platform总线、设备与驱动（2） return, 结构体, 动态

yuyang911220

代码清单5 为globalfifo添加platform_driver
1 static int __devinit globalfifo_probe(struct platform_device *pdev)
2 {
3 int ret;
4 dev_t devno = MKDEV(globalfifo_major, 0);
5
6 /* 申请设备号*/
7 if (globalfifo_major)
8 ret = register_chrdev_region(devno, 1, "globalfifo");
9 else { /* 动态申请设备号 */
10 ret = alloc_chrdev_region(&devno, 0, 1, "globalfifo");
11 globalfifo_major = MAJOR(devno);
12 }
13 if (ret < 0)
14 return ret;
15 /* 动态申请设备结构体的内存*/
16 globalfifo_devp = kmalloc(sizeof(struct globalfifo_dev), GFP_KERNEL);
17 if (!globalfifo_devp) { /*申请失败*/
18 ret = - ENOMEM;
19 goto fail_malloc;
20 }
21
22 memset(globalfifo_devp, 0, sizeof(struct globalfifo_dev));
23
24 globalfifo_setup_cdev(globalfifo_devp, 0);
25
26 init_MUTEX(&globalfifo_devp->sem); /*初始化信号量*/
27 init_waitqueue_head(&globalfifo_devp->r_wait); /*初始化读等待队列头*/
28 init_waitqueue_head(&globalfifo_devp->w_wait); /*初始化写等待队列头*/
29
30 return 0;
31
32 fail_malloc: unregister_chrdev_region(devno, 1);
33 return ret;
34 }
35
36 static int __devexit globalfifo_remove(struct platform_device *pdev)
37 {
38 cdev_del(&globalfifo_devp->cdev); /*注销cdev*/
39 kfree(globalfifo_devp); /*释放设备结构体内存*/
40 unregister_chrdev_region(MKDEV(globalfifo_major, 0), 1); /*释放设备号*/
41 return 0;
42 }
43
44 static struct platform_driver globalfifo_device_driver = {
45 .probe = globalfifo_probe,
46 .remove = __devexit_p(globalfifo_remove),
47 .driver = {
48 .name = "globalfifo",
49 .owner = THIS_MODULE,
50 }
51 };
52
53 static int __init globalfifo_init(void)
54 {
55 return platform_driver_register(&globalfifo_device_driver);
56 }
57
58 static void __exit globalfifo_exit(void)
59 {
60 platform_driver_unregister(&globalfifo_device_driver);
61 }
62
63 module_init(globalfifo_init);
64 module_exit(globalfifo_exit);
在代码清单5中，模块加载和卸载函数仅仅通过platform_driver_register()、 platform_driver_unregister()函数进行platform_driver的注册与注销，而原先注册和注销字符设备的工作已经被移交到platform_driver的probe()和remove()成员函数中。
代码清单5未列出的部分与原始的globalfifo驱动相同，都是实现作为字符设备驱动核心的file_operations的成员函数。