[系统运维]Linux字符设备驱动详解六（设备树实现RGB灯驱动）

系列文章目录

Linux字符设备驱动详解
Linux字符设备驱动详解二（使用设备驱动模型）
Linux字符设备驱动详解三（使用class）
Linux字符设备驱动详解四（使用自属的xbus驱动总线）
Linux字符设备驱动详解五（使用platform虚拟平台总线）

前言

本文主要来自正点原子、野火Linux教程及本人理解，若有侵权请及时联系本人删除。

正文

一、DTS设备树基本语法从上到下

背景

硬件设备中种类逐年递增，板级platform平台设备文件越来越多，这么多的设备如果都要自己写platform_device.c文件，那将需要跟每个外设的寄存器打交道，并且需要很多的platform_device.c文件

设备树简介

• DTS(device tree source)：设备树源文件，ASCII 格式
• DTC(device tree compiler)：设备树编译工具
• DTB(device tree blob)：二进制设备树

设备树使用

uboot负责加载到内存，内核解析使用

设备树源文件

ebf-buster-linux/arch/arm/boot/dts/imx6ull-seeed-npi.dts

二进制设备树

pc：ebf-buster-linux/arch/arm/boot/dts/imx6ull-seeed-npi.dtb
开发板：/boot/dtbs/4.19.71-imx-r1/imx6ull-seeed-npi.dtb

设备树编译工具

内核编译

//进行内核配置
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- npi_v7_defconfig
//编译dts
make ARCH=arm -j4 CROSS_COMPILE=arm-linux-gnueabihf- dtbs

手工编译

./scripts/dtc/dtc -I dts -O dtb -o xxx.dtb arch/arm/boot/dts/xxx.dts // 编译 dts 为 dtb
./scripts/dtc/dtc -I dtb -O dts -o xxx.dts arch/arm/boot/dts/xxx.dtb // 反编译 dtb 为 dts

• -I：指定输入格式
• -O：指定输出格式
• -o：指定输出文件

设备树框架

• 从上到下
  • 头文件
  • 主体
  • 子节点追加内容
• 从外到内
  • 属性
  • 其他子节点
    • 属性
    • 其他子节点
    • …

头文件：

#include <dt-bindings/input/input.h>
#include "imx6ull.dtsi"

主体：

/ {  
    model = "Seeed i.MX6 ULL NPi Board";
    compatible = "fsl,imx6ull-14x14-evk", "fsl,imx6ull";

    aliases {
            pwm0 = &pwm1;
            pwm1 = &pwm2;
            pwm2 = &pwm3;
            pwm3 = &pwm4;
    };
    chosen {
            stdout-path = &uart1;
    };

    memory {
            reg = <0x80000000 0x20000000>;
    };

    reserved-memory {
            #address-cells = <1>;
            #size-cells = <1>;
            ranges;

            linux,cma {
                    compatible = "shared-dma-pool";
                    reusable;
                    size = <0x14000000>;
                    linux,cma-default;
            };
    };
    ...
};

• 多个根节点合并
• 根节点下包含多个子节点

子节点追加内容

&cpu0 {
    dc-supply = <&reg_gpio_dvfs>;
    clock-frequency = <800000000>;
};

&clks {
    assigned-clocks = <&clks IMX6UL_CLK_PLL4_AUDIO_DIV>;
    assigned-clock-rates = <786432000>;
};


&fec1 {
    pinctrl-names = "default";
    pinctrl-0 = <&pinctrl_enet1>;
    phy-mode = "rmii";
    phy-handle = <&ethphy0>;
    status = "okay";
};

节点命令

基本方法

node-name@unit-address{

属性1 = …

属性2 = …

属性3= …

子节点…

}

• node-name：指定节点的名称
• “unit-address”用于指定“单元地址”

节点标签

cpu0: cpu@0 {
    compatible = "arm,cortex-a7";
    device_type = "cpu";
    reg = <0>;
}

• cpu0：为节点名称器一个别名

别名子节点

    aliases {

二、DTS设备树基本语法从外到内

• 从上到下

  • 头文件
  • 主体
  • 子节点追加内容

• 从外到内

  • 属性
  • 其他子节点
    • 属性
    • 其他子节点
    • …

常见节点属性

compatible属性：
值类型：字符串

intc: interrupt-controller@a01000 {
    compatible = "arm,cortex-a7-gic";
    #interrupt-cells = <3>;
    interrupt-controller;
    reg = <0xa01000 0x1000>,
          <0xa02000 0x100>;
};

• arm：芯片厂商
• cortex-a7-gic：模块对应的驱动名字

model属性：
值类型：字符串

model = "embedfire i.MX6 ULL NPi Board";

• 准确描述当前板子型号信息

status属性：
值类型：字符串

reg属性：
值类型：一系列《地址、长度》对

ocrams: sram@900000 {
      compatible = "fsl,lpm-sram";
      reg = <0x900000 0x4000>;
    };

• 地址：外设寄存器组的起始地址
• 长度：外设寄存器组的字节长度

#address-cells和#size-cells属性：
值类型：u32

soc {
    #address-cells = <1>;
    #size-cells = <0>;
    compatible = "simple-bus";
    interrupt-parent = <&gpc>;
    ranges;
    ocrams: sram@900000 {
            compatible = "fsl,lpm-sram";
            reg = <0x900000>;
    };
};

• #address-cells :设置子节点中reg地址的数量
• #size-cells：设置子节点中reg地址的长度的数量

linux系统中查看设备树

ls /sys/firmware/devicetree/base

或者

ls /proc/device-tree

• 以目录的形式体现设备树结构

添加子节点

test_led{
	#address-cells = <1>;
	#size-cells = <1>;

	rgb_led_red@0x0209C000{
			compatible = "fire,rgb_led_red";
			reg = <0x0209C000 0x00000020>;
			status = "okay";
	};
};

三、获取DTS属性信息

• 查属性所在的节点
• 查节点的属性值

节点表示

struct device_node {
    const char *name;  //节点名
    const char *type;  //设备类型
    phandle phandle;
    const char *full_name; //完整名字
    struct fwnode_handle fwnode;
   
    struct  property *properties; //属性
    struct  property *deadprops; 
    struct  device_node *parent; //父节点
    struct  device_node *child;  //子节点
    struct  device_node *sibling;
#if defined(CONFIG_OF_KOBJ)
    struct  kobject kobj;
#endif
    unsigned long _flags;
    void    *data;
#if defined(CONFIG_SPARC)
    const char *path_component_name;
    unsigned int unique_id;
    struct of_irq_controller *irq_trans;
#endif
};

查节点

• 路径/类型/名字/compatible

of_find_node_by_path()函数，根据路径找到节点

struct device_node *of_find_node_by_path(struct device_node *from,const char *path);

参数：

• from：开始查找的节点，NULL表示从根节点开始查找
• path：查找的节点名

返回值：
成功：device_node表示的节点
失败：NULL

of_find_node_by_type()函数，根据“device_type“属性来查找节点，不建议使用

struct device_node *of_find_node_by_type(struct device_node *from, const char *type);

of_find_node_by_name()函数，根据"name"属性来查找节点，不建议使用

struct device_node *of_find_node_by_name(struct device_node *from,const char *name);

of_find_compatible_node()函数

struct device_node *of_find_compatible_node(struct device_node *from,const char *type, const char *compat);

参数：

• from：开始查找的节点，NULL表示从根节点开始查找
• type：指定 device_type 属性值
• compat：指定 compatible 属性值

返回值：
成功：device_node表示的节点
失败：NULL

查节点的属性值

struct property {
    char    *name;  	//属性名
    int     length;     //属性长度
    void    *value; 	//属性值
    struct property *next; //下一个属性
#if defined(CONFIG_OF_DYNAMIC) || defined(CONFIG_SPARC)
    unsigned long _flags;
#endif
#if defined(CONFIG_OF_PROMTREE)
    unsigned int unique_id;
#endif
#if defined(CONFIG_OF_KOBJ)
    struct bin_attribute attr;
#endif
};

of_find_property()函数

• 节点+属性名

查找节点中的属性

struct property *of_find_property(const struct device_node *np,const char *name,int *lenp);

参数：

• np：device_node表示的节点
• name：查找的属性名字
• lenp：属性值的字节数

返回值：
成功：property表示的属性
失败：NULL

案例：

test_property {
test_name = “hello”;
};

name：“hello”
lenp = 6
of_property_read_u32()函数，读取一个32位无符号整数

static inline int of_property_read_u32(const struct device_node *np,const char *propname,

参数：

• np：device_node表示的节点
• propname：查找的属性名字
• out_value：属性值的整数值

返回值：
成功：0
失败：负值
of_property_read_u32_array()函数，读取32位无符号整数数组

int of_property_read_u32_array(const struct device_node *np,const char *propname,u32 *out_values,size_t sz)

• np：device_node表示的节点
• name：查找的属性名字
• out_value：读取到的数组值
• sz ：要读取的数组元素数量
  of_property_read_string()函数，读字符串

int of_property_read_string(struct device_node *np,const char *propname,const char **out_string)

参数：

• np：device_node表示的节点
• proname：查找的属性名字
• out_string：读取到的字符串值

返回值：
成功：0
失败：负值

代码示例

以野火设备驱动模型代码为例
get_dts_info.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <asm/mach/map.h>
#include <asm/io.h>

#include <linux/of.h>
#include <linux/of_address.h>


#define DEV_NAME            "get_dts_info"
#define DEV_CNT                 (1)
//定义字符设备的设备号
static dev_t led_devno;
//定义字符设备结构体chr_dev
static struct cdev led_chr_dev;
//创建类
struct class *led_chrdev_class;


struct device_node	*led_device_node; //led的设备树节点
struct device_node  *rgb_led_red_device_node; //rgb_led_red 红灯节点
struct property     *rgb_led_red_property;    //定义属性结构体指针
int size = 0 ;
unsigned int out_values[18];  //保存读取得到的REG 属性值

/*.open 函数*/
static int led_chr_dev_open(struct inode *inode, struct file *filp)
{
    int error_status = -1;

    printk("\n open form device \n");

    /*获取DTS属性信息*/
    led_device_node = of_find_node_by_path("/test_led");
    if(led_device_node == NULL)
    {
        printk(KERN_ALERT "\n get led_device_node failed ! \n");
        return -1;
    }
    /*根据 led_device_node 设备节点结构体输出节点的基本信息*/
    printk(KERN_ALERT "name: %s",led_device_node->name); //输出节点名
    printk(KERN_ALERT "child name: %s",led_device_node->child->name);  //输出子节点的节点名


    /*获取 rgb_led_red_device_node 的子节点*/ 
    rgb_led_red_device_node = of_get_next_child(led_device_node,NULL); 
    if(rgb_led_red_device_node == NULL)
    {
        printk(KERN_ALERT "\n get rgb_led_red_device_node failed ! \n");
        return -1;
    }
    printk(KERN_ALERT "name: %s",rgb_led_red_device_node->name); //输出节点名
    printk(KERN_ALERT "parent name: %s",rgb_led_red_device_node->parent->name);  //输出父节点的节点名


    /*获取 rgb_led_red_device_node 节点  的"compatible" 属性 */ 
    rgb_led_red_property = of_find_property(rgb_led_red_device_node,"compatible",&size);
    if(rgb_led_red_property == NULL)
    {
        printk(KERN_ALERT "\n get rgb_led_red_property failed ! \n");
        return -1;
    }
    printk(KERN_ALERT "size = : %d",size);                      //实际读取得到的长度
    printk(KERN_ALERT "name: %s",rgb_led_red_property->name);   //输出属性名
    printk(KERN_ALERT "length: %d",rgb_led_red_property->length);        //输出属性长度
    printk(KERN_ALERT "value : %s",(char*)rgb_led_red_property->value);  //属性值


    /*获取 reg 地址属性*/
    error_status = of_property_read_u32_array(rgb_led_red_device_node,"reg",out_values, 2);
    if(error_status != 0)
    {
        printk(KERN_ALERT "\n get out_values failed ! \n");
        return -1;
    }
    printk(KERN_ALERT"0x%08X ", out_values[0]);
    printk(KERN_ALERT"0x%08X ", out_values[1]);

    return 0;
}

/*.release 函数*/
static int led_chr_dev_release(struct inode *inode, struct file *filp)
{
    printk("\nrelease\n");
    return 0;
}


/*字符设备操作函数集*/
static struct file_operations  led_chr_dev_fops = 
{
    .owner = THIS_MODULE,
    .open = led_chr_dev_open,
    .release = led_chr_dev_release,
};



/*
*驱动初始化函数
*/
static int __init led_chrdev_init(void)
{
    int ret = 0;
    printk("led chrdev init\n");
    //第一步
    //采用动态分配的方式，获取设备编号，次设备号为0，
    //设备名称为EmbedCharDev，可通过命令cat  /proc/devices查看
    //DEV_CNT为1，当前只申请一个设备编号
    ret = alloc_chrdev_region(&led_devno, 0, DEV_CNT, DEV_NAME);
    if(ret < 0){
        printk("fail to alloc led_devno\n");
        goto alloc_err;
    }

    led_chrdev_class = class_create(THIS_MODULE, "led_chrdev");
    //第二步
    //关联字符设备结构体cdev与文件操作结构体file_operations
    cdev_init(&led_chr_dev, &led_chr_dev_fops);
    //第三步
    //添加设备至cdev_map散列表中
    ret = cdev_add(&led_chr_dev, led_devno, DEV_CNT);
    if(ret < 0)
    {
        printk("fail to add cdev\n");
        goto add_err;
    }

    //创建设备
    device_create(led_chrdev_class, NULL, led_devno, NULL,
			      DEV_NAME);
    return 0;

add_err:
    //添加设备失败时，需要注销设备号
    unregister_chrdev_region(led_devno, DEV_CNT);
alloc_err:
    return ret;
}





/*
*驱动注销函数
*/

static void __exit led_chrdev_exit(void)
{
    printk("chrdev exit\n");
   
    device_destroy(led_chrdev_class, led_devno);   //清除设备
    cdev_del(&led_chr_dev);                        //清除设备号
    unregister_chrdev_region(led_devno, DEV_CNT);  //取消注册字符设备
    class_destroy(led_chrdev_class);               //清除类
}

module_init(led_chrdev_init);
module_exit(led_chrdev_exit);

MODULE_LICENSE("GPL");

四、 设备树实现RGB灯驱动

设备树添加节点信息

RGB灯的相关寄存器

/*
*CCM_CCGR1                         0x020C406C
*IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO04  0x020E006C
*IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO04  0x020E02F8
*GPIO1_GD                          0x0209C000
*GPIO1_GDIR                        0x0209C004
*/


/*
*CCM_CCGR3                         0x020C4074
*IOMUXC_SW_MUX_CTL_PAD_CSI_HSYNC   0x020E01E0
*IOMUXC_SW_PAD_CTL_PAD_CSI_HSYNC   0x020E046C
*GPIO4_GD                          0x020A8000
*GPIO4_GDIR                        0x020A8004
*/


/*
*CCM_CCGR3                         0x020C4074
*IOMUXC_SW_MUX_CTL_PAD_CSI_VSYNC   0x020E01DC
*IOMUXC_SW_PAD_CTL_PAD_CSI_VSYNC   0x020E0468
*GPIO4_GD                          0x020A8000
*GPIO4_GDIR                        0x020A8004
*/
	/*添加led节点*/
	rgb_led{
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "fire,rgb_led";

		/*红灯节点*/
		ranges;
		rgb_led_red@0x020C406C{
			reg = <0x020C406C 0x00000004
			       0x020E006C 0x00000004
			       0x020E02F8 0x00000004
				   0x0209C000 0x00000004
			       0x0209C004 0x00000004>;
			status = "okay";
		};

		/*绿灯节点*/
		rgb_led_green@0x020C4074{
			reg = <0x020C4074 0x00000004
			       0x020E01E0 0x00000004
			       0x020E046C 0x00000004
				   0x020A8000 0x00000004
			       0x020A8004 0x00000004>;
			status = "okay";
		};

		/*蓝灯节点*/
		rgb_led_blue@0x020C4074{
			reg = <0x020C4074 0x00000004
			       0x020E01DC 0x00000004
			       0x020E0468 0x00000004
				   0x020A8000 0x00000004
			       0x020A8004 0x00000004>;
			status = "okay";
		};
	};

reg属性内存映射

of_iomap()函数将reg属性值的物理地址转化为虚拟地址

void __iomem *of_iomap(struct device_node *np,
int index)

参数：

• np：device_node表示的节点
• index：通常情况下reg属性包含多段，index 用于指定映射那一段，标号从0开始。

代码示例

以野火设备驱动模型代码为例
dts_led.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <asm/mach/map.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_gpio.h>
#include <asm/io.h>
#include <linux/device.h>

#include <linux/platform_device.h>

/*------------------字符设备内容----------------------*/
#define DEV_NAME "rgb_led"
#define DEV_CNT (1)

/*定义 led 资源结构体，保存获取得到的节点信息以及转换后的虚拟寄存器地址*/
struct led_resource
{
	struct device_node *device_node; //rgb_led_red的设备树节点
	void __iomem *virtual_CCM_CCGR;
	void __iomem *virtual_IOMUXC_SW_MUX_CTL_PAD;
	void __iomem *virtual_IOMUXC_SW_PAD_CTL_PAD;
	void __iomem *virtual_DR;
	void __iomem *virtual_GDIR;
};

static dev_t led_devno;					 //定义字符设备的设备号
static struct cdev led_chr_dev;			 //定义字符设备结构体chr_dev
struct class *class_led;				 //保存创建的类
struct device *device;					 // 保存创建的设备
struct device_node *rgb_led_device_node; //rgb_led的设备树节点结构体

/*定义 R G B 三个灯的led_resource 结构体，保存获取得到的节点信息*/
struct led_resource led_red;
struct led_resource led_green;
struct led_resource led_blue;

/*字符设备操作函数集，open函数*/
static int led_chr_dev_open(struct inode *inode, struct file *filp)
{
	printk("\n open form driver \n");
	return 0;
}

/*字符设备操作函数集，write函数*/
static ssize_t led_chr_dev_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{

	int ret,error;
	unsigned int register_data = 0; //暂存读取得到的寄存器数据
	unsigned char receive_data[10]; //用于保存接收到的数据
	unsigned int write_data; //用于保存接收到的数据

	if(cnt>10)
			cnt =10;

	error = copy_from_user(receive_data, buf, cnt);
	if (error < 0)
	{
		return -1;
	}

	ret = kstrtoint(receive_data, 16, &write_data);
	if (ret) {
		return -1;
        }

	/*设置 GPIO1_04 输出电平*/
	if (write_data & 0x04)
	{
		register_data = ioread32(led_red.virtual_DR);
		register_data &= ~(0x01 << 4);
		iowrite32(register_data, led_red.virtual_DR); // GPIO1_04引脚输出低电平，红灯亮
	}
	else
	{
		register_data = ioread32(led_red.virtual_DR);
		register_data |= (0x01 << 4);
		iowrite32(register_data, led_red.virtual_DR); // GPIO1_04引脚输出高电平，红灯灭
	}

	/*设置 GPIO4_20 输出电平*/
	if (write_data & 0x02)
	{
		register_data = ioread32(led_green.virtual_DR);
		register_data &= ~(0x01 << 20);
		iowrite32(register_data, led_green.virtual_DR); // GPIO4_20引脚输出低电平，绿灯亮
	}
	else
	{
		register_data = ioread32(led_green.virtual_DR);
		register_data |= (0x01 << 20);
		iowrite32(register_data, led_green.virtual_DR); // GPIO4_20引脚输出高电平，绿灯灭
	}

	/*设置 GPIO4_19 输出电平*/
	if (write_data & 0x01)
	{
		register_data = ioread32(led_blue.virtual_DR);
		register_data &= ~(0x01 << 19);
		iowrite32(register_data, led_blue.virtual_DR); //GPIO4_19引脚输出低电平，蓝灯亮
	}
	else
	{
		register_data = ioread32(led_blue.virtual_DR);
		register_data |= (0x01 << 19);
		iowrite32(register_data, led_blue.virtual_DR); //GPIO4_19引脚输出高电平，蓝灯灭
	}

	return cnt;
}

/*字符设备操作函数集*/
static struct file_operations led_chr_dev_fops =
	{
		.owner = THIS_MODULE,
		.open = led_chr_dev_open,
		.write = led_chr_dev_write,
};

/*----------------平台驱动函数集-----------------*/
static int led_probe(struct platform_device *pdv)
{

	int ret = -1; //保存错误状态码
	unsigned int register_data = 0;

	printk(KERN_ALERT "\t  match successed  \n");

	/*获取rgb_led的设备树节点*/
	rgb_led_device_node = of_find_node_by_path("/rgb_led");
	if (rgb_led_device_node == NULL)
	{
		printk(KERN_ERR "\t  get rgb_led failed!  \n");
		return -1;
	}

	/*获取rgb_led节点的红灯子节点*/
	led_red.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_red");
	if (led_red.device_node == NULL)
	{
		printk(KERN_ERR "\n get rgb_led_red_device_node failed ! \n");
		return -1;
	}


	/*获取 reg 属性并转化为虚拟地址*/
	led_red.virtual_CCM_CCGR = of_iomap(led_red.device_node, 0);
	led_red.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_red.device_node, 1);
	led_red.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_red.device_node, 2);
	led_red.virtual_DR = of_iomap(led_red.device_node, 3);
	led_red.virtual_GDIR = of_iomap(led_red.device_node, 4);

	/*初始化红灯*/
	register_data = ioread32(led_red.virtual_CCM_CCGR);
	register_data |= (0x03 << 26);
	iowrite32(register_data, led_red.virtual_CCM_CCGR); //开启时钟

	register_data = ioread32(led_red.virtual_IOMUXC_SW_MUX_CTL_PAD);
	register_data &= ~(0xf << 0);
	register_data |= (0x05 << 0);
	iowrite32(register_data, led_red.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能

	register_data = ioread32(led_red.virtual_IOMUXC_SW_PAD_CTL_PAD);
	register_data = (0x10B0);
	iowrite32(register_data, led_red.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性

	register_data = ioread32(led_red.virtual_GDIR);
	register_data |= (0x01 << 4);
	iowrite32(register_data, led_red.virtual_GDIR); //设置GPIO1_04 为输出模式

	register_data = ioread32(led_red.virtual_DR);
	register_data |= (0x01 << 4);
	iowrite32(register_data, led_red.virtual_DR); //设置 GPIO1_04 默认输出高电平






	/*获取rgb_led节点的绿灯子节点*/
	led_green.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_green");
	if (led_green.device_node == NULL)
	{
		printk(KERN_ERR "\n get rgb_led_green_device_node failed ! \n");
		return -1;
	}

	/*获取 reg 属性并转化为虚拟地址*/
	led_green.virtual_CCM_CCGR = of_iomap(led_green.device_node, 0);
	led_green.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_green.device_node, 1);
	led_green.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_green.device_node, 2);
	led_green.virtual_DR = of_iomap(led_green.device_node, 3);
	led_green.virtual_GDIR = of_iomap(led_green.device_node, 4);

	/*初始化绿灯*/
	register_data = ioread32(led_green.virtual_CCM_CCGR);
	register_data |= (0x03 << 12);
	iowrite32(register_data, led_green.virtual_CCM_CCGR); //开启时钟

	register_data = ioread32(led_green.virtual_IOMUXC_SW_MUX_CTL_PAD);
	register_data &= ~(0xf << 0);
	register_data |= (0x05 << 0);
	iowrite32(register_data, led_green.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能

	register_data = ioread32(led_green.virtual_IOMUXC_SW_PAD_CTL_PAD);
	register_data = (0x10B0);
	iowrite32(register_data, led_green.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性

	register_data = ioread32(led_green.virtual_GDIR);
	register_data |= (0x01 << 20);
	iowrite32(register_data, led_green.virtual_GDIR); //设置GPIO4_IO20 为输出模式

	register_data = ioread32(led_green.virtual_DR);
	register_data |= (0x01 << 20);
	iowrite32(register_data, led_green.virtual_DR); //设置 GPIO4_IO20 默认输出高电平






	/*获取rgb_led节点的蓝灯子节点*/
	led_blue.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_blue");
	if (led_blue.device_node == NULL)
	{
		printk(KERN_ERR "\n get rgb_led_blue_device_node failed ! \n");
		return -1;
	}

	/*获取 reg 属性并转化为虚拟地址*/
	led_blue.virtual_CCM_CCGR = of_iomap(led_blue.device_node, 0);
	led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_blue.device_node, 1);
	led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_blue.device_node, 2);
	led_blue.virtual_DR = of_iomap(led_blue.device_node, 3);
	led_blue.virtual_GDIR = of_iomap(led_blue.device_node, 4);

	/*初始化蓝灯*/
	register_data = ioread32(led_blue.virtual_CCM_CCGR);
	register_data |= (0x03 << 12);
	iowrite32(register_data, led_blue.virtual_CCM_CCGR); //开启时钟

	register_data = ioread32(led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD);
	register_data &= ~(0xf << 0);
	register_data |= (0x05 << 0);
	iowrite32(register_data, led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能

	register_data = ioread32(led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD);
	register_data = (0x10B0);
	iowrite32(register_data, led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性

	register_data = ioread32(led_blue.virtual_GDIR);
	register_data |= (0x01 << 19);
	iowrite32(register_data, led_blue.virtual_GDIR); //设置GPIO4_IO19 为输出模式

	register_data = ioread32(led_blue.virtual_DR);
	register_data |= (0x01 << 19);
	iowrite32(register_data, led_blue.virtual_DR); //设置 GPIO4_IO19 默认输出高电平








	/*---------------------注册 字符设备部分-----------------*/

	//第一步
	//采用动态分配的方式，获取设备编号，次设备号为0，
	//设备名称为rgb-leds，可通过命令cat  /proc/devices查看
	//DEV_CNT为1，当前只申请一个设备编号
	ret = alloc_chrdev_region(&led_devno, 0, DEV_CNT, DEV_NAME);
	if (ret < 0)
	{
		printk("fail to alloc led_devno\n");
		goto alloc_err;
	}
	//第二步
	//关联字符设备结构体cdev与文件操作结构体file_operations
	led_chr_dev.owner = THIS_MODULE;
	cdev_init(&led_chr_dev, &led_chr_dev_fops);
	//第三步
	//添加设备至cdev_map散列表中
	ret = cdev_add(&led_chr_dev, led_devno, DEV_CNT);
	if (ret < 0)
	{
		printk("fail to add cdev\n");
		goto add_err;
	}

	//第四步
	/*创建类 */
	class_led = class_create(THIS_MODULE, DEV_NAME);

	/*创建设备*/
	device = device_create(class_led, NULL, led_devno, NULL, DEV_NAME);

	return 0;

add_err:
	//添加设备失败时，需要注销设备号
	unregister_chrdev_region(led_devno, DEV_CNT);
	printk("\n error! \n");
alloc_err:

	return -1;
}

static const struct of_device_id rgb_led[] = {
	{.compatible = "fire,rgb_led"},
	{/* sentinel */}};

/*定义平台设备结构体*/
struct platform_driver led_platform_driver = {
	.probe = led_probe,
	.driver = {
		.name = "rgb-leds-platform",
		.owner = THIS_MODULE,
		.of_match_table = rgb_led,
	}};

/*
*驱动初始化函数
*/
static int __init led_platform_driver_init(void)
{
	int DriverState;
	DriverState = platform_driver_register(&led_platform_driver);
	printk(KERN_ALERT "\tDriverState is %d\n", DriverState);
	return 0;
}

/*
*驱动注销函数
*/
static void __exit led_platform_driver_exit(void)
{
	/*取消物理地址映射到虚拟地址*/
	iounmap(led_green.virtual_CCM_CCGR);
	iounmap(led_green.virtual_IOMUXC_SW_MUX_CTL_PAD);
	iounmap(led_green.virtual_IOMUXC_SW_PAD_CTL_PAD);
	iounmap(led_green.virtual_DR);
	iounmap(led_green.virtual_GDIR);

	iounmap(led_red.virtual_CCM_CCGR);
	iounmap(led_red.virtual_IOMUXC_SW_MUX_CTL_PAD);
	iounmap(led_red.virtual_IOMUXC_SW_PAD_CTL_PAD);
	iounmap(led_red.virtual_DR);
	iounmap(led_red.virtual_GDIR);

	iounmap(led_blue.virtual_CCM_CCGR);
	iounmap(led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD);
	iounmap(led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD);
	iounmap(led_blue.virtual_DR);
	iounmap(led_blue.virtual_GDIR);

	/*删除设备*/
	device_destroy(class_led, led_devno);		  //清除设备
	class_destroy(class_led);					  //清除类
	cdev_del(&led_chr_dev);						  //清除设备号
	unregister_chrdev_region(led_devno, DEV_CNT); //取消注册字符设备

	/*注销字符设备*/
	platform_driver_unregister(&led_platform_driver);

	printk(KERN_ALERT "led_platform_driver exit!\n");
}

module_init(led_platform_driver_init);
module_exit(led_platform_driver_exit);

MODULE_LICENSE("GPL");

/**/

总结

第三点get_dts_info.c仅为获取DTS属性信息演示代码。