实例：vmem_disk设备驱动的block_device_operations(3)

vmem_disk提供block_device_operations结构体中的getgeo()成员函数。如下给出了vmem_disk设备驱动的block_device_operations结构体定义及其成员函数的实现。

static int vmem_disk_getgeo(struct block_device *bdev,struct hd_geometry *geo)
{
	long size;
	struct vmem_disk_dev *dev = bdev->bd_disk->private_data;
	size = dev->size*(HARDSECT_SIZE/KERNEL_SECTOR_SIZE);
	geo->cylinders = (size & ~0x3f) >> 6;
	geo->heads = 4;
	geo->sector = 16;
	geo->start=4;
	
	return 0;	
}
static struct block_device_operations vmem_disk_ops = {
	.getgeo = vmem_disk_getgeo;
};