字符设备驱动程序设计中的数据结构：struct file?用法看的迷糊啊

This declaration uses the standard C tagged structure initialization syntax. This syntax is preferred because it makes drivers more portable across changes in the definitions of the structures and, arguably, makes the code more compact and readable. Tagged initialization allows the reordering of structure members; in some cases, substantial performance improvements have been realized by placing pointers to frequently accessed members in the same hardware cache line.

The tagged structure initialization syntax allow you to initialize structure member in any order. So your code have no need to be modified  after the change of member definition order. And this feature has been a part of C standard since 1999.

struct file_operations mem_fops = {
    .owner = THIS_MODULE,
    .llseek = mem_seek,
    .read = mem_read,
    .write = mem_write,
    .ioctl = mem_ioctl,
    .open = mem_open,
    .release = mem_release,
};

.owner, .llseek and others are all the member tags.

For example:
struct foo{
int a;
int b;
};

You can declaration and initialize structure variable like this:

struct foo bar{
       .a = 1;
       .b = 2;
};

or in the other order:
struct foo bar{
       .b = 2;
       .a = 1;
};

Have you got it ?

[[it] 本帖最后由 rootkit 于 2008-11-7 15:42 编辑 [/it]]