pcDuino day4

hello_module2.c

static int __init hello_init(void){    printk(DEVICE_NAME" Hello world in kernel module\n");    major = register_chrdev(0, DEVICE_NAME, &hello_fops);   //12位主设备号 20位次设备号    if(major < 0){        printk(DEVICE_NAME" register %s fial\n", DEVICE_NAME);        return major;    }    dev_class = class_create(THIS_MODULE, DEVICE_NAME);    if(dev_class == NULL)        printk("device node create fail\n");    else    {        dev_t dev = MKDEV(major, 0);        device_create(dev_class, NULL, MKDEV(major, 0), NULL, "hello"); //自动创建设备结点 /proc/device/    }    printk(DEVICE_NAME" got major number: %d\n", major);    return 0;}

hello_module_cdev.c

static int __init hello_init(void){    int result;    printk(DEVICE_NAME" Hello world in kernel module\n");    result = alloc_chrdev_region(&g_devno, 0, DEVICE_COUNT, DEVICE_NAME); //次设备 从0开始 数量DEVICE_COUNT个    if(result < 0)    {        printk("alloc_chrdev_region fail\n");        return result;    }    major = MAJOR(g_devno);    minor = MINOR(g_devno);    cdev_init(&g_cdev, &hello_fops);    g_cdev.ops = &hello_fops;    g_cdev.owner = THIS_MODULE;    result = cdev_add(&g_cdev, g_devno, DEVICE_COUNT);  //把设备号与字符设备关联    if(result)    {        printk("add cdev error\n");        unregister_chrdev_region(g_devno, DEVICE_COUNT); //添加失败 回收设备号        return result;    }    dev_class = class_create(THIS_MODULE, DEVICE_NAME);    if(dev_class == NULL)    {        printk("device node create fail\n");    }    else    {    //  dev_t dev = MKDEV(major, 0);        int i;        for(i = 0; i < DEVICE_COUNT; i++)            device_create(dev_class, NULL, g_devno + i, NULL, "%s%d", DEVICE_NAME, i); //自动创建设备结点 /proc/device/    }    printk(DEVICE_NAME" got major number: %d\n", major);    return 0;}