【LED子系统深度剖析】三、硬件驱动层详解 #

struct gpio_led_platform_data {
    int 		num_leds;
    const struct gpio_led *leds;

#define GPIO_LED_NO_BLINK_LOW	0	/* No blink GPIO state low */
#define GPIO_LED_NO_BLINK_HIGH	1	/* No blink GPIO state high */
#define GPIO_LED_BLINK		2	/* Please, blink */
    gpio_blink_set_t	gpio_blink_set;
};

struct gpio_leds_priv {
    int num_leds;
    struct gpio_led_data leds[];
};

static int gpio_led_probe(struct platform_device *pdev)
{
    struct gpio_led_platform_data *pdata = dev_get_platdata(&pdev->dev);		//	检索设备的平台数据
    struct gpio_leds_priv *priv;
    int i, ret = 0;

    if (pdata && pdata->num_leds) {												//	判断平台数据LED数量
        priv = devm_kzalloc(&pdev->dev,
                sizeof_gpio_leds_priv(pdata->num_leds),
                    GFP_KERNEL);
        if (!priv)
            return -ENOMEM;

        priv->num_leds = pdata->num_leds;
        for (i = 0; i < priv->num_leds; i++) {
            ret = create_gpio_led(&pdata->leds[i], &priv->leds[i],
                          &pdev->dev, NULL,
                          pdata->gpio_blink_set);
            if (ret < 0)
                return ret;
        }
    } else {
        priv = gpio_leds_create(pdev);											//	创建LED设备	
        if (IS_ERR(priv))
            return PTR_ERR(priv);
    }

    platform_set_drvdata(pdev, priv);

    return 0;
}

/* For the leds-gpio driver */
struct gpio_led {
    const char *name;					// LED名称
    const char *default_trigger;		// 默认触发类型	
    unsigned 	gpio;					// GPIO编号
    unsigned	active_low : 1;			// 低电平有效
    unsigned	retain_state_suspended : 1;
    unsigned	panic_indicator : 1;
    unsigned	default_state : 2;		// 默认状态
    unsigned	retain_state_shutdown : 1;
    /* default_state should be one of LEDS_GPIO_DEFSTATE_(ON|OFF|KEEP) */
    struct gpio_desc *gpiod;			// GPIO Group
};

struct gpio_led_data {
    struct led_classdev cdev;		// LED Class
    struct gpio_desc *gpiod;		// GPIO description
    u8 can_sleep;					
    u8 blinking;					// 闪烁
    gpio_blink_set_t platform_gpio_blink_set;	// 闪烁设置
};

static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
{
    struct device *dev = &pdev->dev;
    struct fwnode_handle *child;
    struct gpio_leds_priv *priv;
    int count, ret;

    count = device_get_child_node_count(dev);		//	获取子节点数量
    if (!count)
        return ERR_PTR(-ENODEV);

    priv = devm_kzalloc(dev, sizeof_gpio_leds_priv(count), GFP_KERNEL);
    if (!priv)
        return ERR_PTR(-ENOMEM);

    device_for_each_child_node(dev, child) {
        struct gpio_led_data *led_dat = &priv->leds[priv->num_leds];	//	与gpio_leds_priv结构体关联
        struct gpio_led led = {};
        const char *state = NULL;
        struct device_node *np = to_of_node(child);

        ret = fwnode_property_read_string(child, "label", &led.name);	//	读设备树属性，赋值gpio_led结构体
        if (ret && IS_ENABLED(CONFIG_OF) && np)
            led.name = np->name;
        if (!led.name) {
            fwnode_handle_put(child);
            return ERR_PTR(-EINVAL);
        }

        led.gpiod = devm_fwnode_get_gpiod_from_child(dev, NULL, child,
                                 GPIOD_ASIS,
                                 led.name);
        if (IS_ERR(led.gpiod)) {
            fwnode_handle_put(child);
            return ERR_CAST(led.gpiod);
        }

        fwnode_property_read_string(child, "linux,default-trigger",
                        &led.default_trigger);

        if (!fwnode_property_read_string(child, "default-state",
                         &state)) {
            if (!strcmp(state, "keep"))
                led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
            else if (!strcmp(state, "on"))
                led.default_state = LEDS_GPIO_DEFSTATE_ON;
            else
                led.default_state = LEDS_GPIO_DEFSTATE_OFF;
        }

        if (fwnode_property_present(child, "retain-state-suspended"))
            led.retain_state_suspended = 1;
        if (fwnode_property_present(child, "retain-state-shutdown"))
            led.retain_state_shutdown = 1;
        if (fwnode_property_present(child, "panic-indicator"))
            led.panic_indicator = 1;

        ret = create_gpio_led(&led, led_dat, dev, np, NULL);	//	将gpio_led结构体、gpio_led_data关联起来
        if (ret < 0) {
            fwnode_handle_put(child);
            return ERR_PTR(ret);
        }
        led_dat->cdev.dev->of_node = np;
        priv->num_leds++;
    }

    return priv;
}

struct led_classdev {
    const char		*name;
    enum led_brightness	 brightness;
    enum led_brightness	 max_brightness;
    int			 flags;

    /* Lower 16 bits reflect status */
#define LED_SUSPENDED		BIT(0)
#define LED_UNREGISTERING	BIT(1)
    /* Upper 16 bits reflect control information */
#define LED_CORE_SUSPENDRESUME	BIT(16)
#define LED_SYSFS_DISABLE	BIT(17)
#define LED_DEV_CAP_FLASH	BIT(18)
#define LED_HW_PLUGGABLE	BIT(19)
#define LED_PANIC_INDICATOR	BIT(20)
#define LED_BRIGHT_HW_CHANGED	BIT(21)
#define LED_RETAIN_AT_SHUTDOWN	BIT(22)

    /* set_brightness_work / blink_timer flags, atomic, private. */
    unsigned long		work_flags;

#define LED_BLINK_SW			0
#define LED_BLINK_ONESHOT		1
#define LED_BLINK_ONESHOT_STOP		2
#define LED_BLINK_INVERT		3
#define LED_BLINK_BRIGHTNESS_CHANGE 	4
#define LED_BLINK_DISABLE		5

    /* Set LED brightness level
     * Must not sleep. Use brightness_set_blocking for drivers
     * that can sleep while setting brightness.
     */
    void		(*brightness_set)(struct led_classdev *led_cdev,
                      enum led_brightness brightness);
    /*
     * Set LED brightness level immediately - it can block the caller for
     * the time required for accessing a LED device register.
     */
    int (*brightness_set_blocking)(struct led_classdev *led_cdev,
                       enum led_brightness brightness);
    /* Get LED brightness level */
    enum led_brightness (*brightness_get)(struct led_classdev *led_cdev);

    /*
     * Activate hardware accelerated blink, delays are in milliseconds
     * and if both are zero then a sensible default should be chosen.
     * The call should adjust the timings in that case and if it can't
     * match the values specified exactly.
     * Deactivate blinking again when the brightness is set to LED_OFF
     * via the brightness_set() callback.
     */
    int		(*blink_set)(struct led_classdev *led_cdev,
                     unsigned long *delay_on,
                     unsigned long *delay_off);

    struct device		*dev;
    const struct attribute_group	**groups;

    struct list_head	 node;			/* LED Device list */
    const char		*default_trigger;	/* Trigger to use */

    unsigned long		 blink_delay_on, blink_delay_off;
    struct timer_list	 blink_timer;
    int			 blink_brightness;
    int			 new_blink_brightness;
    void			(*flash_resume)(struct led_classdev *led_cdev);

    struct work_struct	set_brightness_work;
    int			delayed_set_value;

#ifdef CONFIG_LEDS_TRIGGERS
    /* Protects the trigger data below */
    struct rw_semaphore	 trigger_lock;

    struct led_trigger	*trigger;
    struct list_head	 trig_list;
    void			*trigger_data;
    /* true if activated - deactivate routine uses it to do cleanup */
    bool			activated;
#endif

#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
    int			 brightness_hw_changed;
    struct kernfs_node	*brightness_hw_changed_kn;
#endif

    /* Ensures consistent access to the LED Flash Class device */
    struct mutex		led_access;
};

static int create_gpio_led(const struct gpio_led *template,
    struct gpio_led_data *led_dat, struct device *parent,
    struct device_node *np, gpio_blink_set_t blink_set)
{
    int ret, state;

    led_dat->gpiod = template->gpiod;
    if (!led_dat->gpiod) {
        /*
         * This is the legacy code path for platform code that
         * still uses GPIO numbers. Ultimately we would like to get
         * rid of this block completely.
         */
        unsigned long flags = GPIOF_OUT_INIT_LOW;

        /* skip leds that aren't available */
        if (!gpio_is_valid(template->gpio)) {								//	判断是否gpio合法
            dev_info(parent, "Skipping unavailable LED gpio %d (%s)\n",
                    template->gpio, template->name);
            return 0;
        }

        if (template->active_low)
            flags |= GPIOF_ACTIVE_LOW;

        ret = devm_gpio_request_one(parent, template->gpio, flags,
                        template->name);
        if (ret < 0)
            return ret;

        led_dat->gpiod = gpio_to_desc(template->gpio);						//	获取gpio组
        if (!led_dat->gpiod)
            return -EINVAL;
    }

    led_dat->cdev.name = template->name;									//	赋值一些属性信息
    led_dat->cdev.default_trigger = template->default_trigger;
    led_dat->can_sleep = gpiod_cansleep(led_dat->gpiod);
    if (!led_dat->can_sleep)
        led_dat->cdev.brightness_set = gpio_led_set;						//	设置LED
    else
        led_dat->cdev.brightness_set_blocking = gpio_led_set_blocking;
    led_dat->blinking = 0;
    if (blink_set) {
        led_dat->platform_gpio_blink_set = blink_set;
        led_dat->cdev.blink_set = gpio_blink_set;
    }
    if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP) {
        state = gpiod_get_value_cansleep(led_dat->gpiod);
        if (state < 0)
            return state;
    } else {
        state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
    }
    led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
    if (!template->retain_state_suspended)
        led_dat->cdev.flags |= LED_CORE_SUSPENDRESUME;
    if (template->panic_indicator)
        led_dat->cdev.flags |= LED_PANIC_INDICATOR;
    if (template->retain_state_shutdown)
        led_dat->cdev.flags |= LED_RETAIN_AT_SHUTDOWN;

    ret = gpiod_direction_output(led_dat->gpiod, state);
    if (ret < 0)
        return ret;

    return devm_of_led_classdev_register(parent, np, &led_dat->cdev);		//	将LED设备注册到子系统中
}

static int gpio_blink_set(struct led_classdev *led_cdev,
    unsigned long *delay_on, unsigned long *delay_off)
{
    struct gpio_led_data *led_dat = cdev_to_gpio_led_data(led_cdev);

    led_dat->blinking = 1;
    return led_dat->platform_gpio_blink_set(led_dat->gpiod, GPIO_LED_BLINK,
                        delay_on, delay_off);
}

static inline struct gpio_led_data *
            cdev_to_gpio_led_data(struct led_classdev *led_cdev)
{
    return container_of(led_cdev, struct gpio_led_data, cdev);
}

static void gpio_led_set(struct led_classdev *led_cdev,
    enum led_brightness value)
{
    struct gpio_led_data *led_dat = cdev_to_gpio_led_data(led_cdev);
    int level;

    if (value == LED_OFF)
        level = 0;
    else
        level = 1;

    if (led_dat->blinking) {
        led_dat->platform_gpio_blink_set(led_dat->gpiod, level,
                         NULL, NULL);
        led_dat->blinking = 0;
    } else {
        if (led_dat->can_sleep)
            gpiod_set_value_cansleep(led_dat->gpiod, level);
        else
            gpiod_set_value(led_dat->gpiod, level);
    }
}

static int gpio_led_set_blocking(struct led_classdev *led_cdev,
    enum led_brightness value)
{
    gpio_led_set(led_cdev, value);
    return 0;
}

gpio_led_probe(drivers/leds/leds-gpio.c)
    |--> gpio_leds_create
        |--> create_gpio_led            //  创建LED设备
            |--> devm_of_led_classdev_register