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    Subject[PATCH v5 2/5] Extcon: support notification based on the state changes.
    Date
    From: Donggeun Kim <dg77.kim@samsung.com>

    State changes of extcon devices have been notified via kobjet_uevent.
    This patch adds notifier interfaces in order to allow device drivers to
    get notified easily. Along with notifier interface,
    extcon_get_extcon_dev() function is added so that device drivers may
    discover a extcon_dev easily.

    Signed-off-by: Donggeun Kim <dg77.kim@samsung.com>
    Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
    Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

    --
    Changes from RFC
    - Renamed switch to extcon
    - Bugfix: extcon_dev_unregister()
    - Bugfix: "edev->dev" is "internal" data.
    - Added kerneldoc comments.
    - Reworded comments.
    ---
    drivers/extcon/extcon_class.c | 66 +++++++++++++++++++++++++++++++++++++++++
    include/linux/extcon.h | 38 +++++++++++++++++++++++
    2 files changed, 104 insertions(+), 0 deletions(-)

    diff --git a/drivers/extcon/extcon_class.c b/drivers/extcon/extcon_class.c
    index 9d29c79..763cf4d 100644
    --- a/drivers/extcon/extcon_class.c
    +++ b/drivers/extcon/extcon_class.c
    @@ -34,6 +34,9 @@
    struct class *extcon_class;
    struct class *extcon_class_for_android;

    +static LIST_HEAD(extcon_dev_list);
    +static DEFINE_MUTEX(extcon_dev_list_lock);
    +
    static ssize_t state_show(struct device *dev, struct device_attribute *attr,
    char *buf)
    {
    @@ -73,6 +76,9 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
    * the name of extcon device (envp[0]) and the state output (envp[1]).
    * Tizen uses this format for extcon device to get events from ports.
    * Android uses this format as well.
    + *
    + * Note that notifier provides the which bits are changes in the state
    + * variable with "val" to the callback.
    */
    void extcon_set_state(struct extcon_dev *edev, u32 state)
    {
    @@ -82,10 +88,14 @@ void extcon_set_state(struct extcon_dev *edev, u32 state)
    char *envp[3];
    int env_offset = 0;
    int length;
    + u32 old_state = edev->state;

    if (edev->state != state) {
    edev->state = state;

    + raw_notifier_call_chain(&edev->nh, old_state ^ edev->state,
    + edev);
    +
    prop_buf = (char *)get_zeroed_page(GFP_KERNEL);
    if (prop_buf) {
    length = name_show(edev->dev, NULL, prop_buf);
    @@ -115,6 +125,51 @@ void extcon_set_state(struct extcon_dev *edev, u32 state)
    }
    EXPORT_SYMBOL_GPL(extcon_set_state);

    +/**
    + * extcon_get_extcon_dev() - Get the extcon device instance from the name
    + * @extcon_name: The extcon name provided with extcon_dev_register()
    + */
    +struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
    +{
    + struct extcon_dev *sd;
    +
    + mutex_lock(&extcon_dev_list_lock);
    + list_for_each_entry(sd, &extcon_dev_list, entry) {
    + if (!strcmp(sd->name, extcon_name))
    + goto out;
    + }
    + sd = NULL;
    +out:
    + mutex_unlock(&extcon_dev_list_lock);
    + return sd;
    +}
    +EXPORT_SYMBOL_GPL(extcon_get_extcon_dev);
    +
    +/**
    + * extcon_register_notifier() - Register a notifee to get notified by
    + * any attach status changes from the extcon.
    + * @edev: the extcon device.
    + * @nb: a notifier block to be registered.
    + */
    +int extcon_register_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb)
    +{
    + return raw_notifier_chain_register(&edev->nh, nb);
    +}
    +EXPORT_SYMBOL_GPL(extcon_register_notifier);
    +
    +/**
    + * extcon_unregister_notifier() - Unregister a notifee from the extcon device.
    + * @edev: the extcon device.
    + * @nb: a registered notifier block to be unregistered.
    + */
    +int extcon_unregister_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb)
    +{
    + return raw_notifier_chain_unregister(&edev->nh, nb);
    +}
    +EXPORT_SYMBOL_GPL(extcon_unregister_notifier);
    +
    static struct device_attribute extcon_attrs[] = {
    __ATTR_RO(state),
    __ATTR_RO(name),
    @@ -145,6 +200,10 @@ static int create_extcon_class_for_android(void)

    static void extcon_cleanup(struct extcon_dev *edev, bool skip)
    {
    + mutex_lock(&extcon_dev_list_lock);
    + list_del(&edev->entry);
    + mutex_unlock(&extcon_dev_list_lock);
    +
    if (!skip && get_device(edev->dev)) {
    device_unregister(edev->dev);
    put_device(edev->dev);
    @@ -200,8 +259,15 @@ int extcon_dev_register(struct extcon_dev *edev, struct device *dev)
    goto err_dev;
    }

    + RAW_INIT_NOTIFIER_HEAD(&edev->nh);
    +
    dev_set_drvdata(edev->dev, edev);
    edev->state = 0;
    +
    + mutex_lock(&extcon_dev_list_lock);
    + list_add(&edev->entry, &extcon_dev_list);
    + mutex_unlock(&extcon_dev_list_lock);
    +
    return 0;

    err_dev:
    diff --git a/include/linux/extcon.h b/include/linux/extcon.h
    index da0bbc8..1e47e3b 100644
    --- a/include/linux/extcon.h
    +++ b/include/linux/extcon.h
    @@ -23,6 +23,7 @@
    #ifndef __LINUX_EXTCON_H__
    #define __LINUX_EXTCON_H__

    +#include <linux/notifier.h>
    /**
    * struct extcon_dev - An extcon device represents one external connector.
    * @name The name of this extcon device. Parent device name is used
    @@ -37,6 +38,9 @@
    * @dev Device of this extcon. Do not provide at register-time.
    * @state Attach/detach state of this extcon. Do not provide at
    * register-time
    + * @nh Notifier for the state change events from this extcon
    + * @entry To support list of extcon devices so that uses can search
    + * for extcon devices based on the extcon name.
    *
    * In most cases, users only need to provide "User initializing data" of
    * this struct when registering an extcon. In some exceptional cases,
    @@ -55,6 +59,8 @@ struct extcon_dev {
    /* --- Internal data. Please do not set. --- */
    struct device *dev;
    u32 state;
    + struct raw_notifier_head nh;
    + struct list_head entry;
    };

    /**
    @@ -76,8 +82,14 @@ struct gpio_extcon_platform_data {
    };

    #ifdef CONFIG_EXTCON
    +
    +/*
    + * Following APIs are for notifiers or configurations.
    + * Notifiers are the external port and connection devices.
    + */
    extern int extcon_dev_register(struct extcon_dev *edev, struct device *dev);
    extern void extcon_dev_unregister(struct extcon_dev *edev);
    +extern struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name);

    static inline u32 extcon_get_state(struct extcon_dev *edev)
    {
    @@ -85,6 +97,15 @@ static inline u32 extcon_get_state(struct extcon_dev *edev)
    }

    extern void extcon_set_state(struct extcon_dev *edev, u32 state);
    +
    +/*
    + * Following APIs are to monitor every action of a notifier.
    + * Registerer gets notified for every external port of a connection device.
    + */
    +extern int extcon_register_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb);
    +extern int extcon_unregister_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb);
    #else /* CONFIG_EXTCON */
    static inline int extcon_dev_register(struct extcon_dev *edev,
    struct device *dev)
    @@ -100,5 +121,22 @@ static inline u32 extcon_get_state(struct extcon_dev *edev)
    }

    static inline void extcon_set_state(struct extcon_dev *edev, u32 state) { }
    +static inline struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
    +{
    + return NULL;
    +}
    +
    +static inline int extcon_register_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb)
    +{
    + return 0;
    +}
    +
    +static inline int extcon_unregister_notifier(struct extcon_dev *edev,
    + struct notifier_block *nb)
    +{
    + return 0;
    +}
    +
    #endif /* CONFIG_EXTCON */
    #endif /* __LINUX_EXTCON_H__ */
    --
    1.7.4.1


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