[PATCH 1/2] gadget: Introduce the usb charger framework

[Baolin Wang]

This patch introduces the usb charger driver based on usb gadget that
makes an enhancement to a power driver. It works well in practice but
that requires a system with suitable hardware.

The basic conception of the usb charger is that, when one usb charger
is added or removed by reporting from the usb gadget state change or
the extcon device state change, the usb charger will report to power
user to set the current limitation.

The usb charger will register notifiees on the usb gadget or the extcon
device to get notified the usb charger state.

Power user will register a notifiee on the usb charger to get notified
by status changes from the usb charger. It will report to power user
to set the current limitation when detecting the usb charger is added
or removed from extcon device state or usb gadget state.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
---
 drivers/usb/gadget/charger.c    |  547 +++++++++++++++++++++++++++++++++++++++
 include/linux/usb/usb_charger.h |  101 ++++++++
 2 files changed, 648 insertions(+)
 create mode 100644 drivers/usb/gadget/charger.c
 create mode 100644 include/linux/usb/usb_charger.h

diff --git a/drivers/usb/gadget/charger.c b/drivers/usb/gadget/charger.c
new file mode 100644
index 0000000..3ca0180
--- /dev/null
+++ b/drivers/usb/gadget/charger.c
@@ -0,0 +1,547 @@
+/*
+ * usb charger.c -- USB charger driver
+ *
+ * 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/device.h>
+#include <linux/err.h>
+#include <linux/extcon.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/usb_charger.h>
+
+#define DEFAULT_CUR_PROTECT	(50)
+#define DEFAULT_SDP_CUR_LIMIT	(500 - DEFAULT_CUR_PROTECT)
+#define DEFAULT_DCP_CUR_LIMIT	(1500 - DEFAULT_CUR_PROTECT)
+#define DEFAULT_CDP_CUR_LIMIT	(1500 - DEFAULT_CUR_PROTECT)
+#define DEFAULT_ACA_CUR_LIMIT	(1500 - DEFAULT_CUR_PROTECT)
+
+static LIST_HEAD(usb_charger_list);
+static DEFINE_MUTEX(usb_charger_list_lock);
+
+/*
+ * usb_charger_find_by_name - Get the usb charger device by name.
+ * @name - usb charger device name.
+ *
+ * notes: when this function walks the list and returns a charger
+ * it's dropped the lock which means that something else could come
+ * along and delete the charger before we dereference the pointer.
+ * It's very unlikely but it's a possibility so you should take care
+ * of it.
+ * Thus when you get the usb charger by name, you should call
+ * put_usb_charger() to derease the reference count of the usb charger.
+ *
+ * return the instance of usb charger device.
+ */
+struct usb_charger *usb_charger_find_by_name(char *name)
+{
+	struct usb_charger *uchger;
+
+	if (!name)
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&usb_charger_list_lock);
+	list_for_each_entry(uchger, &usb_charger_list, entry) {
+		if (!strcmp(uchger->name, name)) {
+			get_usb_charger(uchger);
+			mutex_unlock(&usb_charger_list_lock);
+			return uchger;
+		}
+	}
+	mutex_unlock(&usb_charger_list_lock);
+
+	return NULL;
+}
+
+/*
+ * usb_charger_register_notify() - Register a notifiee to get notified by
+ * 		any attach status changes from the usb charger type detection.
+ * @uchger - the usb charger device which is monitored.
+ * @nb - a notifier block to be registered.
+ */
+void usb_charger_register_notify(struct usb_charger *uchger,
+				 struct notifier_block *nb)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&uchger->lock, flags);
+	raw_notifier_chain_register(&uchger->uchger_nh, nb);
+	spin_unlock_irqrestore(&uchger->lock, flags);
+}
+
+/*
+ * usb_charger_unregister_notify() - Unregister a notifiee from the usb charger.
+ * @uchger - the usb charger device which is monitored.
+ * @nb - a notifier block to be unregistered.
+ */
+void usb_charger_unregister_notify(struct usb_charger *uchger,
+				   struct notifier_block *nb)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&uchger->lock, flags);
+	raw_notifier_chain_unregister(&uchger->uchger_nh, nb);
+	spin_unlock_irqrestore(&uchger->lock, flags);
+}
+
+/*
+ * usb_charger_register_extcon_notifier() - Register a notifiee of the usb
+ * 		charger to get notified by any attach status changes from
+ * 		the extcon device.
+ * @uchger - the usb charger device.
+ * @edev - the extcon device.
+ * @extcon_id - extcon id.
+ */
+int usb_charger_register_extcon_notifier(struct usb_charger *uchger,
+					 struct extcon_dev *edev,
+					 unsigned int extcon_id)
+{
+	if (!uchger || !edev)
+		return -EINVAL;
+
+	return extcon_register_notifier(edev, extcon_id, &uchger->extcon_nb.nb);
+}
+
+/*
+ * usb_charger_unregister_extcon_notifier() - Unregister a notifiee of the
+ * 		 usb charger from the extcon device.
+ * @uchger - the usb charger device.
+ * @edev - the extcon device.
+ * @extcon_id - extcon id.
+ */
+int usb_charger_unregister_extcon_notifier(struct usb_charger *uchger,
+					   struct extcon_dev *edev,
+					   unsigned int extcon_id)
+{
+	if (!uchger || !edev)
+		return -EINVAL;
+
+	return extcon_unregister_notifier(edev, extcon_id, &uchger->extcon_nb.nb);
+}
+
+/*
+ * usb_charger_register_gadget_notifier() - Register a notifiee of the usb
+ * 		charger to get notified by any attach status changes from
+ * 		the usb gadget device.
+ * @uchger - the usb charger device.
+ */
+int usb_charger_register_gadget_notifier(struct usb_charger *uchger)
+{
+	struct usb_gadget *ugadget = uchger->gadget;
+
+	return usb_gadget_register_notify(ugadget, &uchger->gadget_nb);
+}
+
+/*
+ * usb_charger_unregister_gadget_notifier() - Unregister a notifiee of the usb
+ * 		charger from the usb gadget device.
+ * @uchger - the usb charger device.
+ */
+int usb_charger_unregister_gadget_notifier(struct usb_charger *uchger)
+{
+	struct usb_gadget *ugadget = uchger->gadget;
+
+	return usb_gadget_unregister_notify(ugadget, &uchger->gadget_nb);
+}
+
+/*
+ * usb_charger_set_cur_limit() - Set the current limitation.
+ * @uchger - the usb charger device.
+ * @xxx_cur - the current limit by different charger type.
+ *
+ */
+int usb_charger_set_cur_limit(struct usb_charger *uchger,
+			      struct usb_charger_cur_limit *cur_limit_set)
+{
+	if (!uchger || !cur_limit_set)
+		return -EINVAL;
+
+	uchger->cur_limit.sdp_cur_limit = cur_limit_set->sdp_cur_limit;
+	uchger->cur_limit.dcp_cur_limit = cur_limit_set->dcp_cur_limit;
+	uchger->cur_limit.cdp_cur_limit = cur_limit_set->cdp_cur_limit;
+	uchger->cur_limit.aca_cur_limit = cur_limit_set->aca_cur_limit;
+	return 0;
+}
+
+/*
+ * usb_charger_get_cur_limit() - Get the current limitation by different usb
+ * 		charger type.
+ * @uchger - the usb charger device.
+ * @type - the usb charger type.
+ *
+ * return the current limitation to set.
+ */
+static unsigned int
+usb_charger_get_cur_limit(struct usb_charger *uchger)
+{
+	enum usb_charger_type uchger_type = uchger->type;
+	unsigned int cur_limit;
+
+	switch (uchger_type) {
+	case SDP_TYPE:
+		cur_limit = uchger->cur_limit.sdp_cur_limit;
+		break;
+	case DCP_TYPE:
+		cur_limit = uchger->cur_limit.dcp_cur_limit;
+		break;
+	case CDP_TYPE:
+		cur_limit = uchger->cur_limit.cdp_cur_limit;
+		break;
+	case ACA_TYPE:
+		cur_limit = uchger->cur_limit.aca_cur_limit;
+		break;
+	default:
+		return 0;
+	}
+
+	return cur_limit;
+}
+
+/*
+ * usb_charger_detect_type() - Get the usb charger type by the callback which is
+ * 		implemented by user.
+ * @uchger - the usb charger device.
+ *
+ * return the usb charger type.
+ */
+enum usb_charger_type
+usb_charger_detect_type(struct usb_charger *uchger)
+{
+	if (uchger->gadget && uchger->gadget->ops
+	    && uchger->gadget->ops->get_charger_type)
+		uchger->type =
+			uchger->gadget->ops->get_charger_type(uchger->gadget);
+	else
+		uchger->type = UNKNOWN_TYPE;
+
+	return uchger->type;
+}
+
+/*
+ * usb_charger_notifier_others() - It will notify other device registered on
+ * 		usb charger.
+ * @uchger - the usb charger device.
+ *
+ */
+static void
+usb_charger_notify_others(struct usb_charger *uchger,
+			  enum usb_charger_state state)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&uchger->lock, flags);
+	uchger->state = state;
+
+	switch (state) {
+	case USB_CHARGER_PRESENT:
+		usb_charger_detect_type(uchger);
+		raw_notifier_call_chain(&uchger->uchger_nh,
+			usb_charger_get_cur_limit(uchger),
+			uchger);
+		break;
+	case USB_CHARGER_REMOVE:
+		uchger->type = UNKNOWN_TYPE;
+		raw_notifier_call_chain(&uchger->uchger_nh, 0, uchger);
+		break;
+	default:
+		dev_warn(&uchger->dev, "Unknown USB charger state: %d\n",
+			 state);
+		break;
+	}
+	spin_unlock_irqrestore(&uchger->lock, flags);
+}
+
+/*
+ * usb_charger_plug_by_extcon() - The notifier call function which is registered
+ * 		on the extcon device.
+ * @nb - thr notifier block that notified by extcon device.
+ * @state - the extcon device state changed.
+ * @data - here specify a extcon device.
+ *
+ * return the notify flag.
+ */
+static int
+usb_charger_plug_by_extcon(struct notifier_block *nb,
+			   unsigned long state, void *data)
+{
+	struct usb_charger_nb *extcon_nb =
+		container_of(nb, struct usb_charger_nb, nb);
+	struct usb_charger *uchger = extcon_nb->uchger;
+	enum usb_charger_state uchger_state;
+
+	if (!uchger)
+		return NOTIFY_BAD;
+
+	/* Report event to power to setting the current limitation
+	 * for this usb charger when one usb charger is added or removed
+	 * with detecting by extcon device.
+	 */
+	if (state)
+		uchger_state = USB_CHARGER_PRESENT;
+	else
+		uchger_state = USB_CHARGER_REMOVE;
+
+	usb_charger_notify_others(uchger, uchger_state);
+
+	return NOTIFY_OK;
+}
+
+/*
+ * usb_charger_plug_by_gadget() - Set the usb charger current limitation
+ * 		according to the usb gadget device state.
+ * @data - here specify a usb charger device.
+ *
+ */
+static int
+usb_charger_plug_by_gadget(struct notifier_block *nb,
+			   unsigned long state, void *data)
+{
+	struct usb_gadget *gadget = (struct usb_gadget *)data;
+	struct usb_charger *uchger = gadget->uchger;
+	enum usb_charger_state uchger_state;
+
+	if (!uchger)
+		return NOTIFY_BAD;
+
+	/* Report event to power to setting the current limitation
+	 * for this usb charger when one usb charger state is changed
+	 * with detecting by usb gadget state.
+	 */
+	if (uchger->old_gadget_state != state) {
+		uchger->old_gadget_state = state;
+
+		if (state >= USB_STATE_ATTACHED)
+			uchger_state = USB_CHARGER_PRESENT;
+		else if (state == USB_STATE_NOTATTACHED)
+			uchger_state = USB_CHARGER_REMOVE;
+		else
+			uchger_state = USB_CHARGER_DEFAULT;
+
+		usb_charger_notify_others(uchger, uchger_state);
+	}
+
+	return NOTIFY_OK;
+}
+
+static int devm_uchger_dev_match(struct device *dev, void *res, void *data)
+{
+	struct usb_charger **r = res;
+
+	if (WARN_ON(!r || !*r))
+		return 0;
+
+	return *r == data;
+}
+
+static void usb_charger_release(struct device *dev)
+{
+	struct usb_charger *uchger = dev_get_drvdata(dev);
+
+	if (!atomic_dec_and_test(&uchger->count)) {
+		dev_err(dev, "The usb charger is still in use\n");
+		return;
+	}
+
+	kfree(uchger->name);
+	kfree(uchger);
+}
+
+/*
+ * usb_charger_unregister() - Unregister a usb charger device.
+ * @uchger - the usb charger device.
+ *
+ */
+int usb_charger_unregister(struct usb_charger *uchger)
+{
+	if (!uchger)
+		return -EINVAL;
+
+	mutex_lock(&usb_charger_list_lock);
+	list_del(&uchger->entry);
+	mutex_unlock(&usb_charger_list_lock);
+
+	device_unregister(&uchger->dev);
+	return 0;
+}
+
+static void devm_uchger_dev_unreg(struct device *dev, void *res)
+{
+	usb_charger_unregister(*(struct usb_charger **)res);
+}
+
+void devm_usb_charger_unregister(struct device *dev,
+				 struct usb_charger *uchger)
+{
+	devres_release(dev, devm_uchger_dev_unreg,
+		       devm_uchger_dev_match, uchger);
+}
+
+/*
+ * usb_charger_register() - Register a new usb charger device.
+ * @uchger - the new usb charger device.
+ *
+ */
+int usb_charger_register(struct device *dev, struct usb_charger *uchger)
+{
+	static atomic_t uchger_no = ATOMIC_INIT(-1);
+	struct usb_charger *tmp;
+	int ret;
+
+	if (!uchger) {
+		dev_err(dev, "no device provided for charger\n");
+		return -EINVAL;
+	}
+
+	uchger->dev.parent = dev;
+	uchger->dev.release = usb_charger_release;
+	dev_set_name(&uchger->dev, "usb-chger%lu",
+		     (unsigned long)atomic_inc_return(&uchger_no));
+
+	ret = device_register(&uchger->dev);
+	if (ret) {
+		put_device(&uchger->dev);
+		return ret;
+	}
+
+	dev_set_drvdata(&uchger->dev, uchger);
+
+	mutex_lock(&usb_charger_list_lock);
+	list_for_each_entry(tmp, &usb_charger_list, entry) {
+		if (!(strcmp(tmp->name, uchger->name))) {
+			mutex_unlock(&usb_charger_list_lock);
+			ret = -EEXIST;
+			goto out;
+		}
+	}
+	list_add_tail(&uchger->entry, &usb_charger_list);
+	mutex_unlock(&usb_charger_list_lock);
+
+	return 0;
+
+out:
+	dev_err(dev, "Failed to register usb charger (%s)\n",
+		uchger->name);
+	device_unregister(&uchger->dev);
+	put_device(&uchger->dev);
+	return ret;
+}
+
+int devm_usb_charger_register(struct device *dev,
+			      struct usb_charger *uchger)
+{
+	struct usb_charger **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_uchger_dev_unreg, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = usb_charger_register(dev, uchger);
+	if (ret) {
+		devres_free(ptr);
+		return ret;
+	}
+
+	*ptr = uchger;
+	devres_add(dev, ptr);
+
+	return 0;
+}
+
+int usb_charger_init(struct usb_gadget *ugadget)
+{
+	struct usb_charger *uchger;
+	struct extcon_dev *edev;
+	char buf[100];
+	char *str;
+	int ret;
+
+	if (!ugadget)
+		return -EINVAL;
+
+	uchger = devm_kzalloc(&ugadget->dev, sizeof(struct usb_charger),
+			      GFP_KERNEL);
+	if (!uchger)
+		return -ENOMEM;
+
+	sprintf(buf, "usb-charger.%s", ugadget->name);
+	str = devm_kzalloc(&ugadget->dev, sizeof(char) * (strlen(buf) + 1),
+			   GFP_KERNEL);
+	if (!str)
+		return -ENOMEM;
+
+	strcpy(str, buf);
+	uchger->name = str;
+	uchger->type = UNKNOWN_TYPE;
+	uchger->state = USB_CHARGER_DEFAULT;
+	uchger->cur_limit.sdp_cur_limit = DEFAULT_SDP_CUR_LIMIT;
+	uchger->cur_limit.dcp_cur_limit = DEFAULT_DCP_CUR_LIMIT;
+	uchger->cur_limit.cdp_cur_limit = DEFAULT_CDP_CUR_LIMIT;
+	uchger->cur_limit.aca_cur_limit = DEFAULT_ACA_CUR_LIMIT;
+
+	atomic_set(&uchger->count, 1);
+	spin_lock_init(&uchger->lock);
+	INIT_LIST_HEAD(&uchger->entry);
+	RAW_INIT_NOTIFIER_HEAD(&uchger->uchger_nh);
+
+	/* register a notifier on a extcon device if it is exsited */
+	edev = extcon_get_edev_by_phandle(ugadget->dev.parent, 0);
+	if (!IS_ERR_OR_NULL(edev)) {
+		uchger->extcon_dev = edev;
+		uchger->extcon_nb.nb.notifier_call = usb_charger_plug_by_extcon;
+		uchger->extcon_nb.uchger = uchger;
+		usb_charger_register_extcon_notifier(uchger, edev, EXTCON_USB);
+	}
+
+	/* register a notifier on a usb gadget device */
+	uchger->gadget = ugadget;
+	ugadget->uchger = uchger;
+	uchger->old_gadget_state = ugadget->state;
+	uchger->gadget_nb.notifier_call = usb_charger_plug_by_gadget;
+	usb_charger_register_gadget_notifier(uchger);
+
+	ret = usb_charger_register(&ugadget->dev, uchger);
+	if (ret)
+		goto reg_fail;
+
+	return 0;
+
+reg_fail:
+	if (uchger->extcon_dev)
+		usb_charger_unregister_extcon_notifier(uchger,
+				uchger->extcon_dev, EXTCON_USB);
+
+	usb_charger_unregister_gadget_notifier(uchger);
+	return ret;
+}
+
+int usb_charger_exit(struct usb_gadget *ugadget)
+{
+	struct usb_charger *uchger = ugadget->uchger;
+
+	if (!uchger)
+		return -EINVAL;
+
+	if (uchger->extcon_dev)
+		usb_charger_unregister_extcon_notifier(uchger,
+				uchger->extcon_dev, EXTCON_USB);
+
+	usb_charger_unregister_gadget_notifier(uchger);
+	return usb_charger_unregister(uchger);
+}
+
+MODULE_AUTHOR("Baolin Wang <baolin.wang@xxxxxxxxxx>");
+MODULE_DESCRIPTION("USB charger driver");
diff --git a/include/linux/usb/usb_charger.h b/include/linux/usb/usb_charger.h
new file mode 100644
index 0000000..da4d3c9
--- /dev/null
+++ b/include/linux/usb/usb_charger.h
@@ -0,0 +1,101 @@
+#ifndef __LINUX_USB_CHARGER_H__
+#define __LINUX_USB_CHARGER_H__
+
+#include <linux/device.h>
+#include <linux/notifier.h>
+#include <linux/sysfs.h>
+#include <linux/usb/ch9.h>
+
+/* USB charger type:
+ * SDP (Standard Downstream Port)
+ * DCP (Dedicated Charging Port)
+ * CDP (Charging Downstream Port)
+ * ACA (Accessory Charger Adapters)
+ */
+enum usb_charger_type {
+	UNKNOWN_TYPE,
+	SDP_TYPE,
+	DCP_TYPE,
+	CDP_TYPE,
+	ACA_TYPE,
+};
+
+/* USB charger state */
+enum usb_charger_state {
+	USB_CHARGER_DEFAULT,
+	USB_CHARGER_PRESENT,
+	USB_CHARGER_REMOVE,
+};
+
+/* Current limitation by charger type */
+struct usb_charger_cur_limit {
+	unsigned int sdp_cur_limit;
+	unsigned int dcp_cur_limit;
+	unsigned int cdp_cur_limit;
+	unsigned int aca_cur_limit;
+};
+
+struct usb_charger_nb {
+	struct notifier_block	nb;
+	struct usb_charger	*uchger;
+};
+
+struct usb_charger {
+	/* Internal data. Please do not set. */
+	const char		*name;
+	struct device		dev;
+	struct raw_notifier_head	uchger_nh;
+	struct list_head	entry;
+	spinlock_t		lock;
+	enum usb_charger_type	type;
+	enum usb_charger_state	state;
+	atomic_t		count;
+
+	/* For supporting extcon usb gpio */
+	struct extcon_dev	*extcon_dev;
+	struct usb_charger_nb	extcon_nb;
+
+	/* For supporting usb gadget */
+	struct usb_gadget	*gadget;
+	enum usb_device_state	old_gadget_state;
+	struct notifier_block	gadget_nb;
+
+	/* Current limitation */
+	struct usb_charger_cur_limit	cur_limit;
+};
+
+extern struct usb_charger *usb_charger_find_by_name(char *name);
+
+extern void usb_charger_register_notify(struct usb_charger *uchger,
+					struct notifier_block *nb);
+extern void usb_charger_unregister_notify(struct usb_charger *uchger,
+					  struct notifier_block *nb);
+
+extern int usb_charger_register_extcon_notifier(struct usb_charger *uchger,
+						struct extcon_dev *edev,
+						unsigned int extcon_id);
+extern int usb_charger_unregister_extcon_notifier(struct usb_charger *uchger,
+						  struct extcon_dev *edev,
+						  unsigned int extcon_id);
+
+extern int usb_charger_register_gadget_notifier(struct usb_charger *uchger);
+extern int usb_charger_unregister_gadget_notifier(struct usb_charger *uchger);
+
+extern int usb_charger_set_cur_limit(struct usb_charger *uchger,
+			      struct usb_charger_cur_limit *cur_limit_set);
+extern enum usb_charger_type usb_charger_detect_type(struct usb_charger *uchger);
+
+extern int usb_charger_init(struct usb_gadget *ugadget);
+extern int usb_charger_exit(struct usb_gadget *ugadget);
+
+static inline void get_usb_charger(struct usb_charger *uchger)
+{
+	atomic_inc(&uchger->count);
+}
+
+static inline void put_usb_charger(struct usb_charger *uchger)
+{
+	atomic_dec(&uchger->count);
+}
+
+#endif /* __LINUX_USB_CHARGER_H__ */
-- 
1.7.9.5

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