

@@ -0,0 +1,45 @@
+/*
+ * Device Modules for Nintendo Wii / Wii U HID Driver
+ * Copyright (c) 2011-2013 David Herrmann <dh.herrmann@gmail.com>
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+/*
+ * Wiimote Modules
+ * Nintendo devices provide different peripherals and many new devices lack
+ * initial features like the IR camera. Therefore, each peripheral device is
+ * implemented as an independent module and we probe on each device only the
+ * modules for the hardware that really is available.
+ *
+ * Module registration is sequential. Unregistration is done in reverse order.
+ * After device detection, the needed modules are loaded. Users can trigger
+ * re-detection which causes all modules to be unloaded and then reload the
+ * modules for the new detected device.
+ *
+ * wdata->input is a shared input device. It is always initialized prior to
+ * module registration. If at least one registered module is marked as
+ * WIIMOD_FLAG_INPUT, then the input device will get registered after all
+ * modules were registered.
+ * Please note that it is unregistered _before_ the "remove" callbacks are
+ * called. This guarantees that no input interaction is done, anymore. However,
+ * the wiimote core keeps a reference to the input device so it is freed only
+ * after all modules were removed. It is safe to send events to unregistered
+ * input devices.
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/spinlock.h>
+#include "hid-wiimote.h"
+
+/* module table */
+
+const struct wiimod_ops *wiimod_table[WIIMOD_NUM] = {
+};