USB: otg: add otg id notifier utiltiies

Add a otg_id notifier to allow multiple drivers to cooperate to
determine the type of cable connected to a USB connector without
requiring direct calls between the drivers.

Change-Id: Ic5675f1a89daf85b17336765de24e4bdb6df6348
Signed-off-by: Colin Cross <ccross@android.com>

drivers/usb/otg/Makefile

@@ -8,6 +8,7 @@ ccflags-$(CONFIG_USB_GADGET_DEBUG)	+= -DDEBUG
 # infrastructure
 obj-$(CONFIG_USB_OTG_UTILS)	+= otg.o
 obj-$(CONFIG_USB_OTG_WAKELOCK)	+= otg-wakelock.o
+obj-$(CONFIG_USB_OTG_UTILS)	+= otg_id.o
 
 # transceiver drivers
 obj-$(CONFIG_USB_GPIO_VBUS)	+= gpio_vbus.o

drivers/usb/otg/otg_id.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Author:
+ *	Colin Cross <ccross@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include <linux/usb/otg_id.h>
+
+static DEFINE_MUTEX(otg_id_lock);
+static struct plist_head otg_id_plist =
+	PLIST_HEAD_INIT(otg_id_plist);
+static struct otg_id_notifier_block *otg_id_active;
+static bool otg_id_cancelling;
+static bool otg_id_inited;
+
+static void otg_id_cancel(void)
+{
+	if (otg_id_active) {
+		otg_id_cancelling = true;
+		mutex_unlock(&otg_id_lock);
+
+		otg_id_active->cancel(otg_id_active);
+
+		mutex_lock(&otg_id_lock);
+		otg_id_cancelling = false;
+	}
+}
+
+static void __otg_id_notify(void)
+{
+	int ret;
+	struct otg_id_notifier_block *otg_id_nb;
+
+	if (plist_head_empty(&otg_id_plist))
+		return;
+
+	plist_for_each_entry(otg_id_nb, &otg_id_plist, p) {
+		ret = otg_id_nb->detect(otg_id_nb);
+		if (ret == OTG_ID_HANDLED) {
+			otg_id_active = otg_id_nb;
+			return;
+		}
+	}
+
+	WARN(1, "otg id event not handled");
+	otg_id_active = NULL;
+}
+
+int otg_id_init(void)
+{
+	mutex_lock(&otg_id_lock);
+
+	otg_id_inited = true;
+	__otg_id_notify();
+
+	mutex_unlock(&otg_id_lock);
+	return 0;
+}
+late_initcall(otg_id_init);
+
+/**
+ * otg_id_register_notifier
+ * @otg_id_nb: notifier block containing priority and callback function
+ *
+ * Register a notifier that will be called on any USB cable state change.
+ * The priority determines the order the callback will be called in, a higher
+ * number will be called first.  A callback function needs to determine the
+ * type of USB cable that is connected.  If it can determine the type, it
+ * should notify the appropriate drivers (for example, call an otg notifier
+ * with USB_EVENT_VBUS), and return OTG_ID_HANDLED.  Once a callback has
+ * returned OTG_ID_HANDLED, it is responsible for calling otg_id_notify() when
+ * the detected USB cable is disconnected.
+ */
+int otg_id_register_notifier(struct otg_id_notifier_block *otg_id_nb)
+{
+	plist_node_init(&otg_id_nb->p, otg_id_nb->priority);
+
+	mutex_lock(&otg_id_lock);
+	plist_add(&otg_id_nb->p, &otg_id_plist);
+
+	if (otg_id_inited) {
+		otg_id_cancel();
+		__otg_id_notify();
+	}
+
+	mutex_unlock(&otg_id_lock);
+
+	return 0;
+}
+
+void otg_id_unregister_notifier(struct otg_id_notifier_block *otg_id_nb)
+{
+	mutex_lock(&otg_id_lock);
+
+	plist_del(&otg_id_nb->p, &otg_id_plist);
+
+	if (otg_id_inited && (otg_id_active == otg_id_nb)) {
+		otg_id_cancel();
+		__otg_id_notify();
+	}
+
+	mutex_unlock(&otg_id_lock);
+}
+
+/**
+ * otg_id_notify
+ *
+ * Notify listeners on any USB cable state change.
+ *
+ * A driver may only call otg_id_notify if it returned OTG_ID_HANDLED the last
+ * time it's notifier was called, and it's cancel function has not been called.
+ */
+void otg_id_notify(void)
+{
+	mutex_lock(&otg_id_lock);
+
+	if (otg_id_cancelling)
+		goto out;
+
+	__otg_id_notify();
+
+out:
+	mutex_unlock(&otg_id_lock);
+}

include/linux/usb/otg_id.h

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2011 Google, Inc.
+ *
+ * Author:
+ *	Colin Cross <ccross@android.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __LINUX_USB_OTG_ID_H
+#define __LINUX_USB_OTG_ID_H
+
+#include <linux/notifier.h>
+#include <linux/plist.h>
+
+/**
+ * otg_id_notifier_block
+ *
+ * @priority: Order the notifications will be called in.  Higher numbers
+ *    get called first.
+ * @detect: Called during otg_id_notify.  Return OTG_ID_HANDLED if the USB cable
+ *    has been identified
+ * @cancel: Called after detect has returned OTG_ID_HANDLED to ask it to
+ *    release detection resources to allow a new identification to occur.
+ */
+
+struct otg_id_notifier_block {
+	int priority;
+	int (*detect)(struct otg_id_notifier_block *otg_id_nb);
+	void (*cancel)(struct otg_id_notifier_block *otg_id_nb);
+	struct plist_node p;
+};
+
+#define OTG_ID_HANDLED 1
+#define OTG_ID_UNHANDLED 0
+
+int otg_id_register_notifier(struct otg_id_notifier_block *otg_id_nb);
+void otg_id_unregister_notifier(struct otg_id_notifier_block *otg_id_nb);
+
+void otg_id_notify(void);
+
+#endif /* __LINUX_USB_OTG_ID_H */