TQ210字符设备驱动——led驱动（cdev_add方式）

led_cdev.c:

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/device.h>//classcreate的定义
#include <linux/gpio.h>//gpio结构体的定义
#include <mach/regs-gpio.h>
//linux 3.10内核的regs-gpio.h位置不再是<asm/arch/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/cdev.h>

volatile unsigned long *gpc0con = NULL;
volatile unsigned long *gpc0pud = NULL;
volatile unsigned long *gpc0dat = NULL;

#define LED_MAJOR 0

static struct gpio leds_gpios[] = {
    { S5PV210_GPC0(3), GPIOF_OUT_INIT_LOW, "LED1" }, /* 默认为输出 */
    { S5PV210_GPC0(4),GPIOF_OUT_INIT_LOW, "LED2" } /* 默认为输出 */
};

static struct class *firstdrv_class;
static struct device *firstdrv_class_dev;

static int first_led_open(struct inode *inode, struct file *file)
{
    printk("first_drv_open\n");
    return 0;
}

static ssize_t first_led_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
    int val;
    int ret;
    printk("first_drv_write\n");
    ret = copy_from_user(&val, buf, count); //    copy_to_user();
    if(ret)
    {
        printk("copy_from_user error\n");
        return -EFAULT;
    }
    if (val == 1)
    {
        gpio_set_value( S5PV210_GPC0(3), 1);
        gpio_set_value( S5PV210_GPC0(4), 1);
    }
    else
    {
        gpio_set_value( S5PV210_GPC0(3), 0);
        gpio_set_value( S5PV210_GPC0(4), 0);
    }
    return 0;
}

static struct file_operations first_led_fops = {
    .owner = THIS_MODULE,
    .open = first_led_open,
    .write    =    first_led_write,
};

int major = 0;
dev_t devid;
struct cdev led_dev;
static int __init first_led_init(void)
{
    int err;
#if    0
    major = register_chrdev(0, "led_cdev", &first_led_fops);
#else
    /* 1. 分配设备号 */
    if(major){
        devid = MKDEV(major,0);
        major = MAJOR(devid);
        err = register_chrdev_region(devid,0,"led_cdev");//向系统注册一个已知的设备编号
    }
    else{
        printk("-> alloc_chrdev_region\n");
        err = alloc_chrdev_region(&devid,0,1,"led_cdev");//申请编号，主设备动态分配，次设备号为0，范围1，申请到的主设备号存放在devid中
    }

    if(err){
        printk(KERN_WARNING "led:can't get major %d\n",LED_MAJOR);
        return err;
    }
    /* 2. 根据设备号注册设备 */
    led_dev.owner = THIS_MODULE;
    cdev_init(&led_dev, &first_led_fops);//构造字符设备结构体cdev led_dev
    err = cdev_add(&led_dev,devid,1); //cdev_add(&led_dev,dev_t,count)，注册字符设备
    if(err){
        printk("cdev_add error !");
        return err;
    }
#endif
    /* 3. 建立设备节点，用deice_create自动创建 */
    //MKDEV将主设备号和次设备号转为dev_t类型
    //device_create创建设备信息，udev会自动根据设备信息创建设备节点/dev/xyz，应用程序根据设备节点(路径)访问设备
    //linux 3.10中，class_device_create替换为device_create
    //major = MAJOR(devid);//提取申请到的主设备号
    firstdrv_class = class_create(THIS_MODULE,"class_led_cdev");
    firstdrv_class_dev = device_create(firstdrv_class, NULL,devid, NULL, "xyz");

    err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));//申请GPIO
    if (err){
        printk("gpio_request_array error\n");
        return -EFAULT;
    }
    printk("led initialize\n");
    return 0;
}

static void __exit first_led_exit(void)
{
    printk("first_led_exit\n");
    gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));//释放GPIO
#if 0
    unregister_chrdev(major, "led_cdev");
#else
    unregister_chrdev_region(devid, 1);//释放设备编号unregister_chrdev_region(dev_t from, unsigned count)
    cdev_del(&led_dev); //删除字符设备
#endif
    device_unregister(firstdrv_class_dev);//linux 3.10中，class_device_unregister替换为device_unregister
    class_destroy(firstdrv_class);
}

module_init(first_led_init);
module_exit(first_led_exit);

MODULE_LICENSE("GPL");

ledtest.c:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

/* firstdrvtest on
  * firstdrvtest off
  */
int main(int argc, char **argv)
{
    int fd;
    int val = 1;
    fd = open("/dev/xyz", O_RDWR);
    if (fd < 0)
    {
        printf("can't open!\n");
    }
    if (argc != 2)
    {
        printf("Usage :\n");
        printf("%s <on|off>\n", argv[0]);
        return 0;
    }

    if (strcmp(argv[1], "on") == 0)
    {
        val = 1;
    }
    else
    {
        val = 0;
    }

    write(fd, &val, 4);
    return 0;
}

Makefile:

KERN_DIR = /home/richard/work/kernel/linux-3.10.80
obj-m += led_cdev.o

all:
make -C $(KERN_DIR) M=`pwd` modules
clean:
rm -rf *.ko *.mod.c *.mod.o *.o *.order *.symvers *.cmd .*.o.* .*.ko.*

具体代码分析可参考LDD3或者宋宝华老师书籍或者韦东山的视频