修改设备树文件

开发板对应的设备树文件为imx6ull-alientek-emmc.dts
对应的linux源码的/arch/arm/boot/dts
在根节点下创建一个alphaled的子节点，创建的内容如下。

alphaled{
    #address-cells = <1>;          //表示 reg 属性中起始地址占用一个字长
    #size-cells = <1>;             //表示 reg 属性中地址长度占用一个字长
    compatible = "atkalpha-led";   //设置节点兼容性为“atkalpha-led”
    status = "okay";               //状态为“okay”
    reg = <    0X020C406C  0X04    //寄存器CCM_CCGR1_BASE物理地址
               0X020E0068  0X04    //寄存器SW_MUX_GPIO1_IO03_BASE物理地址
               0X020E02F4  0X04    //寄存器SW_PAD_GPIO1_IO03_BASE物理地址
               0X0209C000  0X04    //寄存器GPIO1_DR_BASE物理地址
               0X0209C004  0X04 >; //寄存器GPIO1_GDIR_BASE物理地址
};

编译设备树

    make dtbs

编译完成后可以在 源码/arch/arm/boot/dts下看到新的imx6ull-alientek-emmc.dtb。将新的设备树文件烧录在板子上，启动板子可以在/proc/device-tree/目录下查看到alphaled这个节点

驱动程序编写

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

#define DTSLED_CNT  1            /*设备号个数*/
#define DTSLED_NAME "dtsled"    /*设备名称*/
#define LEDOFF  0                /*开灯*/
#define LEDON   1                /*关灯*/

/*映射后的寄存器虚拟地址*/
static void __iomem *IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;

/*dtsled设备结构体*/
struct dtsled_dev{
    dev_t   devid;            /*设备号*/            
    struct cdev cdev;        /*cdev*/
    struct class *class;    /*类*/
    struct device *device;    /*设备*/
    int major;                /*主设备号*/
    int minor;                /*次设备号*/
    struct device_node *nd;    /*设备节点*/
};

struct dtsled_dev dtsled; /*dtsled设备*/


/*LED开关函数*/
void led_switch(u8 sta)
{
    u32 val = 0;

    if(sta == LEDON){
        val = readl(GPIO1_DR);
        val &= ~(1<<3); 
        writel(val, GPIO1_DR);
    }else if(sta == LEDOFF){
        val = readl(GPIO1_DR);
        val |= (1<<3);
        writel(val, GPIO1_DR);
    }
}

/*打开涉笔*/
static int led_open(struct inode *inode, struct file *filp)
{
    filp->private_data = &dtsled;/*设置私有数据*/
    return 0;
}

/*从设备读取数据*/
static ssize_t led_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{

    return 0;
}
/*向设备写数据*/
static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
    int retvalue = 0;
    u8 databuf[4] = {0};
    u8 ledstat = 0;

    retvalue = copy_from_user(databuf, buf, cnt);
    if(retvalue < 0){
        printk("Kernel write failed!\r\n");
        return -EFAULT;
    }else{
        printk("Kernel write %d success!\r\n", databuf[0]);
    }

    ledstat = databuf[0];
    if(ledstat == LEDOFF){
        led_switch(LEDOFF);
    }else if(ledstat == LEDON){
        led_switch(LEDON);
    }
    return 0;
}

/*关闭设备*/
static int led_release(struct inode *inode, struct file *filp)
{
    return 0;
}

/*设备操作函数*/
static struct file_operations dtsled_fops = {
    .owner = THIS_MODULE,
    .open = led_open,
    .read = led_read,
    .write = led_write,
    .release = led_release,    
};


/*LED硬件初始化*/
static void led_hw_init(u32 *regdata, struct device_node *nd)
{
    u32 val = 0;
    /*寄存器地址映射*/
#if 0
    IMX6U_CCM_CCGR1 = ioremap(regdata[0], regdata[1]);
    SW_MUX_GPIO1_IO03 = ioremap(regdata[2], regdata[3]);
    SW_PAD_GPIO1_IO03 = ioremap(regdata[4], regdata[5]);
    GPIO1_DR = ioremap(regdata[6], regdata[7]);
    GPIO1_GDIR = ioremap(regdata[8], regdata[9]);
#else
    IMX6U_CCM_CCGR1 = of_iomap(nd, 0);
    SW_MUX_GPIO1_IO03 = of_iomap(nd, 1);
    SW_PAD_GPIO1_IO03 = of_iomap(nd, 2);
    GPIO1_DR = of_iomap(nd, 3);
    GPIO1_GDIR = of_iomap(nd, 4);
#endif

    /*使能GPIO1时钟*/
    val = readl(IMX6U_CCM_CCGR1);
    val &= ~(3<<26);
    val |= (3<<26);
    writel(val, IMX6U_CCM_CCGR1);
    
    /*设置GPIO1_IO03的复用功能*/
    writel(5, SW_MUX_GPIO1_IO03);
    
    /*设置IO属性*/
    writel(0x10B0, SW_PAD_GPIO1_IO03);
    
    /*设置IO为输出功能*/
    val = readl(GPIO1_GDIR);
    val &= ~(1<<3);
    val |= (1<<3);
    writel(val, GPIO1_GDIR);
    
    /*关闭LED*/
    val = readl(GPIO1_DR);
    val |= (1<<3);
    writel(val, GPIO1_DR);
    printk("led hw init done\r\n");
}

/*LED硬件反初始化*/
static void led_hw_deinit(void)
{
    /*取消映射*/
    iounmap(IMX6U_CCM_CCGR1);
    iounmap(SW_MUX_GPIO1_IO03);
    iounmap(SW_PAD_GPIO1_IO03);
    iounmap(GPIO1_DR);
    iounmap(GPIO1_GDIR);
}

/*驱动入口函数*/
static int __init led_init(void)
{
    int i = 0;
    int ret = 0;
    u32 regdata[10] = {0};
    struct property *proper = NULL;
    const char *str;

    /*获取设备树中的属性数据*/
    /*1.获取设备节点:alphaled*/
    dtsled.nd = of_find_node_by_path("/alphaled"); //通过路径来查找指定的节点
    if(dtsled.nd == NULL){
        printk("alphaled node can not found!\r\n");
        return -EINVAL;
    }else{
        printk("alphaled node has been found!\r\n");
    }
    
    /*2.获取compatible属性内容*/
    proper = of_find_property(dtsled.nd, "compatible", NULL);//查找指定的属性
    if(proper == NULL){
        printk("compatible property find failed\r\n");
    }else{
        printk("compatible = %s\r\n", (char*)proper->value);
    }
    
    /*3.获取status属性内容*/
    ret = of_property_read_string(dtsled.nd, "status", &str);//用于读取属性中字符串值
    if(ret < 0){
        printk("status read failed!\r\n");
    }else{
        printk("status = %s\r\n", str);
    }
    
    /*获取reg属性内容*/
    ret = of_property_read_u32_array(dtsled.nd, "reg", regdata, 10);//读取属性中u32类型的数组数据
    if(ret < 0){
        printk("reg property read failed!\r\n");
    }else{
        printk("reg data:\r\n");
        for(i=0; i<10; i++){
            printk("%#X ", regdata[i]);
        }
        printk("\r\n");
    }

    /*初始化LED*/
    led_hw_init(regdata, dtsled.nd);

    /*1.创建设备号*/
    if(dtsled.major){/*定义了设备号*/
        dtsled.devid = MKDEV(dtsled.major, 0);
        register_chrdev_region(dtsled.devid, DTSLED_CNT, DTSLED_NAME);
    }else{/*内有定义了设备号*/
        alloc_chrdev_region(&dtsled.devid, 0, DTSLED_CNT, DTSLED_NAME);/*申请设备号*/
        dtsled.major = MAJOR(dtsled.devid);/*获取分配号的主设备号*/
        dtsled.minor = MINOR(dtsled.devid);/*获取分配号的次设备号*/
    }
    printk("dtsled major = %d, minor = %d\r\n", dtsled.major, dtsled.minor);
    
    /*初始化cdev*/
    dtsled.cdev.owner = THIS_MODULE;
    cdev_init(&dtsled.cdev, &dtsled_fops);

    /*向内核中添加一个cdev*/
    cdev_add(&dtsled.cdev, dtsled.devid, DTSLED_CNT);

    /*创建类*/
    dtsled.class = class_create(THIS_MODULE, DTSLED_NAME);
    if(IS_ERR(dtsled.class)){
        return PTR_ERR(dtsled.class);
    }
    /*创建设备*/
    dtsled.device = device_create(dtsled.class, NULL, dtsled.devid, NULL, DTSLED_NAME);
    if(IS_ERR(dtsled.device)){
        return PTR_ERR(dtsled.device);
    }

    return 0;
}


/*驱动出口函数*/
static void __exit led_exit(void)
{
    led_hw_deinit();
    /*注销字符设备驱动*/
    cdev_del(&dtsled.cdev);/*删除cdev*/
    unregister_chrdev_region(dtsled.devid, DTSLED_CNT);/*注销设备号*/

    device_destroy(dtsled.class, dtsled.devid);/*设备的销毁*/
    class_destroy(dtsled.class);/*类的销毁*/
}

module_init(led_init);
module_exit(led_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("warren");

测试程序编写

#include "stdio.h"
#include "unistd.h"
#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "stdlib.h"
#include "string.h"

#define LEDOFF 0 
#define LED_ON 1

int main(int argc, int **argv)
{
    int fd = 0;
    int retvalue = 0;
    char *filename = NULL;
    unsigned char databuf[1];

    if(argc != 3){
        printf("Error Usage!\r\n");
        return -1;
    }
    filename = argv[1];
    fd = open(filename, O_RDWR);
    if(fd < 0){
        printf("faile %s open failed!\r\n", filename);
        return -1;
    }
    databuf[0] = atoi(argv[2]);
    retvalue = write(fd, databuf, sizeof(databuf));
    if(retvalue < 0){
        printf("LED Control Failed!\r\n");
        close(fd);
        return -1;
    }
    retvalue = close(fd);
    if(retvalue < 0){
        printf("file %s close failed!\r\n", filename);
        return -1;
    }
    return 0;
}

程序编译

KERNELDIR    :=    /home/warren/linux/linux_source_code/linux-imx-rel_imx_4.1.15_2.1.0_ga_alientek
CURRENT_PATH    :=    $(shell pwd)
obj-m    :=    dtsled.o
build:    kernel_modules

kernel_modules:
    $(MAKE)    -C    $(KERNELDIR)    M=$(CURRENT_PATH)    modules
clean:
    $(MAKE)    -C    $(KERNELDIR)    M=$(CURRENT_PATH)    clean

arm-linux-gnueabihf-gcc ledApp.c -o ledApp

程序测试

将编译完成后的dtsled.ko文件放在/lib/modules/4.1.15-g06f53e4下
使用depmod命令扫描设备中的驱动
使用modprobe dtsled命令加载命令
可以看到如下打印

到/dev下可以查看到驱动文件

将编译完成后的ledApp文件放在home下。调用ledApp可以实现开灯与关灯

./ledApp /dev/dtsled 1 /*开灯*/
./ledApp /dev/dtsled 0 /*关灯*/