使用linux-2.6.30.4。
文件的管理使用的是 sysfs.(由udev製作的文件系統)
涉及兩個函數:
virtual_disk_class = class_create(THIS_MODULE, "VirtualDisk");
device_create( virtual_disk_class, NULL, devno, 0, "VirtualDisk");
使用需添加頭文件 #include <linux/device.h>
說明:
當使用利用udev製作的文件系統時,Linux內核爲我們提供了一組函數,可以用來在模塊加載的時候自動在/dev目錄下創建相應設備節點,並在卸載模塊時刪除該節點。
內核中定義了struct class結構體,一個struct class結構體類型變量對應一個類(有待商榷),內核同時提供了class_create(…)函數,可以用它來創建一個類,這個類存放於sysfs下面,一旦創建好了這個類,再調用device_create(…)函數來在/dev目錄下創建相應的設備節點。這樣,加載模塊的時候,用戶空間中的udev會自動響應device_create(…)函數,去/sysfs下尋找對應的類從而創建設備節點。
在linux-2.6.30.4,struct class定義在頭文件include/linux/device.h中,
struct class {
const char *name;
struct module *owner;
struct class_attribute *class_attrs;
struct device_attribute *dev_attrs;
struct kobject *dev_kobj;
int (*dev_uevent)(struct device *dev, struct kobj_uevent_env *env);
void (*class_release)(struct class *class);
void (*dev_release)(struct device *dev);
int (*suspend)(struct device *dev, pm_message_t state);
int (*resume)(struct device *dev);
struct dev_pm_ops *pm;
struct class_private *p;
};
class_create(…)頭文件include/linux/device.h中,
#define class_create(owner, name) /
({ /
static struct lock_class_key __key; /
__class_create(owner, name, &__key); /
})
__class_create在/drivers/base/class.c中實現:
struct class *__class_create(struct module *owner, const char *name,
struct lock_class_key *key)
device_create(…)函數在/drivers/base/core.c中實現:
struct device *device_create(struct class *class, struct device *parent,
dev_t devt, void *drvdata, const char *fmt, ...)
* device_create - creates a device and registers it with sysfs
* @class: pointer to the struct class that this device should be registered to
* @parent: pointer to the parent struct device of this new device, if any
* @devt: the dev_t for the char device to be added
* @drvdata: the data to be added to the device for callbacks
* @fmt: string for the device's name
使用示例:
virtual_disk_class = class_create(THIS_MODULE, "VirtualDisk");
device_create( virtual_disk_class, NULL, devno, 0, "VirtualDisk");
示例程序(一個簡單的字符驅動):
struct class *virtual_disk_class; /*by yinhf.*/
/*設備驅動模塊加載函數*/
int VirtualDisk_init(void)
{
int result;
dev_t devno = MKDEV(VirtualDisk_major, 0); /*構建設備號*/
/* 申請設備號*/
if (VirtualDisk_major) /* 如果不爲0,則靜態申請*/
result = register_chrdev_region(devno, 1, "VirtualDisk");
else /* 動態申請設備號 */
{
result = alloc_chrdev_region(&devno, 0, 1, "VirtualDisk");
VirtualDisk_major = MAJOR(devno);/* 從申請設備號中得到主設備號 */
}
if (result < 0)
return result;
/* 動態申請設備結構體的內存*/
Virtualdisk_devp = kmalloc(sizeof(struct VirtualDisk), GFP_KERNEL);
if (!Virtualdisk_devp) /*申請失敗*/
{
result = - ENOMEM;
goto fail_kmalloc;
}
memset(Virtualdisk_devp, 0, sizeof(struct VirtualDisk));/*將內存清零*/
/*初始化並且添加cdev結構體*/
VirtualDisk_setup_cdev(Virtualdisk_devp, 0);
// devfs_mk_cdev(devno, S_IFCHR|S_IRUGO|S_IWUSR, "VirtualDisk"); /*yinhf*/
printk(KERN_ALERT "Virtualdisk Success/n");
/* create virtual_disk_class under /sysfs by yinhf.*/
virtual_disk_class = class_create(THIS_MODULE, "VirtualDisk");
if(IS_ERR(virtual_disk_class))
{
printk("Err: failed in creating virtual_disk_class./n");
return -1;
}
/* register your own device in sysfs, and this will cause udev to create corresponding device node */
device_create( virtual_disk_class, NULL, devno, 0, "VirtualDisk");
printk (KERN_INFO "Registered character driver VirtualDisk./n");
/*end create virtual_disk_class by yinhf.*/
return 0;
fail_kmalloc:
unregister_chrdev_region(devno, 1);
return result;
}
/*模塊卸載函數*/
void VirtualDisk_exit(void)
{
cdev_del(&Virtualdisk_devp->cdev); /*註銷cdev*/
kfree(Virtualdisk_devp); /*釋放設備結構體內存*/
device_destroy(virtual_disk_class, MKDEV(VirtualDisk_major, 0)); //delete device node under /dev
class_destroy(virtual_disk_class); //delete class created by us
unregister_chrdev_region(MKDEV(VirtualDisk_major, 0), 1); /*釋放設備號*/
}
參考網址:
http://blog.csdn.net/engerled/archive/2011/02/24/6205722.aspx