Date:	Fri, 14 Aug 2015 08:27:23 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Baolin Wang <baolin.wang@...aro.org>
Cc:	balbi@...com, broonie@...nel.org, linus.walleij@...aro.org,
	linux-kernel@...r.kernel.org, peter.chen@...escale.com,
	sojka@...ica.cz, stern@...land.harvard.edu, r.baldyga@...sung.com,
	yoshihiro.shimoda.uh@...esas.com, linux-usb@...r.kernel.org,
	device-mainlining@...ts.linuxfoundation.org, sre@...nel.org,
	dbaryshkov@...il.com, dwmw2@...radead.org, sameo@...ux.intel.com,
	lee.jones@...aro.org, patches@...nsource.wolfsonmicro.com,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 2/3] gadget: Introduce the usb charger framework

On Fri, Aug 14, 2015 at 05:47:45PM +0800, 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.
> 
> 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@...aro.org>
> ---
>  drivers/usb/gadget/Kconfig      |    7 +
>  drivers/usb/gadget/Makefile     |    1 +
>  drivers/usb/gadget/charger.c    |  561 +++++++++++++++++++++++++++++++++++++++
>  include/linux/usb/usb_charger.h |  145 ++++++++++
>  4 files changed, 714 insertions(+)
>  create mode 100644 drivers/usb/gadget/charger.c
>  create mode 100644 include/linux/usb/usb_charger.h
> 
> diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
> index bcf83c0..3d2b959 100644
> --- a/drivers/usb/gadget/Kconfig
> +++ b/drivers/usb/gadget/Kconfig
> @@ -127,6 +127,13 @@ config USB_GADGET_STORAGE_NUM_BUFFERS
>  	   a module parameter as well.
>  	   If unsure, say 2.
>  
> +config USB_CHARGER
> +	bool "USB charger support"
> +	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/Makefile b/drivers/usb/gadget/Makefile
> index 598a67d..1e421c1 100644
> --- a/drivers/usb/gadget/Makefile
> +++ b/drivers/usb/gadget/Makefile
> @@ -10,3 +10,4 @@ libcomposite-y			:= usbstring.o config.o epautoconf.o
>  libcomposite-y			+= composite.o functions.o configfs.o u_f.o
>  
>  obj-$(CONFIG_USB_GADGET)	+= udc/ function/ legacy/
> +obj-$(CONFIG_USB_CHARGER)	+= charger.o
> diff --git a/drivers/usb/gadget/charger.c b/drivers/usb/gadget/charger.c
> new file mode 100644
> index 0000000..f24f7b7
> --- /dev/null
> +++ b/drivers/usb/gadget/charger.c
> @@ -0,0 +1,561 @@
> +/*
> + * usb charger.c -- USB charger driver

I think your company also wants a copyright line here.  Not that it
means anything at all, but some lawyers love cargo-cult text blobs.


> + *
> + * 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.

I have to ask, do you really mean "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 DEFINE_IDA(usb_charger_ida);
> +static struct bus_type usb_charger_subsys = {
> +	.name           = "usb-charger",
> +	.dev_name       = "usb-charger",
> +};
> +
> +static struct usb_charger *dev_to_uchger(struct device *udev)
> +{
> +	return container_of(udev, struct usb_charger, dev);
> +}
> +
> +static ssize_t usb_charger_cur_show(struct device *dev,
> +				    struct device_attribute *attr,
> +				    char *buf)
> +{
> +	struct usb_charger *uchger = dev_to_uchger(dev);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%d %d %d %d\n",
> +			 uchger->cur_limit.sdp_cur_limit,
> +			 uchger->cur_limit.dcp_cur_limit,
> +			 uchger->cur_limit.cdp_cur_limit,
> +			 uchger->cur_limit.aca_cur_limit);
> +}
> +
> +static ssize_t usb_charger_cur_store(struct device *dev,
> +				     struct device_attribute *attr,
> +				     const char *buf, size_t count)
> +{
> +	struct usb_charger *uchger = dev_to_uchger(dev);
> +	struct usb_charger_cur_limit cur;
> +	int ret;
> +
> +	ret = sscanf(buf, "%d %d %d %d",
> +		     &cur.sdp_cur_limit, &cur.dcp_cur_limit,
> +		     &cur.cdp_cur_limit, &cur.aca_cur_limit);
> +	if (ret == 0)
> +		return -EINVAL;
> +
> +	ret = usb_charger_set_cur_limit(uchger, &cur);
> +	if (ret < 0)
> +		return ret;
> +
> +	return count;
> +}
> +static DEVICE_ATTR(cur_limit, 0644, usb_charger_cur_show, usb_charger_cur_store);

DEVICE_ATTR_RW()?

> +
> +static struct attribute *uchger_attributes[] = {
> +	&dev_attr_cur_limit.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group uchger_attr_group = {
> +	.attrs = uchger_attributes,
> +};

ATTRIBUTE_GROUPS()?

> +
> +/*
> + * usb_charger_find_by_name - Get the usb charger device by name.
> + * @name - usb charger device name.
> + *
> + * return the instance of usb charger device, the device must be
> + * released with usb_charger_put().
> + */
> +struct usb_charger *usb_charger_find_by_name(const char *name)
> +{
> +	struct device *udev;
> +
> +	if (!name)
> +		return ERR_PTR(-EINVAL);
> +
> +	udev = bus_find_device_by_name(&usb_charger_subsys, NULL, name);
> +	if (!udev)
> +		return ERR_PTR(-ENODEV);
> +
> +	return dev_to_uchger(udev);
> +}
> +
> +/*
> + * usb_charger_get() - Reference a usb charger.
> + * @uchger - usb charger
> + */
> +struct usb_charger *usb_charger_get(struct usb_charger *uchger)
> +{
> +	return (uchger && get_device(&uchger->dev)) ? uchger : NULL;
> +}
> +
> +/*
> + * usb_charger_put() - Dereference a usb charger.
> + * @uchger - charger to release
> + */
> +void usb_charger_put(struct usb_charger *uchger)
> +{
> +	if (uchger)
> +		put_device(&uchger->dev);
> +}
> +
> +/*
> + * usb_charger_register_notify() - Register a notifiee to get notified by
> + * any attach status changes from the usb charger detection.
> + * @uchger - the usb charger device 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)
> +		return -EINVAL;
> +
> +	mutex_lock(&uchger->lock);
> +	ret = raw_notifier_chain_register(&uchger->uchger_nh, nb);
> +
> +	/* Generate an initial notify so users start in the right state */
> +	if (!ret) {
> +		usb_charger_detect_type(uchger);
> +		raw_notifier_call_chain(&uchger->uchger_nh,
> +					usb_charger_get_cur_limit(uchger),
> +					uchger);
> +	}
> +	mutex_unlock(&uchger->lock);
> +
> +	return ret;
> +}
> +
> +/*
> + * 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.
> + */
> +int usb_charger_unregister_notify(struct usb_charger *uchger,
> +				  struct notifier_block *nb)
> +{
> +	int ret;
> +
> +	if (!uchger || !nb)
> +		return -EINVAL;
> +
> +	mutex_lock(&uchger->lock);
> +	ret = raw_notifier_chain_unregister(&uchger->uchger_nh, nb);
> +	mutex_unlock(&uchger->lock);
> +
> +	return ret;
> +}
> +
> +/*
> + * usb_charger_detect_type() - Get the usb charger type by the callback
> + * which is implemented by gadget operations.
> + * @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_set_cur_limit() - Set the current limitation.
> + * @uchger - the usb charger device.
> + * @cur_limit_set - the current limitation.
> + */
> +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.
> + *
> + * return the current limitation to set.
> + */
> +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_notifier_others() - It will notify other device registered
> + * on usb charger when the usb charger state is changed.
> + * @uchger - the usb charger device.
> + * @state - the state of the usb charger.
> + */
> +static void
> +usb_charger_notify_others(struct usb_charger *uchger,
> +			  enum usb_charger_state state)
> +{
> +	mutex_lock(&uchger->lock);
> +	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;
> +	}
> +	mutex_unlock(&uchger->lock);
> +}
> +
> +/*
> + * 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 (!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.
> + * @nb - the notifier block that notified by usb gadget device.
> + * @state - the usb gadget state.
> + * @data - here specify a usb gadget 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);
> +
> +	kfree(uchger->name);
> +	kfree(uchger);
> +}
> +
> +/*
> + * usb_charger_unregister() - Unregister a usb charger device.
> + * @uchger - the usb charger to be unregistered.
> + */
> +static int usb_charger_unregister(struct usb_charger *uchger)
> +{
> +	if (!uchger)
> +		return -EINVAL;
> +
> +	sysfs_remove_group(&uchger->dev.kobj, &uchger_attr_group);
> +	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
> + * which is created by the usb charger framework.
> + * @uchger - the new usb charger device.
> + */
> +static int usb_charger_register(struct device *dev, struct usb_charger *uchger)
> +{
> +	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;
> +	uchger->dev.bus = &usb_charger_subsys;
> +
> +	ret = ida_simple_get(&usb_charger_ida, 0, 0, GFP_KERNEL);
> +	if (ret < 0) {
> +		dev_err(dev, "get usb charger id failed\n");
> +		return ret;
> +	}
> +
> +	uchger->id = ret;
> +	dev_set_name(&uchger->dev, "usb-charger.%d", uchger->id);
> +	dev_set_drvdata(&uchger->dev, uchger);
> +
> +	ret = device_register(&uchger->dev);
> +	if (ret)
> +		goto fail_register;
> +
> +	ret = sysfs_create_group(&uchger->dev.kobj, &uchger_attr_group);

And you just raced with userspace, and lost :(

Assign the group to the device _before_ you tell userspace about it.

The big hint here that is wrong is that you have to call a sysfs_*
function for a struct device.  There is no device_create_group() call
for a reason.



> +	if (ret)
> +		goto fail_create_files;
> +
> +	return 0;
> +
> +fail_create_files:
> +	device_unregister(&uchger->dev);
> +fail_register:
> +	put_device(&uchger->dev);
> +	ida_simple_remove(&usb_charger_ida, uchger->id);
> +	uchger->id = -1;
> +	dev_err(dev, "Failed to register usb charger (%s)\n",
> +		uchger->name);
> +	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];

That's a lot of stack, why?

> +	char *str;
> +	int ret;
> +
> +	if (!ugadget)
> +		return -EINVAL;
> +
> +	uchger = devm_kzalloc(&ugadget->dev, sizeof(struct usb_charger),
> +			      GFP_KERNEL);

No, you are creating a new struct device, you can't assign its resources
to another struct device, that breaks all of the lifetime rules.
kzalloc() only please.

> +	if (!uchger)
> +		return -ENOMEM;
> +
> +	sprintf(buf, "usb-charger.%s", ugadget->name);
> +	str = devm_kzalloc(&ugadget->dev, sizeof(char) * (strlen(buf) + 1),
> +			   GFP_KERNEL);

Why have a string when you already have a name for the device, in the
device itself?  What is this all for?


> +	if (!str)
> +		return -ENOMEM;
> +
> +	strcpy(str, buf);
> +	uchger->name = str;
> +	uchger->type = UNKNOWN_TYPE;
> +	uchger->state = USB_CHARGER_DEFAULT;
> +	uchger->id = -1;
> +	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;
> +
> +	mutex_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;
> +		extcon_register_notifier(edev, EXTCON_USB, &uchger->extcon_nb.nb);
> +	}
> +
> +	/* 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_gadget_register_notify(ugadget, &uchger->gadget_nb);
> +
> +	/* register a new usb charger */
> +	ret = usb_charger_register(&ugadget->dev, uchger);
> +	if (ret)
> +		goto fail;
> +
> +	return 0;
> +
> +fail:
> +	if (uchger->extcon_dev)
> +		extcon_unregister_notifier(uchger->extcon_dev,
> +					   EXTCON_USB, &uchger->extcon_nb.nb);
> +
> +	usb_gadget_unregister_notify(uchger->gadget, &uchger->gadget_nb);
> +	return ret;
> +}
> +
> +int usb_charger_exit(struct usb_gadget *ugadget)
> +{
> +	struct usb_charger *uchger = ugadget->uchger;
> +
> +	if (!uchger)
> +		return -EINVAL;
> +
> +	if (uchger->extcon_dev)
> +		extcon_unregister_notifier(uchger->extcon_dev,
> +					   EXTCON_USB, &uchger->extcon_nb.nb);
> +
> +	usb_gadget_unregister_notify(uchger->gadget, &uchger->gadget_nb);
> +	ida_simple_remove(&usb_charger_ida, uchger->id);
> +
> +	return usb_charger_unregister(uchger);
> +}
> +
> +static int __init usb_charger_sysfs_init(void)
> +{
> +	return subsys_system_register(&usb_charger_subsys, NULL);
> +}
> +core_initcall(usb_charger_sysfs_init);
> +
> +MODULE_AUTHOR("Baolin Wang <baolin.wang@...aro.org>");
> +MODULE_DESCRIPTION("USB charger driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/usb/usb_charger.h b/include/linux/usb/usb_charger.h
> new file mode 100644
> index 0000000..8cbfaae
> --- /dev/null
> +++ b/include/linux/usb/usb_charger.h
> @@ -0,0 +1,145 @@
> +#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. */

Heh, as if people read comments :(

> +	const char		*name;

This isn't needed, use the one in your struct device.

> +	struct device		dev;
> +	struct raw_notifier_head	uchger_nh;
> +	struct list_head	entry;

Why do you need another list?  The device already is on a list.

> +	struct mutex		lock;

What is this protecting, document it.

thanks,

greg k-h
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