leds-gpio驱动分析

#include
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struct gpio_led_data {
struct led_classdev cdev;
unsigned gpio;
struct work_struct work;
u8 new_level;
u8 can_sleep;
u8 active_low;//表示灯亮时是低电平，则active low为真即1。
u8 blinking;
int (*platform_gpio_blink_set)(unsigned gpio, int state,
unsigned long *delay_on, unsigned long *delay_off);
};

static void gpio_led_work(struct work_struct *work)
{
struct gpio_led_data *led_dat =
container_of(work, struct gpio_led_data, work);

if (led_dat->blinking) {//如果led的闪烁标志位被置位，则设置下灯的亮灭。
led_dat->platform_gpio_blink_set(led_dat->gpio,
led_dat->new_level,
NULL, NULL);
led_dat->blinking = 0;//设置完led的亮灭后同时清除led的闪烁标志位。
} else
gpio_set_value_cansleep(led_dat->gpio, led_dat->new_level);
}

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

if (value == LED_OFF)//根据亮度属性brightness设置level值。
level = 0;
else
level = 1;


if (led_dat->active_low)
level = !level;


/* Setting GPIOs with I2C/etc requires a task context, and we don't
* seem to have a reliable way to know if we're already in one; so
* let's just assume the worst.
*/
if (led_dat->can_sleep) {//如果该gpio口处于sleep，则将控制亮灭的level值暂时存储。
led_dat->new_level = level;
schedule_work(&led_dat->work);
} else {
if (led_dat->blinking) {//如果该gpio口未sleep，则直接判断闪烁标志位并设置下灯的亮灭。
led_dat->platform_gpio_blink_set(led_dat->gpio, level,
NULL, NULL);
led_dat->blinking = 0;
} else
gpio_set_value(led_dat->gpio, level);//若闪烁标志位未被置位，则直接设置gpio口的高低电平??
}
}

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

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

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

led_dat->gpio = -1;

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

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

led_dat->cdev.name = template->name;//创建的dev节点的名字由你的平台设备的信息决定的。
//template有对应于pdata->leds[i]，struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
led_dat->cdev.default_trigger = template->default_trigger;
led_dat->gpio = template->gpio;
led_dat->can_sleep = gpio_cansleep(template->gpio);
led_dat->active_low = template->active_low;
led_dat->blinking = 0;
if (blink_set) {
led_dat->platform_gpio_blink_set = blink_set;
led_dat->cdev.blink_set = gpio_blink_set;
}
led_dat->cdev.brightness_set = gpio_led_set;
if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP)
state = !!gpio_get_value_cansleep(led_dat->gpio) ^ led_dat->active_low;
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;

ret = gpio_direction_output(led_dat->gpio, led_dat->active_low ^ state);
if (ret < 0)//设置该gpio口作为输入口还是输出口。
return ret;

INIT_WORK(&led_dat->work, gpio_led_work);

ret = led_classdev_register(parent, &led_dat->cdev);
if (ret < 0)//在/sys/class/leds目录下创建若干led节点(sys_led  wan_led等)
return ret;///sys/class/leds目录是在系统启动start_kernel.....时创建的。

return 0;
}

static void delete_gpio_led(struct gpio_led_data *led)
{
if (!gpio_is_valid(led->gpio))
return;
led_classdev_unregister(&led->cdev);//注销就是将/sys/class/leds目录下创建的若干led节点删除，同时取消工作队列即可。
cancel_work_sync(&led->work);
}

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

static inline int sizeof_gpio_leds_priv(int num_leds)
{
return sizeof(struct gpio_leds_priv) +
(sizeof(struct gpio_led_data) * num_leds);
}

/* Code to create from OpenFirmware platform devices */
#ifdef CONFIG_OF_GPIO
static struct gpio_leds_priv *gpio_leds_create_of(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node, *child;
struct gpio_leds_priv *priv;
int count, ret;

/* count LEDs in this device, so we know how much to allocate */
count = of_get_child_count(np);
if (!count)
return ERR_PTR(-ENODEV);

for_each_child_of_node(np, child)
if (of_get_gpio(child, 0) == -EPROBE_DEFER)
return ERR_PTR(-EPROBE_DEFER);

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

for_each_child_of_node(np, child) {
struct gpio_led led = {};
enum of_gpio_flags flags;
const char *state;

led.gpio = of_get_gpio_flags(child, 0, &flags);
led.active_low = flags & OF_GPIO_ACTIVE_LOW;
led.name = of_get_property(child, "label", NULL) ? : child->name;
led.default_trigger =
of_get_property(child, "linux,default-trigger", NULL);
state = of_get_property(child, "default-state", NULL);
if (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;
}

ret = create_gpio_led(&led, &priv->leds[priv->num_leds++],
     &pdev->dev, NULL);
if (ret < 0) {
of_node_put(child);
goto err;
}
}

return priv;

err:
for (count = priv->num_leds - 2; count >= 0; count--)
delete_gpio_led(&priv->leds[count]);
return ERR_PTR(-ENODEV);
}

static const struct of_device_id of_gpio_leds_match[] = {
{ .compatible = "gpio-leds", },
{},
};
#else /* CONFIG_OF_GPIO */
static struct gpio_leds_priv *gpio_leds_create_of(struct platform_device *pdev)
{
return ERR_PTR(-ENODEV);
}
#endif /* CONFIG_OF_GPIO */

static int gpio_led_probe(struct platform_device *pdev)
{
struct gpio_led_platform_data *pdata = pdev->dev.platform_data;
//gpio_led_probe函数中，获取平台信息platform_data，作为参数传给函数creat_gpio_led的template参数，最后通过该参数付给了led_dat->cdev.name。
struct gpio_leds_priv *priv;
struct pinctrl *pinctrl;
int i, ret = 0;

pinctrl = devm_pinctrl_get_select_default(&pdev->dev);
if (IS_ERR(pinctrl))
dev_warn(&pdev->dev,
"pins are not configured from the driver\n");

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],//依次在/sys/class/leds目录下创建所有led设备。
     &priv->leds[i],
     &pdev->dev, pdata->gpio_blink_set);
if (ret < 0) {
/* On failure: unwind the led creations */
for (i = i - 1; i >= 0; i--)
delete_gpio_led(&priv->leds[i]);
return ret;
}
}
} else {
priv = gpio_leds_create_of(pdev);
if (IS_ERR(priv))
return PTR_ERR(priv);
}

platform_set_drvdata(pdev, priv);

return 0;
}

static int gpio_led_remove(struct platform_device *pdev)
{
struct gpio_leds_priv *priv = platform_get_drvdata(pdev);
int i;

for (i = 0; i < priv->num_leds; i++)
delete_gpio_led(&priv->leds[i]);

platform_set_drvdata(pdev, NULL);

return 0;
}

static struct platform_driver gpio_led_driver = {
.probe = gpio_led_probe,
.remove = gpio_led_remove,
.driver = {
.name = "leds-gpio",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(of_gpio_leds_match),
},
};

module_platform_driver(gpio_led_driver);

MODULE_AUTHOR("Raphael Assenat , Trent Piepho ");
MODULE_DESCRIPTION("GPIO LED driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-gpio");