17-vmem_disk设备驱动block_device_operations及成员函数
13.7.3 vmem_disk设备驱动block_device_operations及成员函数
vmem_disk提供block_device_operations结构体中open()、release()、getgeo()、media_changed()、revalidate_disk()这些成员函数，代码清单13.18给出了vmem_disk设备驱动的blockdevice operations结构体定义及其成员函数的实现。
代码清单13.18 vmem.disk设备驱动block.device.operations结构体及成员函数
1 /*
2 * Open和close.
3 */
4
5 static int vmem_disk_open(struct block_device *bdev, fmode_t mode)
6 {
7 struct vmem_disk_dev *dev = bdev->bd_disk->private_data;
8
9 del_timer_sync(&dev->timer);
10 spin_lock(&dev->lock);
11 dev->users++;
12 spin_unlock(&dev->lock);
13
14 return 0;
15 }
16
17 static int vmem_disk_release(struct gendisk *disk, fmode_t mode)
18 {
19 struct vmem_disk_dev *dev = disk->private_data;
20
21 spin_lock(&dev->lock);
22 dev->users--;
23
24 if (!dev->users) {
25 dev->timer.expires = jiffies + INVALIDATE_DELAY;
26 add_timer(&dev->timer);
27 }
28 spin_unlock(&dev->lock);
29
30 return 0;
31 }
32
33 int vmem_disk_media_changed(struct gendisk *gd)
34 {
35 struct vmem_disk_dev *dev = gd->private_data;
36
37 return dev->media_change;
38 }
39
40 int vmem_disk_revalidate(struct gendisk *gd)
41 {
42 struct vmem_disk_dev *dev = gd->private_data;
43
44 if (dev->media_change) {
45 dev->media_change = 0;
46 memset (dev->data, 0, dev->size);
47 }
48 return 0;
49 }
50
51 /*
52 * invalidate()在定时器到期时执行，设置一个标志来模拟磁盘的移除
53 */
54 void vmem_disk_invalidate(unsigned long ldev)
55 {
56 struct vmem_disk_dev dev = (struct vmem_disk_dev ) ldev;
57
58 spin_lock(&dev->lock);
59 if (dev->users || !dev->data)
60 printk (KERN_WARNING "vmem_disk: timer sanity check failed\n");
61 else
62 dev->media_change = 1;
63 spin_unlock(&dev->lock);
64 }
65
66 /*
67 * getgeo() 实现
68 */
69
70 static int vmem_disk_getgeo(struct block_device bdev, struct hd_geometry geo)
71 {
72 long size;
73 struct vmem_disk_dev *dev = bdev->bd_disk->private_data;
74
75 size = dev->size*(hardsect_size/KERNEL_SECTOR_SIZE);
76 geo->cylinders = (size & ~0x3f) >> 6;
77 geo->heads = 4;
78 geo->sectors = 16;
79 geo->start = 4;
80
81 return 0;
82 }
83
84 /*
85 * block_device_operations结构体
86 */
87 static struct block_device_operations vmem_disk_ops = {
88 .owner = THIS_MODULE,
89 .open = vmem_disk_open,
90 .release = vmem_disk_release,
91 .media_changed = vmem_disk_media_changed,
92 .revalidate_disk = vmem_disk_revalidate,
93 .getgeo = vmem_disk_getgeo,
94 };