[PATCH v18 1/4] usb: 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. It also supplies the
notification mechanism to userspace When the usb charger state is changed.

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.

This patch doesn't yet integrate with the gadget code, so some functions
which rely on the 'gadget' are not completed, that will be implemented
in the following patches.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
Reviewed-by: Li Jun <jun.li@xxxxxxx>
Tested-by: Li Jun <jun.li@xxxxxxx>
---
 drivers/usb/gadget/Kconfig       |    8 +
 drivers/usb/gadget/udc/Makefile  |    1 +
 drivers/usb/gadget/udc/charger.c |  782 ++++++++++++++++++++++++++++++++++++++
 include/linux/usb/charger.h      |  185 +++++++++
 include/uapi/linux/usb/charger.h |   31 ++
 5 files changed, 1007 insertions(+)
 create mode 100644 drivers/usb/gadget/udc/charger.c
 create mode 100644 include/linux/usb/charger.h
 create mode 100644 include/uapi/linux/usb/charger.h

diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 2ea3fc3..7520677 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -134,6 +134,14 @@ config U_SERIAL_CONSOLE
 	help
 	   It supports the serial gadget can be used as a console.
 
+config USB_CHARGER
+	bool "USB charger support"
+	select EXTCON
+	help
+	  The usb charger driver based on the usb gadget that makes an
+	  enhancement to a power driver which can set the current limitation
+	  when the usb charger is added or removed.
+
 source "drivers/usb/gadget/udc/Kconfig"
 
 #
diff --git a/drivers/usb/gadget/udc/Makefile b/drivers/usb/gadget/udc/Makefile
index 98e74ed..ede2351 100644
--- a/drivers/usb/gadget/udc/Makefile
+++ b/drivers/usb/gadget/udc/Makefile
@@ -2,6 +2,7 @@
 CFLAGS_trace.o			:= -I$(src)
 
 udc-core-y			:= core.o trace.o
+udc-core-$(CONFIG_USB_CHARGER)	+= charger.o
 
 #
 # USB peripheral controller drivers
diff --git a/drivers/usb/gadget/udc/charger.c b/drivers/usb/gadget/udc/charger.c
new file mode 100644
index 0000000..d885e86
--- /dev/null
+++ b/drivers/usb/gadget/udc/charger.c
@@ -0,0 +1,782 @@
+/*
+ * charger.c -- USB charger driver
+ *
+ * Copyright (C) 2016 Linaro Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#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/slab.h>
+#include <linux/usb.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/charger.h>
+
+/* Default current range by charger type. */
+#define DEFAULT_SDP_CUR_MIN	2
+#define DEFAULT_SDP_CUR_MAX	500
+#define DEFAULT_SDP_CUR_MIN_SS	150
+#define DEFAULT_SDP_CUR_MAX_SS	900
+#define DEFAULT_DCP_CUR_MIN	500
+#define DEFAULT_DCP_CUR_MAX	5000
+#define DEFAULT_CDP_CUR_MIN	1500
+#define DEFAULT_CDP_CUR_MAX	5000
+#define DEFAULT_ACA_CUR_MIN	1500
+#define DEFAULT_ACA_CUR_MAX	5000
+
+static DEFINE_IDA(usb_charger_ida);
+static LIST_HEAD(charger_list);
+static DEFINE_MUTEX(charger_lock);
+
+static struct usb_charger *dev_to_uchger(struct device *dev)
+{
+	return NULL;
+}
+
+/*
+ * charger_current_show() - Show the charger current.
+ */
+static ssize_t charger_current_show(struct device *dev,
+				    struct device_attribute *attr,
+				    char *buf)
+{
+	struct usb_charger *uchger = dev_to_uchger(dev);
+	unsigned int min, max;
+
+	usb_charger_get_current(uchger, &min, &max);
+	return sprintf(buf, "%u-%u\n", min, max);
+}
+static DEVICE_ATTR_RO(charger_current);
+
+/*
+ * charger_type_show() - Show the charger type.
+ *
+ * It can be SDP/DCP/CDP/ACA type, else for unknown type.
+ */
+static ssize_t charger_type_show(struct device *dev,
+				 struct device_attribute *attr,
+				 char *buf)
+{
+	struct usb_charger *uchger = dev_to_uchger(dev);
+	int cnt;
+
+	switch (uchger->type) {
+	case SDP_TYPE:
+		cnt = sprintf(buf, "%s\n", "SDP");
+		break;
+	case DCP_TYPE:
+		cnt = sprintf(buf, "%s\n", "DCP");
+		break;
+	case CDP_TYPE:
+		cnt = sprintf(buf, "%s\n", "CDP");
+		break;
+	case ACA_TYPE:
+		cnt = sprintf(buf, "%s\n", "ACA");
+		break;
+	default:
+		cnt = sprintf(buf, "%s\n", "UNKNOWN");
+		break;
+	}
+
+	return cnt;
+}
+static DEVICE_ATTR_RO(charger_type);
+
+/*
+ * charger_state_show() - Show the charger state.
+ *
+ * Charger state can be present or removed.
+ */
+static ssize_t charger_state_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct usb_charger *uchger = dev_to_uchger(dev);
+	int cnt;
+
+	switch (uchger->state) {
+	case USB_CHARGER_PRESENT:
+		cnt = sprintf(buf, "%s\n", "PRESENT");
+		break;
+	case USB_CHARGER_REMOVE:
+		cnt = sprintf(buf, "%s\n", "REMOVE");
+		break;
+	default:
+		cnt = sprintf(buf, "%s\n", "UNKNOWN");
+		break;
+	}
+
+	return cnt;
+}
+static DEVICE_ATTR_RO(charger_state);
+
+static struct attribute *usb_charger_attrs[] = {
+	&dev_attr_charger_current.attr,
+	&dev_attr_charger_type.attr,
+	&dev_attr_charger_state.attr,
+	NULL
+};
+
+static const struct attribute_group usb_charger_group = {
+	.name = "charger",
+	.attrs = usb_charger_attrs,
+};
+__ATTRIBUTE_GROUPS(usb_charger);
+
+/*
+ * usb_charger_find_by_name() - Get the usb charger instance by name.
+ * @name - usb charger name.
+ */
+struct usb_charger *usb_charger_find_by_name(const char *name)
+{
+	struct usb_charger *uchger;
+
+	if (WARN(!name, "can't work with NULL name"))
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&charger_lock);
+	list_for_each_entry(uchger, &charger_list, list) {
+		if (!strcmp(uchger->name, name))
+			break;
+	}
+	mutex_unlock(&charger_lock);
+
+	if (WARN(!uchger, "can't find usb charger"))
+		return ERR_PTR(-ENODEV);
+
+	return uchger;
+}
+EXPORT_SYMBOL_GPL(usb_charger_find_by_name);
+
+/*
+ * __usb_charger_get_type() - Get the usb charger type by the callback which
+ * is implemented by users.
+ * @uchger - the usb charger instance.
+ *
+ * Note: This function is just used for getting the charger type, not for
+ * detecting charger type which might affect the DP/DM line when gadget is on
+ * enumeration state.
+ */
+static enum usb_charger_type __usb_charger_get_type(struct usb_charger *uchger)
+{
+	if (uchger->type != UNKNOWN_TYPE)
+		return uchger->type;
+
+	if (uchger->get_charger_type)
+		uchger->type = uchger->get_charger_type(uchger);
+	else
+		uchger->type = UNKNOWN_TYPE;
+
+	return uchger->type;
+}
+
+/*
+ * usb_charger_get_type() - get the usb charger type with lock protection.
+ * @uchger - usb charger instance.
+ *
+ * Users can get the charger type by this safe API, rather than using the
+ * usb_charger structure directly.
+ */
+enum usb_charger_type usb_charger_get_type(struct usb_charger *uchger)
+{
+	enum usb_charger_type type;
+
+	mutex_lock(&uchger->lock);
+	type = __usb_charger_get_type(uchger);
+	mutex_unlock(&uchger->lock);
+
+	return type;
+}
+EXPORT_SYMBOL_GPL(usb_charger_get_type);
+
+/*
+ * usb_charger_get_state() - Get the charger state with lock protection.
+ * @uchger - the usb charger instance.
+ *
+ * Users should get the charger state by this safe API.
+ */
+enum usb_charger_state usb_charger_get_state(struct usb_charger *uchger)
+{
+	enum usb_charger_state state;
+
+	mutex_lock(&uchger->lock);
+	state = uchger->state;
+	mutex_unlock(&uchger->lock);
+
+	return state;
+}
+EXPORT_SYMBOL_GPL(usb_charger_get_state);
+
+/*
+ * usb_charger_detect_type() - detect the charger type manually.
+ * @uchger - usb charger instance.
+ *
+ * Note: You should ensure you need to detect the charger type manually on your
+ * platform.
+ * You should call it at the right gadget state to avoid affecting gadget
+ * enumeration.
+ */
+int usb_charger_detect_type(struct usb_charger *uchger)
+{
+	enum usb_charger_type type;
+
+	if (!uchger->charger_detect)
+		return -EINVAL;
+
+	type = uchger->charger_detect(uchger);
+
+	mutex_lock(&uchger->lock);
+	uchger->type = type;
+	mutex_unlock(&uchger->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_charger_detect_type);
+
+/*
+ * usb_charger_notify_work() - Notify users the current has changed by work.
+ * @work - the work instance.
+ *
+ * Note: When users receive the charger present event, they should check the
+ * charger current by usb_charger_get_current() API.
+ */
+static void usb_charger_notify_work(struct work_struct *work)
+{
+	struct usb_charger *uchger = work_to_charger(work);
+
+	mutex_lock(&uchger->lock);
+	if (uchger->state == USB_CHARGER_PRESENT) {
+		raw_notifier_call_chain(&uchger->uchger_nh,
+					USB_CHARGER_PRESENT,
+					uchger);
+	}
+	mutex_unlock(&uchger->lock);
+}
+
+/*
+ * __usb_charger_set_cur_limit_by_type() - Set the current limitation
+ * by charger type.
+ * @uchger - the usb charger instance.
+ * @type - the usb charger type.
+ * @cur_limit - the current limitation.
+ */
+static int __usb_charger_set_cur_limit_by_type(struct usb_charger *uchger,
+					       enum usb_charger_type type,
+					       unsigned int cur_limit)
+{
+	switch (type) {
+	case SDP_TYPE:
+		uchger->cur.sdp_max = (cur_limit > DEFAULT_SDP_CUR_MAX) ?
+			DEFAULT_SDP_CUR_MAX : cur_limit;
+		uchger->sdp_default_cur_change = 1;
+		break;
+	case DCP_TYPE:
+		uchger->cur.dcp_max = (cur_limit > DEFAULT_DCP_CUR_MAX) ?
+			DEFAULT_DCP_CUR_MAX : cur_limit;
+		break;
+	case CDP_TYPE:
+		uchger->cur.cdp_max = (cur_limit > DEFAULT_CDP_CUR_MAX) ?
+			DEFAULT_CDP_CUR_MAX : cur_limit;
+		break;
+	case ACA_TYPE:
+		uchger->cur.aca_max = (cur_limit > DEFAULT_ACA_CUR_MAX) ?
+			DEFAULT_ACA_CUR_MAX : cur_limit;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * usb_charger_set_cur_limit_by_gadget() - Set the current limitation from
+ * gadget layer.
+ * @gadget - the usb gadget device.
+ * @cur_limit - the current limitation.
+ *
+ * Note: This function is used in atomic contexts without mutex lock.
+ */
+int usb_charger_set_cur_limit_by_gadget(struct usb_gadget *gadget,
+					unsigned int cur_limit)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_charger_set_cur_limit_by_gadget);
+
+/*
+ * usb_charger_set_cur_limit_by_type() - Set the current limitation
+ * by charger type with lock protection.
+ * @uchger - the usb charger instance.
+ * @type - the usb charger type.
+ * @cur_limit - the current limitation.
+ *
+ * Users should set the current limitation by this lock protection API.
+ */
+int usb_charger_set_cur_limit_by_type(struct usb_charger *uchger,
+				      enum usb_charger_type type,
+				      unsigned int cur_limit)
+{
+	int ret;
+
+	if (!uchger)
+		return -EINVAL;
+
+	mutex_lock(&uchger->lock);
+	ret = __usb_charger_set_cur_limit_by_type(uchger, type, cur_limit);
+	mutex_unlock(&uchger->lock);
+
+	schedule_work(&uchger->work);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_charger_set_cur_limit_by_type);
+
+/*
+ * usb_charger_set_current() - Set the usb charger current.
+ * @uchger - the usb charger instance.
+ * @values - the current setting values.
+ */
+int usb_charger_set_current(struct usb_charger *uchger,
+			    struct usb_charger_current *values)
+{
+	if (!uchger || !values)
+		return -EINVAL;
+
+	mutex_lock(&uchger->lock);
+	uchger->cur.sdp_min = values->sdp_min;
+	uchger->cur.sdp_max = (values->sdp_max > DEFAULT_SDP_CUR_MAX) ?
+		DEFAULT_SDP_CUR_MAX : values->sdp_max;
+	uchger->cur.dcp_min = values->dcp_min;
+	uchger->cur.dcp_max = (values->dcp_max > DEFAULT_DCP_CUR_MAX) ?
+		DEFAULT_DCP_CUR_MAX : values->dcp_max;
+	uchger->cur.cdp_min = values->cdp_min;
+	uchger->cur.cdp_max = (values->cdp_max > DEFAULT_CDP_CUR_MAX) ?
+		DEFAULT_CDP_CUR_MAX : values->cdp_max;
+	uchger->cur.aca_min = values->aca_min;
+	uchger->cur.aca_max = (values->aca_max > DEFAULT_ACA_CUR_MAX) ?
+		DEFAULT_ACA_CUR_MAX : values->aca_max;
+	uchger->sdp_default_cur_change = 2;
+	mutex_unlock(&uchger->lock);
+
+	schedule_work(&uchger->work);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_charger_set_current);
+
+/*
+ * usb_charger_get_current() - Get the charger current with lock protection.
+ * @uchger - the usb charger instance.
+ * @min - return the minimum current.
+ * @max - return the maximum current.
+ *
+ * Users should get the charger current by this safe API.
+ */
+int usb_charger_get_current(struct usb_charger *uchger,
+			    unsigned int *min,
+			    unsigned int *max)
+{
+	enum usb_charger_type type;
+
+	if (!uchger)
+		return -EINVAL;
+
+	mutex_lock(&uchger->lock);
+	type = __usb_charger_get_type(uchger);
+
+	switch (type) {
+	case SDP_TYPE:
+		/*
+		 * For super speed gadget, the default charger maximum current
+		 * should be 900 mA and the default minimum current should be
+		 * 150mA.
+		 */
+		if (uchger->sdp_default_cur_change != 2 && uchger->gadget &&
+		    uchger->gadget->speed >= USB_SPEED_SUPER) {
+			if (!uchger->sdp_default_cur_change)
+				uchger->cur.sdp_max = DEFAULT_SDP_CUR_MAX_SS;
+			uchger->cur.sdp_min = DEFAULT_SDP_CUR_MIN_SS;
+			uchger->sdp_default_cur_change = 2;
+		}
+
+		*min = uchger->cur.sdp_min;
+		*max = uchger->cur.sdp_max;
+		break;
+	case DCP_TYPE:
+		*min = uchger->cur.dcp_min;
+		*max = uchger->cur.dcp_max;
+		break;
+	case CDP_TYPE:
+		*min = uchger->cur.cdp_min;
+		*max = uchger->cur.cdp_max;
+		break;
+	case ACA_TYPE:
+		*min = uchger->cur.aca_min;
+		*max = uchger->cur.aca_max;
+		break;
+	default:
+		*min = 0;
+		*max = 0;
+		break;
+	}
+	mutex_unlock(&uchger->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_charger_get_current);
+
+/*
+ * usb_charger_register_notify() - Register a notifiee to get notified by
+ * any attach status changes from the usb charger detection.
+ * @uchger - the usb charger instance which is monitored.
+ * @nb - a notifier block to be registered.
+ */
+int usb_charger_register_notify(struct usb_charger *uchger,
+				struct notifier_block *nb)
+{
+	int ret;
+
+	if (!uchger || !nb) {
+		pr_err("Charger or nb can not be NULL.\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&uchger->lock);
+	ret = raw_notifier_chain_register(&uchger->uchger_nh, nb);
+	mutex_unlock(&uchger->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_charger_register_notify);
+
+/*
+ * usb_charger_unregister_notify() - Unregister a notifiee from the usb charger.
+ * @uchger - the usb charger instance which is monitored.
+ * @nb - a notifier block to be unregistered.
+ */
+int usb_charger_unregister_notify(struct usb_charger *uchger,
+				  struct notifier_block *nb)
+{
+	int ret;
+
+	if (!uchger || !nb) {
+		pr_err("Charger or nb can not be NULL.\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&uchger->lock);
+	ret = raw_notifier_chain_unregister(&uchger->uchger_nh, nb);
+	mutex_unlock(&uchger->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(usb_charger_unregister_notify);
+
+/*
+ * usb_charger_notify_state() - It will notify other device registered
+ * on usb charger when the usb charger state is changed.
+ * @uchger - the usb charger instance.
+ * @state - the state of the usb charger.
+ *
+ * Note: When notify the charger present state to power driver, the power driver
+ * should get the current by usb_charger_get_current() API to set current.
+ */
+static void usb_charger_notify_state(struct usb_charger *uchger,
+				     enum usb_charger_state state)
+{
+	char uchger_state[50] = { 0 };
+	char *envp[] = { uchger_state, NULL };
+
+	mutex_lock(&uchger->lock);
+	if (uchger->state == state) {
+		mutex_unlock(&uchger->lock);
+		return;
+	}
+
+	uchger->state = state;
+
+	switch (state) {
+	case USB_CHARGER_PRESENT:
+		__usb_charger_get_type(uchger);
+		raw_notifier_call_chain(&uchger->uchger_nh,
+					USB_CHARGER_PRESENT,
+					uchger);
+		snprintf(uchger_state, ARRAY_SIZE(uchger_state),
+			 "USB_CHARGER_STATE=%s", "USB_CHARGER_PRESENT");
+		break;
+	case USB_CHARGER_REMOVE:
+		uchger->type = UNKNOWN_TYPE;
+		raw_notifier_call_chain(&uchger->uchger_nh,
+					USB_CHARGER_REMOVE,
+					uchger);
+		snprintf(uchger_state, ARRAY_SIZE(uchger_state),
+			 "USB_CHARGER_STATE=%s", "USB_CHARGER_REMOVE");
+		break;
+	default:
+		pr_warn("Unknown USB charger state: %d\n", state);
+		mutex_unlock(&uchger->lock);
+		return;
+	}
+
+	kobject_uevent_env(&uchger->gadget->dev.kobj, KOBJ_CHANGE, envp);
+	mutex_unlock(&uchger->lock);
+}
+
+/*
+ * usb_charger_type_by_extcon() - The notifier call function which is registered
+ * on the extcon device.
+ * @nb - the notifier block that notified by extcon device.
+ * @state - the extcon device state.
+ * @data - here specify a extcon device.
+ *
+ * return the notify flag.
+ */
+static int usb_charger_type_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;
+	enum usb_charger_type type;
+
+	if (WARN(!uchger, "charger can not be NULL"))
+		return NOTIFY_BAD;
+
+	/* Determine charger type */
+	if (extcon_get_cable_state_(uchger->extcon_dev,
+				    EXTCON_CHG_USB_SDP) > 0) {
+		type = SDP_TYPE;
+		uchger_state = USB_CHARGER_PRESENT;
+	} else if (extcon_get_cable_state_(uchger->extcon_dev,
+					   EXTCON_CHG_USB_CDP) > 0) {
+		type = CDP_TYPE;
+		uchger_state = USB_CHARGER_PRESENT;
+	} else if (extcon_get_cable_state_(uchger->extcon_dev,
+					   EXTCON_CHG_USB_DCP) > 0) {
+		type = DCP_TYPE;
+		uchger_state = USB_CHARGER_PRESENT;
+	} else if (extcon_get_cable_state_(uchger->extcon_dev,
+					   EXTCON_CHG_USB_ACA) > 0) {
+		type = ACA_TYPE;
+		uchger_state = USB_CHARGER_PRESENT;
+	} else {
+		type = UNKNOWN_TYPE;
+		uchger_state = USB_CHARGER_REMOVE;
+	}
+
+	mutex_lock(&uchger->lock);
+	uchger->type = type;
+	mutex_unlock(&uchger->lock);
+
+	usb_charger_notify_state(uchger, uchger_state);
+
+	return NOTIFY_OK;
+}
+
+/*
+ * usb_charger_plug_by_extcon() - The notifier call function which is registered
+ * on the extcon device.
+ * @nb - the notifier block that notified by extcon device.
+ * @state - the extcon device state.
+ * @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 (WARN(!uchger, "charger can not be NULL"))
+		return NOTIFY_BAD;
+
+	/*
+	 * Report event to power users 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_state(uchger, uchger_state);
+
+	return NOTIFY_OK;
+}
+
+/*
+ * usb_charger_plug_by_gadget() - Set the usb charger current limitation
+ * according to the usb gadget device state.
+ * @gadget - the usb gadget device.
+ * @state - the usb gadget state.
+ */
+int usb_charger_plug_by_gadget(struct usb_gadget *gadget,
+			       unsigned long state)
+{
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_charger_plug_by_gadget);
+
+/*
+ * usb_charger_register() - Register a new usb charger.
+ * @uchger - the new usb charger instance.
+ */
+static int usb_charger_register(struct usb_charger *uchger)
+{
+	int ret;
+
+	ret = ida_simple_get(&usb_charger_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0) {
+		pr_err("Failed to register usb charger: %d\n", ret);
+		return ret;
+	}
+
+	uchger->id = ret;
+	scnprintf(uchger->name, CHARGER_NAME_MAX, "usb-charger.%d", uchger->id);
+
+	ret = sysfs_create_groups(&uchger->gadget->dev.kobj,
+				  usb_charger_groups);
+	if (ret) {
+		pr_err("Failed to create usb charger attributes: %d\n", ret);
+		ida_simple_remove(&usb_charger_ida, uchger->id);
+		uchger->id = -1;
+		return ret;
+	}
+
+	mutex_lock(&charger_lock);
+	list_add_tail(&uchger->list, &charger_list);
+	mutex_unlock(&charger_lock);
+
+	return 0;
+}
+
+int usb_charger_init(struct usb_gadget *ugadget)
+{
+	struct usb_charger *uchger;
+	struct extcon_dev *edev;
+	int ret;
+
+	uchger = kzalloc(sizeof(struct usb_charger), GFP_KERNEL);
+	if (!uchger)
+		return -ENOMEM;
+
+	uchger->type = UNKNOWN_TYPE;
+	uchger->state = USB_CHARGER_DEFAULT;
+	uchger->id = -1;
+	uchger->sdp_default_cur_change = 0;
+
+	uchger->cur.sdp_min = DEFAULT_SDP_CUR_MIN;
+	uchger->cur.sdp_max = DEFAULT_SDP_CUR_MAX;
+	uchger->cur.dcp_min = DEFAULT_DCP_CUR_MIN;
+	uchger->cur.dcp_max = DEFAULT_DCP_CUR_MAX;
+	uchger->cur.cdp_min = DEFAULT_CDP_CUR_MIN;
+	uchger->cur.cdp_max = DEFAULT_CDP_CUR_MAX;
+	uchger->cur.aca_min = DEFAULT_ACA_CUR_MIN;
+	uchger->cur.aca_max = DEFAULT_ACA_CUR_MAX;
+
+	mutex_init(&uchger->lock);
+	RAW_INIT_NOTIFIER_HEAD(&uchger->uchger_nh);
+	INIT_WORK(&uchger->work, usb_charger_notify_work);
+
+	/* 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;
+		ret = extcon_register_notifier(edev, EXTCON_USB,
+					       &uchger->extcon_nb.nb);
+		if (ret) {
+			pr_err("Failed to register extcon USB notifier.\n");
+			goto fail_extcon;
+		}
+
+		uchger->extcon_type_nb.nb.notifier_call =
+					usb_charger_type_by_extcon;
+		uchger->extcon_type_nb.uchger = uchger;
+
+		ret = extcon_register_notifier(edev, EXTCON_CHG_USB_SDP,
+					       &uchger->extcon_type_nb.nb);
+		if (ret) {
+			pr_err("Failed to register extcon USB SDP notifier.\n");
+			goto fail_extcon_sdp;
+		}
+
+		ret = extcon_register_notifier(edev, EXTCON_CHG_USB_CDP,
+					       &uchger->extcon_type_nb.nb);
+		if (ret) {
+			pr_err("Failed to register extcon USB CDP notifier.\n");
+			goto fail_extcon_cdp;
+		}
+
+		ret = extcon_register_notifier(edev, EXTCON_CHG_USB_DCP,
+					       &uchger->extcon_type_nb.nb);
+		if (ret) {
+			pr_err("Failed to register extcon USB DCP notifier.\n");
+			goto fail_extcon_dcp;
+		}
+
+		ret = extcon_register_notifier(edev, EXTCON_CHG_USB_ACA,
+					       &uchger->extcon_type_nb.nb);
+		if (ret) {
+			pr_err("Failed to register extcon USB ACA notifier.\n");
+			goto fail_extcon_aca;
+		}
+	}
+
+	uchger->gadget = ugadget;
+	uchger->old_gadget_state = USB_STATE_NOTATTACHED;
+
+	/* Register a new usb charger */
+	ret = usb_charger_register(uchger);
+	if (ret)
+		goto fail_register;
+
+	return 0;
+
+fail_register:
+	extcon_unregister_notifier(uchger->extcon_dev,
+				   EXTCON_CHG_USB_ACA,
+				   &uchger->extcon_type_nb.nb);
+fail_extcon_aca:
+	extcon_unregister_notifier(uchger->extcon_dev,
+				   EXTCON_CHG_USB_DCP,
+				   &uchger->extcon_type_nb.nb);
+fail_extcon_dcp:
+	extcon_unregister_notifier(uchger->extcon_dev,
+				   EXTCON_CHG_USB_CDP,
+				   &uchger->extcon_type_nb.nb);
+fail_extcon_cdp:
+	extcon_unregister_notifier(uchger->extcon_dev,
+				   EXTCON_CHG_USB_SDP,
+				   &uchger->extcon_type_nb.nb);
+fail_extcon_sdp:
+	extcon_unregister_notifier(uchger->extcon_dev,
+				   EXTCON_USB,
+				   &uchger->extcon_nb.nb);
+fail_extcon:
+	kfree(uchger);
+
+	return ret;
+}
+
+int usb_charger_exit(struct usb_gadget *ugadget)
+{
+	return 0;
+}
+
+MODULE_AUTHOR("Baolin Wang <baolin.wang@xxxxxxxxxx>");
+MODULE_DESCRIPTION("USB charger driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/usb/charger.h b/include/linux/usb/charger.h
new file mode 100644
index 0000000..1ca97370
--- /dev/null
+++ b/include/linux/usb/charger.h
@@ -0,0 +1,185 @@
+#ifndef __LINUX_USB_CHARGER_H__
+#define __LINUX_USB_CHARGER_H__
+
+#include <uapi/linux/usb/ch9.h>
+#include <uapi/linux/usb/charger.h>
+
+#define CHARGER_NAME_MAX	30
+#define work_to_charger(w)	(container_of((w), struct usb_charger, work))
+
+/* Current range by charger type */
+struct usb_charger_current {
+	unsigned int sdp_min;
+	unsigned int sdp_max;
+	unsigned int dcp_min;
+	unsigned int dcp_max;
+	unsigned int cdp_min;
+	unsigned int cdp_max;
+	unsigned int aca_min;
+	unsigned int aca_max;
+};
+
+struct usb_charger_nb {
+	struct notifier_block	nb;
+	struct usb_charger	*uchger;
+};
+
+/**
+ * struct usb_charger - describe one usb charger
+ * @name: Charger name.
+ * @list: For linking usb charger instances into one global list.
+ * @uchger_nh: Notifier head for users to register.
+ * @lock: Protect the notifier head and charger.
+ * @id: The charger id.
+ * @type: The charger type, it can be SDP_TYPE, DCP_TYPE, CDP_TYPE or
+ * ACA_TYPE.
+ * @state: Indicate the charger state.
+ * @cur: Describe the current range by charger type.
+ * @work: Workqueue to be used for reporting users current has changed.
+ * @extcon_dev: For supporting extcon usb gpio device to detect usb cable
+ * event (plugin or not).
+ * @extcon_nb: Report the events to charger from extcon device.
+ * @extcon_type_nb: Report the charger type from extcon device.
+ * @gadget: One usb charger is always tied to one usb gadget.
+ * @old_gadget_state: Record the previous state of one usb gadget to check if
+ * the gadget state is changed. If gadget state is changed, then notify the
+ * event to charger.
+ * @sdp_default_cur_change: Check if it is needed to change the SDP charger
+ * default maximum current.
+ * @get_charger_type: User can get charger type by implementing this callback.
+ * @charger_detect: Charger detection method can be implemented if you need to
+ * manually detect the charger type.
+ *
+ * Users can set 'get_charger_type' and 'charger_detect' callbacks directly
+ * according to their own requirements. Beyond that, users can not touch
+ * anything else directly in this structure.
+ */
+struct usb_charger {
+	char				name[CHARGER_NAME_MAX];
+	struct list_head		list;
+	struct raw_notifier_head	uchger_nh;
+	struct mutex			lock;
+	int				id;
+	enum usb_charger_type		type;
+	enum usb_charger_state		state;
+	struct usb_charger_current	cur;
+	struct work_struct		work;
+
+	struct extcon_dev		*extcon_dev;
+	struct usb_charger_nb		extcon_nb;
+	struct usb_charger_nb		extcon_type_nb;
+
+	struct usb_gadget		*gadget;
+	enum usb_device_state		old_gadget_state;
+	unsigned int			sdp_default_cur_change;
+
+	enum usb_charger_type	(*get_charger_type)(struct usb_charger *);
+	enum usb_charger_type	(*charger_detect)(struct usb_charger *);
+};
+
+#ifdef CONFIG_USB_CHARGER
+struct usb_charger *usb_charger_find_by_name(const char *name);
+
+int usb_charger_register_notify(struct usb_charger *uchger,
+				struct notifier_block *nb);
+int usb_charger_unregister_notify(struct usb_charger *uchger,
+				  struct notifier_block *nb);
+
+int usb_charger_set_current(struct usb_charger *uchger,
+			    struct usb_charger_current *values);
+int usb_charger_get_current(struct usb_charger *uchger,
+			    unsigned int *min, unsigned int *max);
+
+int usb_charger_set_cur_limit_by_type(struct usb_charger *uchger,
+				      enum usb_charger_type type,
+				      unsigned int cur_limit);
+int usb_charger_set_cur_limit_by_gadget(struct usb_gadget *gadget,
+					unsigned int cur_limit);
+
+int usb_charger_plug_by_gadget(struct usb_gadget *gadget, unsigned long state);
+enum usb_charger_type usb_charger_get_type(struct usb_charger *uchger);
+int usb_charger_detect_type(struct usb_charger *uchger);
+enum usb_charger_state usb_charger_get_state(struct usb_charger *uchger);
+
+int usb_charger_init(struct usb_gadget *ugadget);
+int usb_charger_exit(struct usb_gadget *ugadget);
+#else
+static inline struct usb_charger *usb_charger_find_by_name(const char *name)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline int usb_charger_register_notify(struct usb_charger *uchger,
+					      struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int usb_charger_unregister_notify(struct usb_charger *uchger,
+						struct notifier_block *nb)
+{
+	return 0;
+}
+
+static inline int usb_charger_set_current(struct usb_charger *uchger,
+					  struct usb_charger_current *values)
+{
+	return 0;
+}
+
+static inline int usb_charger_get_current(struct usb_charger *uchger,
+					  unsigned int *min, unsigned int *max)
+{
+	return 0;
+}
+
+static inline int
+usb_charger_set_cur_limit_by_type(struct usb_charger *uchger,
+				  enum usb_charger_type type,
+				  unsigned int cur_limit)
+{
+	return 0;
+}
+
+static inline int
+usb_charger_set_cur_limit_by_gadget(struct usb_gadget *gadget,
+				    unsigned int cur_limit)
+{
+	return 0;
+}
+
+static inline enum usb_charger_type
+usb_charger_get_type(struct usb_charger *uchger)
+{
+	return UNKNOWN_TYPE;
+}
+
+static inline enum usb_charger_state
+usb_charger_get_state(struct usb_charger *uchger)
+{
+	return USB_CHARGER_REMOVE;
+}
+
+static inline int usb_charger_detect_type(struct usb_charger *uchger)
+{
+	return 0;
+}
+
+static inline int usb_charger_plug_by_gadget(struct usb_gadget *gadget,
+					     unsigned long state)
+{
+	return 0;
+}
+
+static inline int usb_charger_init(struct usb_gadget *ugadget)
+{
+	return 0;
+}
+
+static inline int usb_charger_exit(struct usb_gadget *ugadget)
+{
+	return 0;
+}
+#endif
+
+#endif /* __LINUX_USB_CHARGER_H__ */
diff --git a/include/uapi/linux/usb/charger.h b/include/uapi/linux/usb/charger.h
new file mode 100644
index 0000000..3c56ec4
--- /dev/null
+++ b/include/uapi/linux/usb/charger.h
@@ -0,0 +1,31 @@
+/*
+ * This file defines the USB charger type and state that are needed for
+ * USB device APIs.
+ */
+
+#ifndef _UAPI__LINUX_USB_CHARGER_H
+#define _UAPI__LINUX_USB_CHARGER_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,
+};
+
+#endif /* _UAPI__LINUX_USB_CHARGER_H */
-- 
1.7.9.5