驱动：3.3ioctl

用户空间：
使用ioctl可以用来设置、获取设备的工作属性参数
ioctl（fd，cmd）；
ioctl（fd，cmd，&arg）；
内核空间：
.unlocked_ioctl = led_ioctl 为成员变量函数指针赋值

实验步骤：

vi led_drv.c

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#define LED_ON  0x10001
#define LED_OFF 0x10002
/*
 *./test <on/off> <1/2/3/4>
 * */
int main(int argc, char *argv[])
{
    int fd = 0;
    int cmd = 0;
    int index = 0;
    if(argc != 3)
    {
        printf("usage: %s <on/off> <1/2/3/4>\n", argv[0]);
        return -1;
    }
    fd = open("/dev/myleds", O_RDWR);
    if(fd < 0)
    {
        perror("open failed");
        return -1;
    }
    printf("open myleds successed!\n");
    if(strcmp(argv[1], "on") == 0)
        cmd = 0x10001;
    else if(strcmp(argv[1], "off") == 0)
        cmd = 0x10002;
    else
        return -1;
    index = strtoul(argv[2], NULL, 0);
    if(index>4)
    {
        printf("usage: %s <on/off> <1/2/3/4>\n", argv[0]);
        return -1;
    }
    ioctl(fd, cmd, &index);
    close(fd);
    return 0;
}

vi test.c

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

MODULE_LICENSE("GPL");

#define LED_ON  (0x10001)
#define LED_OFF (0x10002)

dev_t dev; //设备号
unsigned int major = 0; //主设备号
unsigned int minor = 5; //次设备号

struct cdev led_cdev;

typedef struct led_desc
{
    char *name;//名称
    int gpio;//管脚编号
}led_desc_t;

led_desc_t leds[]=
{
    {"led1", PAD_GPIO_C+12},
    {"led2", PAD_GPIO_C+7},
    {"led3", PAD_GPIO_C+11},
    {"led4", PAD_GPIO_B+26},
};

int led_open(struct inode *inode, struct file *filp)
{
    return 0;
}
int led_release(struct inode *inode, struct file *filp)
{
    return 0;
}
ssize_t led_write(struct file *filp, const char __user *buf, 
                  size_t len, loff_t *offset)
{
    return len;
}
ssize_t led_read(struct file *filp, char __user *buf, 
                  size_t len, loff_t *offset)
{
    return len;
}
long led_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    int k_index = 0;
    int ret = 0;
    /*arg 4字节内存 其中存储了用户空间变量index的地址
     *我们需要知道该地址对应的内存中存储的是1/2/3/4
     *需要通过读取该内存空间才能知道其中存储的值
     * */
    ret = copy_from_user(&k_index, (const void __user *)arg, 4);
    if(k_index>4)
    {
        return -EINVAL;
    }
    if(cmd == LED_ON){
        gpio_set_value(leds[k_index-1].gpio, 0);
    }else if(cmd == LED_OFF){
        gpio_set_value(leds[k_index-1].gpio, 1);
    }else{
        return -EINVAL;
    }
    return 0;
}
struct file_operations led_fops =
{
    .owner = THIS_MODULE,
    .open = led_open,
    .release = led_release, 
    .write = led_write,
    .read = led_read, 
    .unlocked_ioctl = led_ioctl,
};
int __init led_drv_init(void)
{
    int i = 0;
    if(major)//静态
    {
        /*注册设备号*/
        //dev = major<<20|minor;
        dev = MKDEV(major, minor);
        register_chrdev_region(dev, 1, "myleds");
    }
    else //动态
    {
        alloc_chrdev_region(&dev, minor, 1, "myleds");
        printk("<2>"  "major=%d minor=%d\n", MAJOR(dev), MINOR(dev));
    }
    /*初始化cdev变量*/
    cdev_init(&led_cdev, &led_fops);
    /*注册cdev变量*/
    cdev_add(&led_cdev, dev, 1);
    for(; i<ARRAY_SIZE(leds); i++)
    {
        /*申请GPIO管脚*/
        gpio_request(leds[i].gpio, leds[i].name);
        /*设置为输出模式*/
        gpio_direction_output(leds[i].gpio, 1);
    }
    return 0;
}
void __exit led_drv_exit(void)
{
    int i = 0;
    for(; i<ARRAY_SIZE(leds); i++)
    {
        /*释放GPIO管脚*/
        gpio_free(leds[i].gpio);
    }
    /*注销cdev变量*/
    cdev_del(&led_cdev);
    /*注销设备号*/
    unregister_chrdev_region(dev, 1);
}
module_init(led_drv_init);
module_exit(led_drv_exit);

make
arm-cortex_a9-linux-gnueabi-gcc test.c
cp led_drv.ko ../../rootfs/
cp a.out ../../rootfs/
开发板执行
          rmmod led_drv
          nsmod led_drv.ko
          mknod /dev/myleds c 243 5
          ./test on 1
          ./test off 1