leds-gpio driver 续1

最新推荐文章于 2025-06-23 16:51:26 发布

feiwatson

最新推荐文章于 2025-06-23 16:51:26 发布

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分类专栏： Linux Raspberry 树莓派驱动

本文链接：https://blog.youkuaiyun.com/feiwatson/article/details/80871500

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本文详细解析了Linux内核中GPIO LED模块的工作原理，特别是如何通过设备树配置实现LED设备的初始化与控制。文章深入分析了gpio-ledplatform_device与gpio-ledplatform_driver的匹配过程，以及关键函数gpio_led_probe和gpio_leds_create的具体实现。

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在上文中分析了gpio-led platform_device是如何定义并注册的。
那么gpio-led platform_device 和 gpio-led platform_driver是如何匹配的呢

我们还是先分析probe函数
drivers\leds\leds-gpio.c

static int gpio_led_probe(struct platform_device *pdev)
{
    struct gpio_led_platform_data *pdata = dev_get_platdata(&pdev->dev);
    struct gpio_leds_priv *priv;
    int i, ret = 0;

    if (pdata && pdata->num_leds) {
        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);
        if (IS_ERR(priv))
            return PTR_ERR(priv);
    }

    platform_set_drvdata(pdev, priv);

    return 0;
}

接着看gpio_leds_create()函数

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);
    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];
        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);
        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);
        if (ret < 0) {
            fwnode_handle_put(child);
            return ERR_PTR(ret);
        }
        led_dat->cdev.dev->of_node = np;
        priv->num_leds++;
    }
    return priv;
}

其中，

ret = fwnode_property_read_string(child, "label", &led.name);

led.gpiod = devm_fwnode_get_gpiod_from_child(dev, NULL, child,
                                 GPIOD_ASIS,
                                 led.name);

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

最后调用create_gpio_led()函数创建led

ret = create_gpio_led(&led, led_dat, dev, np, NULL);

那么设备树中的gpio定义是如何传递到设备中的呢
接着分析gpio_leds_create中调用的devm_fwnode_get_gpiod_from_child()函数
先看一段定义
drivers/gpio/gpiolib.h

/* gpio suffixes used for ACPI and device tree lookup */
static const char * const gpio_suffixes[] = { "gpios", "gpio" };

devm_fwnode_get_gpiod_from_child调用一系列函数，创建gpio_desc

fwnode_get_named_gpiod
gpiod_get_from_of_node

最后调用devres_add将gpio_desc作为device resource 注册给leds-gpio platfor_device

devres_add(dev, dr);