Re: [PATCH v17 1/4] usb: gadget: Introduce the usb charger framework

[Lu Baolu]

Hi Baolin,

Some review comments below.

On 10/10/2016 02:22 PM, Baolin Wang wrote:
> 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 |  785 ++++++++++++++++++++++++++++++++++++++
>  include/linux/usb/charger.h      |  186 +++++++++
>  include/uapi/linux/usb/charger.h |   31 ++
>  5 files changed, 1011 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..16dc477
> --- /dev/null
> +++ b/drivers/usb/gadget/udc/charger.c
> @@ -0,0 +1,785 @@
> +/*
> + * 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;
> +}

Are there any duplicated code in this function and __usb_charger_get_type()?

> +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.
> + */

Where is usb_charger_unregister()?

> +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);
> +		goto fail;
> +	}
> +
> +	mutex_lock(&charger_lock);
> +	list_add_tail(&uchger->list, &charger_list);
> +	mutex_unlock(&charger_lock);
> +
> +	return 0;
> +
> +fail:
> +	ida_simple_remove(&usb_charger_ida, uchger->id);
> +	uchger->id = -1;
> +	return ret;

You only have one point to goto here. Why not just move this code block
to above goto place?

> +}
> +
> +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);

Memory leak. I didn't find kfree() in usb_charger_exit().
 
> +	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..7819eac
> --- /dev/null
> +++ b/include/linux/usb/charger.h
> @@ -0,0 +1,186 @@
> +#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;

Needs comments for 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
> +extern struct usb_charger *usb_charger_find_by_name(const char *name);
> +
> +extern int usb_charger_register_notify(struct usb_charger *uchger,
> +				       struct notifier_block *nb);
> +extern int usb_charger_unregister_notify(struct usb_charger *uchger,
> +					 struct notifier_block *nb);
> +
> +extern int usb_charger_set_current(struct usb_charger *uchger,
> +				   struct usb_charger_current *values);
> +extern int usb_charger_get_current(struct usb_charger *uchger,
> +				   unsigned int *min, unsigned int *max);
> +
> +extern int usb_charger_set_cur_limit_by_type(struct usb_charger *uchger,
> +					     enum usb_charger_type type,
> +					     unsigned int cur_limit);
> +extern int usb_charger_set_cur_limit_by_gadget(struct usb_gadget *gadget,
> +					       unsigned int cur_limit);
> +
> +extern int usb_charger_plug_by_gadget(struct usb_gadget *gadget,
> +				      unsigned long state);
> +extern enum usb_charger_type usb_charger_get_type(struct usb_charger *uchger);
> +extern int usb_charger_detect_type(struct usb_charger *uchger);
> +extern enum usb_charger_state usb_charger_get_state(struct usb_charger *uchger);
> +
> +extern int usb_charger_init(struct usb_gadget *ugadget);
> +extern int usb_charger_exit(struct usb_gadget *ugadget);

You don't need to put "extern" here.

Please use "scripts/checkpatch.pl --strict" to check this.

> +#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 */

Best regards,
Lu Baolu