HID: wiimote: Add extension support stub

The wiimote supports several extensions. This adds a separate source file which
handles all extensions and can be disabled at compile-time.

The driver reacts on "plug"-events on the extension port and starts a worker
which initializes or deinitializes the extensions.

Currently, the initialization logic is not fully understood and we can only
detect and enable all extensions when all extensions are deactivated. Therefore,
we need to disable all extensions, then detect and activate them again to react
on "plug"-events.
However, deactivating extensions will generate a new "plug"-event and we will
never leave that loop. Hence, we only support extensions if they are plugged
before the wiimote is connected (or before the ext-input device is opened). In
the future we may support full extension hotplug support, but
reverse-engineering this may take a while.

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

1 files changed, 130 insertions, 0 deletions

diff --git a/drivers/hid/hid-wiimote-ext.c b/drivers/hid/hid-wiimote-ext.c
new file mode 100644
index 000000000000..fa9c67722aca
--- /dev/null
+++ b/drivers/hid/hid-wiimote-ext.c
@@ -0,0 +1,130 @@
+/*
+ * HID driver for Nintendo Wiimote extension devices
+ * Copyright (c) 2011 David Herrmann
+ */
+
+/*
+ * 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.
+ */
+
+#include <linux/atomic.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include "hid-wiimote.h"
+
+struct wiimote_ext {
+	struct wiimote_data *wdata;
+	struct work_struct worker;
+
+	atomic_t opened;
+	atomic_t mp_opened;
+	bool plugged;
+	bool motionp;
+	__u8 ext_type;
+};
+
+enum wiiext_type {
+	WIIEXT_NONE,		/* placeholder */
+	WIIEXT_CLASSIC,		/* Nintendo classic controller */
+	WIIEXT_NUNCHUCK,	/* Nintendo nunchuck controller */
+};
+
+static void wiiext_worker(struct work_struct *work)
+{
+	struct wiimote_ext *ext = container_of(work, struct wiimote_ext,
+									worker);
+}
+
+/* schedule work only once, otherwise mark for reschedule */
+static void wiiext_schedule(struct wiimote_ext *ext)
+{
+	queue_work(system_nrt_wq, &ext->worker);
+}
+
+/*
+ * Reacts on extension port events
+ * Whenever the driver gets an event from the wiimote that an extension has been
+ * plugged or unplugged, this funtion shall be called. It checks what extensions
+ * are connected and initializes and activates them.
+ * This can be called in atomic context. The initialization is done in a
+ * separate worker thread. The state.lock spinlock must be held by the caller.
+ */
+void wiiext_event(struct wiimote_data *wdata, bool plugged)
+{
+	if (!wdata->ext)
+		return;
+
+	if (wdata->ext->plugged == plugged)
+		return;
+
+	wdata->ext->plugged = plugged;
+	/*
+	 * We need to call wiiext_schedule(wdata->ext) here, however, the
+	 * extension initialization logic is not fully understood and so
+	 * automatic initialization is not supported, yet.
+	 */
+}
+
+/*
+ * Returns true if the current DRM mode should contain extension data and false
+ * if there is no interest in extension data.
+ * All supported extensions send 6 byte extension data so any DRM that contains
+ * extension bytes is fine.
+ * The caller must hold the state.lock spinlock.
+ */
+bool wiiext_active(struct wiimote_data *wdata)
+{
+	if (!wdata->ext)
+		return false;
+
+	return wdata->ext->motionp || wdata->ext->ext_type;
+}
+
+/* Initializes the extension driver of a wiimote */
+int wiiext_init(struct wiimote_data *wdata)
+{
+	struct wiimote_ext *ext;
+	unsigned long flags;
+
+	ext = kzalloc(sizeof(*ext), GFP_KERNEL);
+	if (!ext)
+		return -ENOMEM;
+
+	ext->wdata = wdata;
+	INIT_WORK(&ext->worker, wiiext_worker);
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->ext = ext;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	return 0;
+}
+
+/* Deinitializes the extension driver of a wiimote */
+void wiiext_deinit(struct wiimote_data *wdata)
+{
+	struct wiimote_ext *ext = wdata->ext;
+	unsigned long flags;
+
+	if (!ext)
+		return;
+
+	/*
+	 * We first unset wdata->ext to avoid further input from the wiimote
+	 * core. The worker thread does not access this pointer so it is not
+	 * affected by this.
+	 * We kill the worker after this so it does not get respawned during
+	 * deinitialization.
+	 */
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->ext = NULL;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	cancel_work_sync(&ext->worker);
+	kfree(ext);
+}