40.linux自带LED驱动
LED 灯这样非常基础的设备驱动， Linux 内核已经集成了
Linux 内核的 LED 灯驱动采用 platform 框架，因此我们只需要按照要求在设备树文件中添加相应的 LED 节点即可
在linux内核下打开图形配置界面
c
make menuconfig
-> Device Drivers
-> LED Support (NEW_LEDS [=y])
->LED Support for GPIO connected LEDs输入'y'就将其编译进 Linux 内核。
在配置界面也可以通过配置项直接操作该该配置项
输入 / CONFIG_LEDS_GPIO
会罗列出选项
输入数字 1 2 3 等会跳转到相应的配置项。
配置完成后保存，会自动生成.config配置文件
打开.config 文件，会找到"CONFIG_LEDS_GPIO=y"这一行
重新编译 Linux 内核，然后使用新编译出来的 zImage 镜像启动开发板。
c
obj-$(CONFIG_LEDS_GPIO) += leds-gpio.o
c
obj-y += leds-gpio.o内核自带的LED驱动如下，地址在driver/leds/leds-goio.c
c
/*
* LEDs driver for GPIOs
*
* Copyright (C) 2007 8D Technologies inc.
* Raphael Assenat <raph@8d.com>
* Copyright (C) 2008 Freescale Semiconductor, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
struct gpio_led_data {
struct led_classdev cdev; // 内嵌的 led_classdev 结构，用于与 LED 子系统交互
struct gpio_desc *gpiod; // GPIO 描述符，现代内核用于代表一个 GPIO 引脚
struct work_struct work; // 工作队列，用于可以休眠的 GPIO 操作
u8 new_level; // 存储将要设置的新电平 (0 或 1)
u8 can_sleep; // 标志位，表示操作此 GPIO 是否可能引起休眠
u8 blinking; // 标志位，表示是否正在使用硬件闪烁
int (*platform_gpio_blink_set)(struct gpio_desc *desc, int state,
unsigned long *delay_on, unsigned long *delay_off); // 函数指针，指向平台相关的硬件闪烁实现
};
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) {
led_dat->platform_gpio_blink_set(led_dat->gpiod,
led_dat->new_level, NULL, NULL);
led_dat->blinking = 0;
} else
gpiod_set_value_cansleep(led_dat->gpiod, 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)
level = 0;
else
level = 1;
/* 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) {
led_dat->new_level = level;
schedule_work(&led_dat->work);
} else {
if (led_dat->blinking) {
led_dat->platform_gpio_blink_set(led_dat->gpiod, level,
NULL, NULL);
led_dat->blinking = 0;
} else
gpiod_set_value(led_dat->gpiod, level);
}
}
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->gpiod, 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)(struct gpio_desc *, int, unsigned long *,
unsigned long *))
{
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 = 0;
/* 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;
}
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);
if (IS_ERR(led_dat->gpiod))
return PTR_ERR(led_dat->gpiod);
}
led_dat->cdev.name = template->name;
led_dat->cdev.default_trigger = template->default_trigger;
led_dat->can_sleep = gpiod_cansleep(led_dat->gpiod);
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 = !!gpiod_get_value_cansleep(led_dat->gpiod);
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 = gpiod_direction_output(led_dat->gpiod, state);
if (ret < 0)
return ret;
INIT_WORK(&led_dat->work, gpio_led_work);
return led_classdev_register(parent, &led_dat->cdev);
}
static void delete_gpio_led(struct gpio_led_data *led)
{
led_classdev_unregister(&led->cdev);
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);
}
/* // 设备树中的片段
leds {
compatible = "gpio-leds"; // 驱动通过这个属性匹配到本节点
// ↓↓↓ gpio_leds_create 函数主要处理下面的子节点 ↓↓↓
power_led { // 第一个子节点 (child 1)
label = "green:power";
gpios = <&gpio3 4 GPIO_ACTIVE_HIGH>;
default-state = "on";
};
storage_led { // 第二个子节点 (child 2)
label = "yellow:storage";
gpios = <&gpio3 5 GPIO_ACTIVE_HIGH>;
linux,default-trigger = "disk-activity";
};
}; */
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;
struct device_node *np;
count = device_get_child_node_count(dev); //检查 leds 节点下有多少个子节点。在上面的例子中，count 会得到 2（power_led 和 storage_led）。
if (!count)
return ERR_PTR(-ENODEV);
priv = devm_kzalloc(dev, sizeof_gpio_leds_priv(count), GFP_KERNEL); //内存分配就为父结构体和它包含的所有子结构体数组分配了连续的空间，非常高效。
if (!priv)
return ERR_PTR(-ENOMEM);
device_for_each_child_node(dev, child) { //遍历并解析每个子节点先是 power_led，然后是 storage_led
struct gpio_led led = {};
const char *state = NULL;
led.gpiod = devm_get_gpiod_from_child(dev, NULL, child); //解析子节点中的 gpios 属性,<&gpio3 4 GPIO_ACTIVE_HIGH> 并返回一个 gpio_desc（GPIO 描述符）
if (IS_ERR(led.gpiod)) {
fwnode_handle_put(child);
ret = PTR_ERR(led.gpiod);
goto err;
}
np = of_node(child);
if (fwnode_property_present(child, "label")) { //获取 LED 名称 (label)
fwnode_property_read_string(child, "label", &led.name); //作为led.name的设备名字
} else {
if (IS_ENABLED(CONFIG_OF) && !led.name && np) //如果 label 不存在，它会尝试使用节点名（如 "power_led"）作为备选。
led.name = np->name;
if (!led.name)
return ERR_PTR(-EINVAL);
}
//读取其他信息
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;
//上面的工作都是将一个子节点的所有属性都解析完毕并存入临时的 led 结构体后，就调用 create_gpio_led 函数去完成实际的创建工作。
ret = create_gpio_led(&led, &priv->leds[priv->num_leds++],
dev, NULL);
if (ret < 0) {
fwnode_handle_put(child);
goto err;
}
}
return priv;
//错误处理
err:
for (count = priv->num_leds - 2; count >= 0; count--)
delete_gpio_led(&priv->leds[count]);
return ERR_PTR(ret);
}
static const struct of_device_id of_gpio_leds_match[] = {
{ .compatible = "gpio-leds", },
{},
};
MODULE_DEVICE_TABLE(of, of_gpio_leds_match);
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) { //兼容有无设备树平台
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, 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 { //有设备树时
priv = gpio_leds_create(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]);
return 0;
}
static struct platform_driver gpio_led_driver = {
.probe = gpio_led_probe,
.remove = gpio_led_remove,
.driver = {
.name = "leds-gpio",
.of_match_table = of_gpio_leds_match,
},
};
module_platform_driver(gpio_led_driver);
MODULE_AUTHOR("Raphael Assenat <raph@8d.com>, Trent Piepho <tpiepho@freescale.com>");
MODULE_DESCRIPTION("GPIO LED driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-gpio");其中
c
module_platform_driver(gpio_led_driver);是一个宏定义
c
module_platform_driver(gpio_led_driver);
#define module_platform_driver(__platform_driver) \
module_driver(__platform_driver, platform_driver_register, platform_driver_unregister)
#define module_driver(__driver, __register, __unregister, ...) \
static int __init __driver##_init(void) \
{ \
return __register(&(__driver) , ##__VA_ARGS__); \
} \
module_init(__driver##_init); \
static void __exit __driver##_exit(void) \
{ \
__unregister(&(__driver) , ##__VA_ARGS__); \
} \
module_exit(__driver##_exit);展开后 , ##__VA_ARGS__可变参数,没有
##为c语言的拼接运算符 a##b -》 ab
最后展开为：
c
#define module_platform_driver(gpio_led_driver)
static int __init gpio_led_driver_init(void)
{
return module_platform_driver(&gpio_led_driver);
}
module_init(gpio_led_driver_init);
static void __exit gpio_led_driver_exit(void)
{
platform_driver_unregister(&gpio_led_driver );
}
module_exit(__driver##_exit);也就是我们之前写的moudule框架
我们来学习一下:
1.使用platform驱动注册了led-gpio，一个入口是probe函数，出口是remove函数
gpio_led_probe（） 匹配成功后执行该函数
-》create_gpio_led
柔性数组成员
内核自带的LED驱动使用
1.首先将驱动编译进内核里面
2.根据绑定文档（Documentation/devicetree/bindings/leds/leds-gpio.txt）在设备树里面添加对应的节点信息。
没有设备就需要39节注册device
使用设备数需要按照文档进行添加这样的节点
c
/
leds {
compatible = "gpio-leds";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_gpio_leds>;
led1{
label = "sys-led";
gpios = <&gpio1 3 GPIO_ACTIVE_LOW>;
linux,default-trigger = "heartbeat";
default-state = "on";
};
};
&iomuxcu{
...
pinctrl_gpio_leds: gpio-leds {
fsl,pins = <
MX6UL_PAD_GPIO1_IO03__GPIO1_IO03 0x17059
>;
};
...
};当然不止可以添加一个led，也可以添加多个led
c
leds {
compatible = "gpio-leds";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_gpio_leds
&pinctrl_beep
>;
led1{
label = "sys-led";
gpios = <&gpio1 3 GPIO_ACTIVE_LOW>;
//linux,default-trigger = "heartbeat"; 可以设置为心跳
default-state = "on";
};
...
&iomuxcu{
...
pinctrl_gpio_leds: gpio-leds {
fsl,pins = <
MX6UL_PAD_GPIO1_IO03__GPIO1_IO03 0x17059
>;
};
pinctrl_beep:beep {
fsl,pin = <
MX6ULL_PAD_SNVS_TAMPER1__GPIO5_IO01 0x10B0
>;
};
...
};只需要compatible属性值为gpio-leds，那么linux自带的LED驱动就会匹配上，然后自动执行驱动内容。
在用户空间使用led驱动
当然还可以使用命令来对linxu的led驱动做出设置
在用户空间使用led驱动
c
/sys/devices/platform/leds/leds/sys-led # cat trigger
[none] rc-feedback nand-disk mmc0 mmc1 timer oneshot heartbeat backlight gpio
/sys/devices/platform/leds/leds/sys-led # echo heartbeat > trigger
/sys/devices/platform/leds/leds/sys-led # cat trigger
none rc-feedback nand-disk mmc0 mmc1 timer oneshot [heartbeat] backlight gpioheartbeat\]表示选择了心跳模式 ```c echo heartbeat > trigger ``` 修改了trigger模式为心跳。 ```c echo none > trigger ``` 关闭LED ```c echo 1 > brightness ``` ### 在用户空间使用led驱动 当然还可以使用命令来对linxu的led驱动做出设置 在用户空间使用led驱动 ```c /sys/devices/platform/leds/leds/sys-led # cat trigger [none] rc-feedback nand-disk mmc0 mmc1 timer oneshot heartbeat backlight gpio /sys/devices/platform/leds/leds/sys-led # echo heartbeat > trigger /sys/devices/platform/leds/leds/sys-led # cat trigger none rc-feedback nand-disk mmc0 mmc1 timer oneshot [heartbeat] backlight gpio ``` \[heartbeat\]表示选择了心跳模式 ```c echo heartbeat > trigger ``` 修改了trigger模式为心跳。 ```c echo none > trigger ``` 关闭LED ```c echo 1 > brightness ``` 设置为常亮（需要trigger为none）