需求：

        利用GPIO子系统与定时器实现LED1~3每隔1s翻转一次

实现过程：

        1.利用GPIO子系统实现驱动LED硬件工作，需要利用核心层提供的API接口函数

        2.gpio控制器结点已经在设备树文件中编写好，我们只需要在自己编写的led设备结点中正确引用

        3.根据源码目录下Documentation/devicetree/bindings/gpio下的gpio.txt可查阅纯净版本的帮助信息

        获得如下帮助信息

gpio1: gpio1 {
    gpio-controller;
    #gpio-cells = <2>;
};
[...]

data-gpios = <&gpio1 12 0>,
         <&gpio1 13 0>,
         <&gpio1 14 0>,
         <&gpio1 15 0>;     

        4.得知引用gpio结点需要的u32参数个数和写法

        5.在源码目录下/arch/arm/boot/dts/stm32mp157a-fsmp1a.dts添加自己的led结点内容：myleds 

/dts-v1/;
#include "stm32mp157.dtsi"
#include "stm32mp15xa.dtsi"
#include "stm32mp15-pinctrl.dtsi"
#include "stm32mp15xxac-pinctrl.dtsi"
#include "stm32mp15xx-fsmp1x.dtsi" 
/ {model = "HQYJ STM32MP157 FSMP1A Discovery Board";compatible = "st,stm32mp157a-dk1", "st,stm32mp157";aliases {serial0 = &uart4;serial5 = &usart3;};chosen {stdout-path = "serial0:115200n8";};reserved-memory {gpu_reserved: gpu@d4000000 {reg = <0xd4000000 0x4000000>;no-map;};optee_memory: optee@0xde000000 {reg = <0xde000000 0x02000000>;no-map;};};mynode@0x12345678{astring="hello 21091";uint  =<0xaabbccdd 0x11223344>;binarry=[00 0c 29 7b f9 be];mixed ="hello",[11 22],<0x12345678>;};leds{core-leds{led1=<&gpioz 5 0>;led2=<&gpioz 6 0>;led3=<&gpioz 7 0>;};extend-leds{led1=<&gpioe 10 0>;led2=<&gpiof 10 0>;led3=<&gpioe 8 0>;};};	keyirq{key_gpio = <&gpiof 9 0>,<&gpiof 7 0>,<&gpiof 8 0>;interrupt-parent = <&gpiof>;  //指定中断的父节点interrupts=<9 0>,<7 0>,<8 0>;   //9中断的index号，0中断的触发方式（默认）};myplatform{compatible = "hqyj,hello2";led1 = <&gpioe 10 0>;interrupt-parent = <&gpiof>;  //指定中断的父节点interrupts=<9 0>;	};mynode@0x12345678{compatible = "hqyj,mynode";astring = "hello 22101";uint = <0xaabbccdd 0x11223344>;binarry = [00 0c 29 7b f9 be];mixed = "hello",[11 22],<0x12345678>;};myleds{led1=<&gpioe 10 0>;led2=<&gpiof 10 0>;led3=<&gpioe 8 0>;};
};&i2c1{pinctrl-names = "default", "sleep";pinctrl-0 = <&i2c1_pins_b>;pinctrl-1 = <&i2c1_sleep_pins_b>;i2c-scl-rising-time-ns = <100>;i2c-scl-falling-time-ns = <7>;status = "okay";/delete-property/dmas;/delete-property/dma-names;si7006@40{compatible = "sl,si7006";reg = <0x40>;};
};
&spi4{pinctrl-names = "default", "sleep";pinctrl-0 = <&spi4_pins_b>;pinctrl-1 = <&spi4_sleep_pins_b>;     cs-gpios = <&gpioe 11 0>; //片选status = "okay";m74hc595@0{compatible = "hqyj,m74hc595";reg = <0>;spi-max-frequency = <10000000>; //10Mhz};
};

        6.利用核心层的API接口函数编写驱动模块代码：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/poll.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/timer.h>struct device_node* dnode;
struct timer_list timer;
//定义变量用于接收gpio编号
int gpiono1;
int gpiono2;
int gpiono3;void timer_handler(struct timer_list *timer)
{//设置gpio编号对应的管脚输出值gpio_set_value(gpiono1,!gpio_get_value(gpiono1));gpio_set_value(gpiono2,!gpio_get_value(gpiono2));gpio_set_value(gpiono3,!gpio_get_value(gpiono3));mod_timer(timer,jiffies+HZ);printk("toggle\n");
}// 入口函数
static int __init mycdev_init(void)
{//解析设备树结点获取节点信息结构体dnode=of_find_node_by_name(NULL,"myleds");if(NULL == dnode){printk("解析设备树结点失败\n");return -EIO;}printk("解析设备树结点成功\n");//解析结点信息结构体内容获得gpio编号gpiono1~3gpiono1 = of_get_named_gpio(dnode,"led1",0);if(gpiono1 < 0){printk("解析gpio编号失败\n");return -EIO;}printk("解析gpio编号成功\n");gpiono2 = of_get_named_gpio(dnode,"led2",0);if(gpiono2 < 0){printk("解析gpio编号失败\n");return -EIO;}printk("解析gpio编号成功\n");gpiono3 = of_get_named_gpio(dnode,"led3",0);if(gpiono3 < 0){printk("解析gpio编号失败\n");return -EIO;}printk("解析gpio编号成功\n");//向内核申请使用gpio编号并设置为输出模式与默认低电平gpio_request(gpiono1,NULL);gpio_direction_output(gpiono1,0);gpio_request(gpiono2,NULL);gpio_direction_output(gpiono2,0);gpio_request(gpiono3,NULL);gpio_direction_output(gpiono3,0);//利用定时器延时timer.expires=jiffies+HZ;timer_setup(&timer,timer_handler,0);add_timer(&timer);return 0;
}
// 出口函数
static void __exit mycdev_exit(void)
{//销毁定时器del_timer(&timer);//将注册的gpio编号从内核中注销gpio_free(gpiono3);gpio_free(gpiono2);gpio_free(gpiono1); 
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

实现结果：