register_chrdev() ／register_chrdev_region()／ alloc_chrdev_region

[转]

分配设备编号，注册设备与注销设备的函数均在fs.h中申明，如下：
extern int register_chrdev_region(dev_t, unsigned, const char *);
extern int register_chrdev(unsigned int, const char *,
               struct file_operations *);
extern int unregister_chrdev(unsigned int, const char *);
extern void unregister_chrdev_region(dev_t, unsigned);

在fs/char_dev.c中定义：
其原型如下：分配设备编号的2个，注销设备编号的1个，注册设备的1个，注销设备的1个。
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注册设备：
int register_chrdev(unsigned int major, const char *name,
            struct file_operations *fops)
{
    struct char_device_struct *cd;
    struct cdev *cdev;
    char *s;
    int err = -ENOMEM;

    cd = __register_chrdev_region(major, 0, 256, name);
    if (IS_ERR(cd))
        return PTR_ERR(cd);
    
    cdev = cdev_alloc();
    if (!cdev)
        goto out2;

    cdev->owner = fops->owner;
    cdev->ops = fops;
    kobject_set_name(&cdev->kobj, "%s", name);
    for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
        *s = '!';
        
    err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
    if (err)
        goto out;

    cd->cdev = cdev;

    return major ? 0 : cd->major;
out:
    kobject_put(&cdev->kobj);
out2:
    kfree(__unregister_chrdev_region(cd->major, 0, 256));
    return err;
}
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分配设备编号：
int register_chrdev_region(dev_t from, unsigned count, const char *name)
{
    struct char_device_struct *cd;
    dev_t to = from + count;
    dev_t n, next;

    for (n = from; n < to; n = next) {
        next = MKDEV(MAJOR(n)+1, 0);
        if (next > to)
            next = to;
        cd = __register_chrdev_region(MAJOR(n), MINOR(n),
                   next - n, name);
        if (IS_ERR(cd))
            goto fail;
    }
    return 0;
fail:
    to = n;
    for (n = from; n < to; n = next) {
        next = MKDEV(MAJOR(n)+1, 0);
        kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
    }
    return PTR_ERR(cd);
}
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动态分配设备编号：
int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
            const char *name)
{
    struct char_device_struct *cd;
    cd = __register_chrdev_region(0, baseminor, count, name);
    if (IS_ERR(cd))
        return PTR_ERR(cd);
    *dev = MKDEV(cd->major, cd->baseminor);
    return 0;
}
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注销设备编号：
void unregister_chrdev_region(dev_t from, unsigned count)
{
    dev_t to = from + count;
    dev_t n, next;

    for (n = from; n < to; n = next) {
        next = MKDEV(MAJOR(n)+1, 0);
        if (next > to)
            next = to;
        kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
    }
}
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注销设备：
int unregister_chrdev(unsigned int major, const char *name)
{
    struct char_device_struct *cd;
    cd = __unregister_chrdev_region(major, 0, 256);
    if (cd && cd->cdev)
        cdev_del(cd->cdev);
    kfree(cd);
    return 0;
}
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