17、设备树实验

一、设备树

    /*添加led_test节点,*/
    led_test{
        #address-cells = <1>;
        #size-cells = <1>;
        compatible = "led_test";
        ranges;
        //例程是系统灯GPIO0_C7
        led@0xfdd60004{
            reg = <0xfdd60004 0x00000004 0xfdd6000C 0x00000004>;          //GPIO0_H 的数据寄存器和数据方向寄存器
            status = "okay";
        };
    };

二、驱动

#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 <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 "led_test"
#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; //led的设备树节点
    void __iomem *va_DR;
    void __iomem *va_DDR;
};

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 *led_test_device_node;         //led_test的设备树节点结构体

/*定义led灯的led_resource 结构体，保存获取得到的节点信息*/
struct led_resource led_res;

/*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 led_chr_dev_open \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)
{

    unsigned int register_data = 0; //暂存读取得到的寄存器数据
    unsigned char write_data; //用于保存接收到的数据

    int error = copy_from_user(&write_data, buf, cnt);
    if (error < 0)
    {
        return -1;
    }
    /*设置led引脚 输出电平*/
    if (write_data)
    {
        register_data |= ((unsigned int)0x1 << (23));
        register_data |= ((unsigned int)0x1 << (7));
        writel(register_data, led_res.va_DR); // GPIO0_C7引脚输出高电平，红灯灭
    }
    else
    {
        register_data |= ((unsigned int)0x1 << (23));
        register_data &= ~((unsigned int)0x1 << (7));
        writel(register_data, led_res.va_DR); // GPIO0_C7引脚输出低电平，红灯亮
    }

    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,
        .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_EMERG "\t  match successed  \n");

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

    /*获取led节点*/
    led_res.device_node = of_find_node_by_name(led_test_device_node,"led");
    if (led_res.device_node == NULL)
    {
        printk(KERN_ERR "\n get led_device_node failed ! \n");
        return -1;
    }

    /*获取 reg 属性并转化为虚拟地址*/
    led_res.va_DR = of_iomap(led_res.device_node, 0);
    if(led_res.va_DR == NULL){
            printk("of_iomap is error \n");
            return -1;
    }

    led_res.va_DDR = of_iomap(led_res.device_node, 1);
    if(led_res.va_DDR == NULL){
                printk("of_iomap is error \n");
                return -1;
        }

    // 设置模式寄存器：输出模式
    register_data = readl(led_res.va_DDR);
    register_data |= ((unsigned int)0x1 << (23));
    register_data |= ((unsigned int)0x1 << (7));
    writel(register_data,led_res.va_DDR);

    // 设置置位寄存器：默认输出高电平
    register_data = readl(led_res.va_DR);
    register_data |= ((unsigned int)0x1 << (23));
    register_data |= ((unsigned int)0x1 << (7));
    writel(register_data, led_res.va_DR);

    /*---------------------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，
    //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 led_ids[] = {
    {.compatible = "led_test"},
    {/* sentinel */}
};

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

/*
*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_EMERG "\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_res.va_DR);
    iounmap(led_res.va_DDR);

    /*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_EMERG "dts test led exit!\n");
}

module_init(led_platform_driver_init);
module_exit(led_platform_driver_exit);

MODULE_LICENSE("GPL");

解析：

/**
 * of_iomap - Maps the memory mapped IO for a given device_node
 * @device:     the device whose io range will be mapped
 * @index:      index of the io range
 *
 * Returns a pointer to the mapped memory
 */
void __iomem *of_iomap(struct device_node *np, int index)
{
        struct resource res;

        if (of_address_to_resource(np, index, &res))
                return NULL;

        return ioremap(res.start, resource_size(&res));
}
EXPORT_SYMBOL(of_iomap);

int of_address_to_resource(struct device_node *dev, int index,
                           struct resource *r)
{
        const __be32    *addrp;
        u64             size;
        unsigned int    flags;
        const char      *name = NULL;

        addrp = of_get_address(dev, index, &size, &flags);
        if (addrp == NULL)
                return -EINVAL;

        /* Get optional "reg-names" property to add a name to a resource */
        of_property_read_string_index(dev, "reg-names", index, &name);

        return __of_address_to_resource(dev, addrp, size, flags, name, r);
}
EXPORT_SYMBOL_GPL(of_address_to_resource);

of_get_address

__of_address_to_resource

三、APP

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
int main(int argc, char *argv[])
{
    printf("led test_app\n");

    /*判断输入的命令是否合法*/
    if(argc != 2)
    {
        printf(" command error ! \n");
        printf(" usage : sudo test_app num [num can be 0 or 1]\n");
        return -1;
    }

    /*打开文件*/
    int fd = open("/dev/led_test", O_RDWR);
    if(fd < 0)
    {
        printf("open file : %s failed !\n", argv[0]);
        return -1;
    }

    unsigned char commend = atoi(argv[1]);  //将接收值转化为数字;

    /*写入命令*/
    int error = write(fd,&commend,sizeof(commend));
    if(error < 0)
    {
        printf("write file error! \n");
        close(fd);
        /*判断是否关闭成功*/
    }

    /*关闭文件*/
    error = close(fd);
    if(error < 0)
    {
        printf("close file error! \n");
    }

    return 0;
}