ARM-Linux驱动--MTD驱动分析(二)
来源:互联网 发布:数据库设计与实现 编辑:程序博客网 时间:2024/06/05 08:22
主机:Gentoo Linux 11.2 with linux kernel 3.0.6
硬件平台:FL2440(S3C2440)with linux kernel 2.6.35
原创作品,转载请标明出处http://blog.csdn.net/yming0221/article/details/7205713
*接上文 ARM-Linux驱动--MTD驱动分析(一)
1、mtd_notifier结构体
- //MTD设备通知结构体
- struct mtd_notifier {
- void (*add)(struct mtd_info *mtd);//加入MTD原始/字符/块设备时执行
- void (*remove)(struct mtd_info *mtd);//移除MTD原始/字符/块设备时执行
- struct list_head list;//list是双向链表,定义在include/linux/list.h
- };
INIT_LIST_HEAD(ptr) 初始化ptr节点为表头,将前趋与后继都指向自己。
LIST_HEAD(name) 声明并初始化双向循环链表name。
static inline void __list_add(struct list_head *new, struct list_head *prev, struct list_head *next)
向链表中在prev与next之间插入元素new
static inline void list_add(struct list_head *new, struct list_head *head)
在链表中头节点后插入元素new,调用__list_add()实现。
static inline void list_add_tail(struct list_head *new, struct list_head *head)
在链表末尾插入元素new,调用__list_add()实现。
static inline void __list_del(struct list_head * prev, struct list_head * next)
删除链表中prev与next之间的元素。
static inline void list_del(struct list_head *entry)
删除链表中的元素entry。
static inline void list_del_init(struct list_head *entry)
从链表中删除元素entry,并将其初始化为新的链表。
static inline void list_move(struct list_head *list, struct list_head *head)
从链表中删除list元素,并将其加入head链表。
static inline void list_move_tail(struct list_head *list, struct list_head *head)
把list移动到链表末尾。
static inline int list_empty(const struct list_head *head)
测试链表是否为空。
static inline void __list_splice(struct list_head *list, struct list_head *head)
将链表list与head合并。
static inline void list_splice(struct list_head *list, struct list_head *head)
在list不为空的情况下,调用__list_splice()实现list与head的合并。
static inline void list_splice_init(struct list_head *list, struct list_head *head)
将两链表合并,并将list初始化。
list_entry(ptr, type, member)
list_entry的定义是怎么回事?
a. list_entry的定义在内核源文件include/linux/list.h中:
#define list_entry(ptr, type, member)
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
b. 其功能是根据list_head型指针ptr换算成其宿主结构的起始地址,该宿主结构是type型的,而ptr在其宿主结构中定义为member成员。
2、add_mtd_device函数
- /**
- * add_mtd_device - register an MTD device
- * @mtd: pointer to new MTD device info structure
- *
- * Add a device to the list of MTD devices present in the system, and
- * notify each currently active MTD 'user' of its arrival. Returns
- * zero on success or 1 on failure, which currently will only happen
- * if there is insufficient memory or a sysfs error.
- */
- //添加MTD设备函数,将MTD设备加入MTD设备链表,并通知所有的MTD user该MTD设备。返回0表示成功,返回1表示出错(内存不足或文件系统错误)
- int add_mtd_device(struct mtd_info *mtd)
- {
- struct mtd_notifier *not;//定义一个MTD设备通知器
- int i, error;
- //下面是设置mtd_info结构体信息
- if (!mtd->backing_dev_info) {
- switch (mtd->type) {
- case MTD_RAM://MTD_RAM定义在include/mtd/mtd-abi.h
- mtd->backing_dev_info = &mtd_bdi_rw_mappable;
- break;
- case MTD_ROM:
- mtd->backing_dev_info = &mtd_bdi_ro_mappable;
- break;
- default:
- mtd->backing_dev_info = &mtd_bdi_unmappable;
- break;
- }
- }
- BUG_ON(mtd->writesize == 0);
- mutex_lock(&mtd_table_mutex);//给操作mtd_table加锁
- do {
- if (!idr_pre_get(&mtd_idr, GFP_KERNEL))//为mtd_idr分配内存
- goto fail_locked;
- error = idr_get_new(&mtd_idr, mtd, &i);//将id号和mtd_idr关联
- } while (error == -EAGAIN);
- if (error)
- goto fail_locked;
- mtd->index = i;
- mtd->usecount = 0;
- if (is_power_of_2(mtd->erasesize))
- mtd->erasesize_shift = ffs(mtd->erasesize) - 1;
- else
- mtd->erasesize_shift = 0;
- if (is_power_of_2(mtd->writesize))
- mtd->writesize_shift = ffs(mtd->writesize) - 1;
- else
- mtd->writesize_shift = 0;
- mtd->erasesize_mask = (1 << mtd->erasesize_shift) - 1;
- mtd->writesize_mask = (1 << mtd->writesize_shift) - 1;
- /* Some chips always power up locked. Unlock them now */
- if ((mtd->flags & MTD_WRITEABLE)
- && (mtd->flags & MTD_POWERUP_LOCK) && mtd->unlock) {
- if (mtd->unlock(mtd, 0, mtd->size))
- printk(KERN_WARNING
- "%s: unlock failed, writes may not work\n",
- mtd->name);
- }
- /* Caller should have set dev.parent to match the
- * physical device.
- */
- mtd->dev.type = &mtd_devtype;
- mtd->dev.class = &mtd_class;
- mtd->dev.devt = MTD_DEVT(i);
- //设置mtd设备名
- dev_set_name(&mtd->dev, "mtd%d", i);
- //设置mtd设备信息mtd_info
- dev_set_drvdata(&mtd->dev, mtd);
- //注册设备
- if (device_register(&mtd->dev) != 0)
- goto fail_added;
- //创建设备
- if (MTD_DEVT(i))
- device_create(&mtd_class, mtd->dev.parent,
- MTD_DEVT(i) + 1,
- NULL, "mtd%dro", i);
- DEBUG(0, "mtd: Giving out device %d to %s\n", i, mtd->name);
- /* No need to get a refcount on the module containing
- the notifier, since we hold the mtd_table_mutex */
- //遍历list链表将每个mtd_notifier执行add()函数,对新加入的mtd设备操作,通知所有的MTD user新的MTD设备的到来
- list_for_each_entry(not, &mtd_notifiers, list)
- not->add(mtd);
- //解锁信号量
- mutex_unlock(&mtd_table_mutex);
- /* We _know_ we aren't being removed, because
- our caller is still holding us here. So none
- of this try_ nonsense, and no bitching about it
- either. :) */
- __module_get(THIS_MODULE);
- return 0;
- fail_added:
- idr_remove(&mtd_idr, i);
- fail_locked:
- mutex_unlock(&mtd_table_mutex);
- return 1;
- }
其中用到的IDR机制如下:
(1)获得idr
要在代码中使用idr,首先要包括<linux/idr.h>。接下来,我们要在代码中分配idr结构体,并初始化:
void idr_init(struct idr *idp);
其中idr定义如下:
struct idr {
struct idr_layer *top;
struct idr_layer *id_free;
int layers;
int id_free_cnt;
spinlock_t lock;
};
/* idr是idr机制的核心结构体 */
(2)为idr分配内存
int idr_pre_get(struct idr *idp, unsigned int gfp_mask);
每次通过idr获得ID号之前,需要先分配内存。
返回0表示错误,非零值代表正常
(3)分配ID号并将ID号和指针关联
int idr_get_new(struct idr *idp, void *ptr, int *id);
int idr_get_new_above(struct idr *idp, void *ptr, int start_id, int *id);
idp: 之前通过idr_init初始化的idr指针
id: 由内核自动分配的ID号
ptr: 和ID号相关联的指针
start_id: 起始ID号。内核在分配ID号时,会从start_id开始。如果为I2C节点分配ID号,可以将设备地址作为start_id
函数调用正常返回0,如果没有ID可以分配,则返回-ENOSPC
在实际中,上述函数常常采用如下方式使用:
again:
if (idr_pre_get(&my_idr, GFP_KERNEL) == 0) {
/* No memory, give up entirely */
}
spin_lock(&my_lock);
result = idr_get_new(&my_idr, &target, &id);
if (result == -EAGAIN) {
sigh();
spin_unlock(&my_lock);
goto again;
}
(4)通过ID号搜索对应的指针
void *idr_find(struct idr *idp, int id);
返回值是和给定id相关联的指针,如果没有,则返回NULL
(5)删除ID
要删除一个ID,使用:
void idr_remove(struct idr *idp, int id);
通过上面这些方法,内核代码可以为子设备,inode生成对应的ID号。这些函数都定义在lib/idr.c中
- /**
- * del_mtd_device - unregister an MTD device
- * @mtd: pointer to MTD device info structure
- *
- * Remove a device from the list of MTD devices present in the system,
- * and notify each currently active MTD 'user' of its departure.
- * Returns zero on success or 1 on failure, which currently will happen
- * if the requested device does not appear to be present in the list.
- */
- //删除mtd设备函数。
- //从MTD设备的链表中移除该MTD设备信息,并通知系统中所有的MTD user该MTD设备的移除。
- //返回0表示成功,返回1表示出错(该设备信息不存在设备链表中)
- int del_mtd_device (struct mtd_info *mtd)
- {
- int ret;
- struct mtd_notifier *not;//定义一个mtd_notifier指针
- mutex_lock(&mtd_table_mutex);
- if (idr_find(&mtd_idr, mtd->index) != mtd) {
- ret = -ENODEV;
- goto out_error;
- }
- /* No need to get a refcount on the module containing
- the notifier, since we hold the mtd_table_mutex */
- //遍历list链表,并使每个mtd_notifier执行remove函数,通知每个MTD user该设备的移除
- list_for_each_entry(not, &mtd_notifiers, list)
- not->remove(mtd);
- if (mtd->usecount) {
- printk(KERN_NOTICE "Removing MTD device #%d (%s) with use count %d\n",
- mtd->index, mtd->name, mtd->usecount);
- ret = -EBUSY;
- } else {
- device_unregister(&mtd->dev);//移除MTD设备
- idr_remove(&mtd_idr, mtd->index);//移除mtd的id号并释放已分配的内存
- module_put(THIS_MODULE);
- ret = 0;
- }
- out_error:
- mutex_unlock(&mtd_table_mutex);
- return ret;
- }
4、register_mtd_user函数
- /**
- * register_mtd_user - register a 'user' of MTD devices.
- * @new: pointer to notifier info structure
- *
- * Registers a pair of callbacks function to be called upon addition
- * or removal of MTD devices. Causes the 'add' callback to be immediately
- * invoked for each MTD device currently present in the system.
- */
- //MTD原始设备使用者注册MTD设备(具体的字符设备或块设备)
- //参数是新的mtd通知器,将其加入mtd_notifiers队列,然后
- void register_mtd_user (struct mtd_notifier *new)
- {
- struct mtd_info *mtd;
- mutex_lock(&mtd_table_mutex);
- //将new->list头插mtd_notifiers入链表
- list_add(&new->list, &mtd_notifiers);
- __module_get(THIS_MODULE);
- //对每个MTD原始设备执行add函数
- mtd_for_each_device(mtd)
- new->add(mtd);
- mutex_unlock(&mtd_table_mutex);
- }
5、unregister_mtd_user函数
- /**
- * unregister_mtd_user - unregister a 'user' of MTD devices.
- * @old: pointer to notifier info structure
- *
- * Removes a callback function pair from the list of 'users' to be
- * notified upon addition or removal of MTD devices. Causes the
- * 'remove' callback to be immediately invoked for each MTD device
- * currently present in the system.
- */
- //删除MTD设备。
- //通知所有该MTD原始设备的MTD设备执行remove()函数,将被删除的MTD设备的通知器从mtd_notifier队列中删除
- int unregister_mtd_user (struct mtd_notifier *old)
- {
- struct mtd_info *mtd;
- mutex_lock(&mtd_table_mutex);
- module_put(THIS_MODULE);
- //通知所有该MTD原始设备的MTD设备执行remove()函数
- mtd_for_each_device(mtd)
- old->remove(mtd);
- //将被删除的MTD设备的通知器从mtd_notifier队列中删除
- list_del(&old->list);
- mutex_unlock(&mtd_table_mutex);
- return 0;
- }
6、获取MTD设备的操作指针,只是参数不同,一个是按照设备地址,另一个是安装设备的名称来获取MTD设备的操作地址
struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
struct mtd_info *get_mtd_device_nm(const char *name)
下面现分析第一个函数
- /**
- * get_mtd_device - obtain a validated handle for an MTD device
- * @mtd: last known address of the required MTD device
- * @num: internal device number of the required MTD device
- *
- * Given a number and NULL address, return the num'th entry in the device
- * table, if any. Given an address and num == -1, search the device table
- * for a device with that address and return if it's still present. Given
- * both, return the num'th driver only if its address matches. Return
- * error code if not.
- */
- //根据设备地址来获取MTD设备的操作地址
- struct mtd_info *get_mtd_device(struct mtd_info *mtd, int num)
- {
- struct mtd_info *ret = NULL, *other;
- int err = -ENODEV;
- //给mtd_table加锁,以便互斥访问
- mutex_lock(&mtd_table_mutex);
- if (num == -1) {//num=-1&&链表不空,则返回mtd的地址
- mtd_for_each_device(other) {
- if (other == mtd) {
- ret = mtd;
- break;
- }
- }
- } else if (num >= 0) {//num>=0,查找第num个设备,若不空,返回地址,若为空,返回NULL
- ret = idr_find(&mtd_idr, num);
- if (mtd && mtd != ret)
- ret = NULL;
- }
- if (!ret) {
- ret = ERR_PTR(err);
- goto out;
- }
- err = __get_mtd_device(ret);
- //错误处理
- if (err)
- ret = ERR_PTR(err);
- out:
- mutex_unlock(&mtd_table_mutex);//解锁互斥信号量
- return ret;
- }
- int __get_mtd_device(struct mtd_info *mtd)
- {
- int err;
- if (!try_module_get(mtd->owner))
- return -ENODEV;
- if (mtd->get_device) {
- err = mtd->get_device(mtd);
- if (err) {
- module_put(mtd->owner);
- return err;
- }
- }
- mtd->usecount++;//增加该MTD原始设备的使用者计数器
- return 0;
- }
第二个函数
- /**
- * get_mtd_device_nm - obtain a validated handle for an MTD device by
- * device name
- * @name: MTD device name to open
- *
- * This function returns MTD device description structure in case of
- * success and an error code in case of failure.
- */
- //通过设备名来获得相应的MTD原始设备的操作地址
- //该函数和上面的函数类似,不过就是通过循环比较MTD设备的name字段来返回
- struct mtd_info *get_mtd_device_nm(const char *name)
- {
- int err = -ENODEV;
- struct mtd_info *mtd = NULL, *other;
- mutex_lock(&mtd_table_mutex);
- mtd_for_each_device(other) {
- if (!strcmp(name, other->name)) {
- mtd = other;
- break;
- }
- }
- if (!mtd)
- goto out_unlock;
- if (!try_module_get(mtd->owner))
- goto out_unlock;
- if (mtd->get_device) {
- err = mtd->get_device(mtd);
- if (err)
- goto out_put;
- }
- mtd->usecount++;
- mutex_unlock(&mtd_table_mutex);
- return mtd;
- out_put:
- module_put(mtd->owner);
- out_unlock:
- mutex_unlock(&mtd_table_mutex);
- return ERR_PTR(err);
- }
下篇分析MTD原始设备的分区实现方法ARM-Linux驱动--MTD驱动分析(三)
- ARM-Linux驱动--MTD驱动分析(二)
- ARM-Linux驱动--MTD驱动分析(二)
- ARM-Linux驱动--MTD驱动分析(一)
- ARM-Linux驱动--MTD驱动分析(三)
- ARM-Linux驱动--MTD驱动分析(三)
- ARM-Linux驱动--MTD驱动分析(一)
- ARM-Linux驱动--MTD驱动分析(一)
- ARM-Linux驱动--MTD驱动分析(一)
- ARM-Linux驱动--MTD驱动分析(三)
- ARM-Linux驱动--DM9000网卡驱动分析(二)
- ARM-Linux驱动--DM9000网卡驱动分析(二)
- ARM-Linux驱动--DM9000网卡驱动分析(二)
- ARM-Linux驱动--DM9000网卡驱动分析(二)
- Linux 2.6.11 MTD驱动情景分析
- Linux 2.6.11 MTD驱动情景分析
- Linux 2.6.11 MTD驱动情景分析
- LINUX 2.6.11 MTD驱动情景分析
- mtd子系统驱动分析
- Android 中全屏或者取消标题栏
- 新年新开始
- visio 怎么画直线
- SQL语句使用经典例子
- Jetty实战之 嵌入式运行Jetty多Connector
- ARM-Linux驱动--MTD驱动分析(二)
- Stream与String转换
- ARM-Linux驱动--MTD驱动分析(三)
- ARM-Linux驱动--MTD驱动分析(一)
- 硬盘接口线类型引起的系统蓝屏问题
- linux内核移植-移植2.6.35.4内核到s3c2440
- [置顶]Linux 内核学习(1)
- 轻装上阵拥抱明天—写在龙年开工的第一天
- 为什么我们苦逼的程序员难晋升