[RFC][PATCH 2/9] usb: gadget: add usb_gadget_start/stop()

[Roger Quadros <rogerq@ti.com>]

The OTG state machine needs a mechanism to start and
stop the gadget controller. Add usb_gadget_start()
and usb_gadget_stop().

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
 drivers/usb/gadget/udc/udc-core.c | 166 +++++++++++++++++++++++++++++++++++---
 include/linux/usb/gadget.h        |   3 +
 2 files changed, 158 insertions(+), 11 deletions(-)

diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
index 5a81cb0..69b4123 100644
--- a/drivers/usb/gadget/udc/udc-core.c
+++ b/drivers/usb/gadget/udc/udc-core.c
@@ -35,6 +35,8 @@
  * @dev - the child device to the actual controller
  * @gadget - the gadget. For use by the class code
  * @list - for use by the udc class driver
+ * @running - udc is running
+ * @softconnect - sysfs softconnect says OK to connect
  *
  * This represents the internal data structure which is used by the UDC-class
  * to hold information about udc driver and gadget together.
@@ -44,6 +46,8 @@ struct usb_udc {
 	struct usb_gadget		*gadget;
 	struct device			dev;
 	struct list_head		list;
+	bool				running;
+	bool				softconnect;
 };
 
 static struct class *udc_class;
@@ -187,7 +191,14 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
  */
 static inline int usb_gadget_udc_start(struct usb_udc *udc)
 {
-	return udc->gadget->ops->udc_start(udc->gadget, udc->driver);
+	int ret;
+
+	dev_dbg(&udc->dev, "%s\n", __func__);
+	ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
+	if (!ret)
+		udc->running = 1;
+
+	return ret;
 }
 
 /**
@@ -204,10 +215,140 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
  */
 static inline void usb_gadget_udc_stop(struct usb_udc *udc)
 {
+	dev_dbg(&udc->dev, "%s\n", __func__);
 	udc->gadget->ops->udc_stop(udc->gadget);
+	udc->running = 0;
 }
 
 /**
+ * usb_udc_start - Start the usb device controller only if conditions met
+ * @udc: The UDC to be started
+ *
+ * Start the UDC and connect to bus (enable pull) only if the
+ * following conditions are met
+ * - UDC is not already running
+ * - gadget function driver is loaded
+ * - userspace softconnect says OK to connect
+ *
+ * NOTE: udc_lock must be held by caller.
+ *
+ * Returs 0 on success or not ready to start, else negative errno.
+ */
+static int usb_udc_start(struct usb_udc *udc)
+{
+	int ret;
+
+	if (udc->running) {
+		dev_err(&udc->dev, "%s: not starting as already running\n",
+			__func__);
+		return -EBUSY;
+	}
+
+	if (udc->driver && udc->softconnect) {
+		ret = usb_gadget_udc_start(udc);
+		if (ret)
+			return ret;
+
+		usb_gadget_connect(udc->gadget);
+	}
+
+	return 0;
+}
+
+/**
+ * usb_udc_stop - Stop the usb device controller
+ * @udc: The UDC to be stopped
+ *
+ * Disconnect from bus (disable pull) and stop the UDC.
+ *
+ * NOTE: udc_lock must be held by caller.
+ *
+ * Returs 0 on success, else negative errno.
+ */
+static int usb_udc_stop(struct usb_udc *udc)
+{
+	if (!udc->running) {
+		dev_err(&udc->dev, "%s: not stopping as already halted\n",
+			__func__);
+		return -EBUSY;
+	}
+
+	usb_gadget_disconnect(udc->gadget);
+	udc->driver->disconnect(udc->gadget);
+	usb_gadget_udc_stop(udc);
+
+	return 0;
+}
+
+/**
+ * usb_gadget_start - start the usb gadget controller
+ * @gadget: the gadget device to start
+ *
+ * This is external API for use by OTG core.
+ *
+ * Start the usb device controller and connect to bus (enable pull).
+ * There is no guarantee that the controller is started
+ * as we might be missing some dependencies
+ * i.e. gadget function driver not loaded or softconnect disabled.
+ */
+int usb_gadget_start(struct usb_gadget *gadget)
+{
+	int ret;
+	struct usb_udc *udc = NULL;
+
+	dev_dbg(&gadget->dev, "%s\n", __func__);
+	mutex_lock(&udc_lock);
+	list_for_each_entry(udc, &udc_list, list)
+		if (udc->gadget == gadget)
+			goto found;
+
+	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
+		__func__);
+	mutex_unlock(&udc_lock);
+	return -EINVAL;
+
+found:
+	ret = usb_udc_start(udc);
+	mutex_unlock(&udc_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_gadget_start);
+
+/**
+ * usb_gadget_stop - stop the usb gadget
+ * @gadget: The gadget device we want to stop
+ *
+ * This is external API for use by OTG core.
+ *
+ * Disconnect from the bus (disable pull) and stop the
+ * gadget controller.
+ */
+int usb_gadget_stop(struct usb_gadget *gadget)
+{
+	int ret;
+	struct usb_udc *udc = NULL;
+
+	dev_dbg(&gadget->dev, "%s\n", __func__);
+	mutex_lock(&udc_lock);
+	list_for_each_entry(udc, &udc_list, list)
+		if (udc->gadget == gadget)
+			goto found;
+
+	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
+		__func__);
+	mutex_unlock(&udc_lock);
+	return -EINVAL;
+
+found:
+	ret = usb_udc_stop(udc);
+	mutex_unlock(&udc_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_gadget_stop);
+
+/**
  * usb_udc_release - release the usb_udc struct
  * @dev: the dev member within usb_udc
  *
@@ -278,6 +419,7 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
 		goto err3;
 
 	udc->gadget = gadget;
+	udc->softconnect = 1;	/* connect by default */
 
 	mutex_lock(&udc_lock);
 	list_add_tail(&udc->list, &udc_list);
@@ -329,10 +471,8 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
 
 	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
 
-	usb_gadget_disconnect(udc->gadget);
-	udc->driver->disconnect(udc->gadget);
+	usb_udc_stop(udc);
 	udc->driver->unbind(udc->gadget);
-	usb_gadget_udc_stop(udc);
 
 	udc->driver = NULL;
 	udc->dev.driver = NULL;
@@ -378,6 +518,7 @@ EXPORT_SYMBOL_GPL(usb_del_gadget_udc);
 
 /* ------------------------------------------------------------------------- */
 
+/* udc_lock must be held */
 static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *driver)
 {
 	int ret;
@@ -392,12 +533,12 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
 	ret = driver->bind(udc->gadget, driver);
 	if (ret)
 		goto err1;
-	ret = usb_gadget_udc_start(udc);
+
+	ret = usb_udc_start(udc);
 	if (ret) {
 		driver->unbind(udc->gadget);
 		goto err1;
 	}
-	usb_gadget_connect(udc->gadget);
 
 	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
 	return 0;
@@ -510,12 +651,15 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
 	}
 
 	if (sysfs_streq(buf, "connect")) {
-		usb_gadget_udc_start(udc);
-		usb_gadget_connect(udc->gadget);
+		mutex_lock(&udc_lock);
+		udc->softconnect = 1;
+		usb_udc_start(udc);
+		mutex_unlock(&udc_lock);
 	} else if (sysfs_streq(buf, "disconnect")) {
-		usb_gadget_disconnect(udc->gadget);
-		udc->driver->disconnect(udc->gadget);
-		usb_gadget_udc_stop(udc);
+		mutex_lock(&udc_lock);
+		udc->softconnect = 0;
+		usb_udc_stop(udc);
+		mutex_unlock(&udc_lock);
 	} else {
 		dev_err(dev, "unsupported command '%s'\n", buf);
 		return -EINVAL;
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index e2f00fd..7ada7e6 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -922,6 +922,9 @@ int usb_gadget_probe_driver(struct usb_gadget_driver *driver);
  */
 int usb_gadget_unregister_driver(struct usb_gadget_driver *driver);
 
+int usb_gadget_start(struct usb_gadget *gadget);
+int usb_gadget_stop(struct usb_gadget *gadget);
+
 extern int usb_add_gadget_udc_release(struct device *parent,
 		struct usb_gadget *gadget, void (*release)(struct device *dev));
 extern int usb_add_gadget_udc(struct device *parent, struct usb_gadget *gadget);
-- 
2.1.0