ARM-Linux驱动--MTD驱动分析(三)

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.youkuaiyun.com/yming0221/article/details/7207908

*接上文ARM-Linux驱动--MTD驱动分析(二)

本文分析MTD设备的分区管理机制

分区管理实际上是将一个MTD设备分成几个分区，将其作为单独的MTD原始设备进行管理。

1、分区的结构体描述结构体mtd_part

/* Our partition node structure */
//分区结构信息
struct mtd_part {
	struct mtd_info mtd;//mtd_info数据结构，会被加入mtd_table中
	struct mtd_info *master;//该分区的主分区
	uint64_t offset;//该分区的偏移地址
	struct list_head list;
};

2、分区链表mtd_partitions

/* Our partition linked list */
//声明mtd_partitions链表
static LIST_HEAD(mtd_partitions);

3、add_mtd_partitions函数

/*
 * This function, given a master MTD object and a partition table, creates
 * and registers slave MTD objects which are bound to the master according to
 * the partition definitions.
 *
 * We don't register the master, or expect the caller to have done so,
 * for reasons of data integrity.
 */
//根据一个MTD主设备和分区表，创建新的主设备下的副设备并记录到分区表中
//这里我们不将注射被注册到分区表中，只注册副设备到到分区表中
int add_mtd_partitions(struct mtd_info *master,
		       const struct mtd_partition *parts,
		       int nbparts)
{
	struct mtd_part *slave;
	uint64_t cur_offset = 0;
	int i;

	printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);

	for (i = 0; i < nbparts; i++) {//对每一个分区调用add_one_partition函数更新分区表
		slave = add_one_partition(master, parts + i, i, cur_offset);
		if (!slave)
			return -ENOMEM;
		cur_offset = slave->offset + slave->mtd.size;
	}

	return 0;
}
EXPORT_SYMBOL(add_mtd_partitions);

而add_one_partition函数实现如下：

//创建一个分区
static struct mtd_part *add_one_partition(struct mtd_info *master,
		const struct mtd_partition *part, int partno,
		uint64_t cur_offset)
{
	struct mtd_part *slave;

	/* allocate the partition structure */
	slave = kzalloc(sizeof(*slave), GFP_KERNEL);//分配内存
	if (!slave) {
		printk(KERN_ERR"memory allocation error while creating partitions for \"%s\"\n",
			master->name);
		del_mtd_partitions(master);
		return NULL;
	}
	list_add(&slave->list, &mtd_partitions);//将原始设备表添加到分区表中

	/* set up the MTD object for this partition */
	//大部分根据master相应的信息设置MTD分区slave的信息
	slave->mtd.type = master->type;
	slave->mtd.flags = master->flags & ~part->mask_flags;
	slave->mtd.size = part->size;
	slave->mtd.writesize = master->writesize;
	slave->mtd.oobsize = master->oobsize;
	slave->mtd.oobavail = master->oobavail;
	slave->mtd.subpage_sft = master->subpage_sft;

	slave->mtd.name = part->name;
	slave->mtd.owner = master->owner;
	slave->mtd.backing_dev_info = master->backing_dev_info;

	/* NOTE:  we don't arrange MTDs as a tree; it'd be error-prone
	 * to have the same data be in two different partitions.
	 */
	slave->mtd.dev.parent = master->dev.parent;

	slave->mtd.read = part_read;
	slave->mtd.write = part_write;

	if (master->panic_write)
		slave->mtd.panic_write = part_panic_write;

	if (master->point && master->unpoint) {
		slave->mtd.point = part_point;
		slave->mtd.unpoint = part_unpoint;
	}

	if (master->get_unmapped_area)
		slave->mtd.get_unmapped_area = part_get_unmapped_area;
	if (master->read_oob)
		slave->mtd.read_oob = part_read_oob;
	if (master->write_oob)
		slave->mtd.write_oob = part_write_oob;
	if (master->read_user_prot_reg)
		slave->mtd.read_user_prot_reg = part_read_user_prot_reg;
	if (master->read_fact_prot_reg)
		slave->mtd.read_fact_prot_reg = part_read_fact_prot_reg;
	if (master->write_user_prot_reg)
		slave->mtd.write_user_prot_reg = part_write_user_prot_reg;
	if (master->lock_user_prot_reg)
		slave->mtd.lock_user_prot_reg = part_lock_user_prot_reg;
	if (master->get_user_prot_info)
		slave->mtd.get_user_prot_info = part_get_user_prot_info;
	if (master->get_fact_prot_info)
		slave->mtd.get_fact_prot_info = part_get_fact_prot_info;
	if (master->sync)
		slave->mtd.sync = part_sync;
	if (!partno && !master->dev.class && master->suspend && master->resume) {
			slave->mtd.suspend = part_suspend;
			slave->mtd.resume = part_resume;
	}
	if (master->writev)
		slave->mtd.writev = part_writev;
	if (master->lock)
		slave->mtd.lock = part_lock;
	if (master->unlock)
		slave->mtd.unlock = part_unlock;
	if (master->block_isbad)
		slave->mtd.block_isbad = part_block_isbad;
	if (master->block_markbad)
		slave->mtd.block_markbad = part_block_markbad;
	slave->mtd.erase = part_erase;
	slave->master = master;
	slave->offset = part->offset;

	if (slave->offset == MTDPART_OFS_APPEND)
		slave->offset = cur_offset;
	if (slave->offset == MTDPART_OFS_NXTBLK) {
		slave->offset = cur_offset;
		if (mtd_mod_by_eb(cur_offset, master) != 0) {
			/* Round up to next erasesize */
			slave->offset = (mtd_div_by_eb(cur_offset, master) + 1) * master->erasesize;
			printk(KERN_NOTICE "Moving partition %d: "
			       "0x%012llx -> 0x%012llx\n", partno,
			       (unsigned long long)cur_offset, (unsigned long long)slave->offset);
		}
	}
	if (slave->mtd.size == MTDPART_SIZ_FULL)
		slave->mtd.size = master->size - slave->offset;

	printk(KERN_NOTICE "0x%012llx-0x%012llx : \"%s\"\n", (unsigned long long)slave->offset,
		(unsigned long long)(slave->offset + slave->mtd.size), slave->mtd.name);

	/* let's do some sanity checks */
	if (slave->offset >= master->size) {
		/* let's register it anyway to preserve ordering */
		slave->offset = 0;
		slave->mtd.size = 0;
		printk(KERN_ERR"mtd: partition \"%s\" is out of reach -- disabled\n",
			part->name);
		goto out_register;
	}
	if (slave->offset + slave->mtd.size > master->size) {
		slave->mtd.size = master->size - slave->offset;
		printk(KERN_WARNING"mtd: partition \"%s\" extends beyond the end of device \"%s\" -- size truncated to %#llx\n",
			part->name, master->name, (unsigned long long)slave->mtd.size);
	}
	if (master->numeraseregions > 1) {
		/* Deal with variable erase size stuff */
		int i, max = master->numeraseregions;
		u64 end = slave->offset + slave->mtd.size;
		struct mtd_erase_region_info *regions = master->eraseregions;

		/* Find the first erase regions which is part of this
		 * partition. */
		for (i = 0; i < max && regions[i].offset <= slave->offset; i++)
			;
		/* The loop searched for the region _behind_ the first one */
		if (i > 0)
			i--;

		/* Pick biggest erasesize */
		for (; i < max && regions[i].offset < end; i++) {
			if (slave->mtd.erasesize < regions[i].erasesize) {
				slave->mtd.erasesize = regions[i].erasesize;
			}
		}
		BUG_ON(slave->mtd.erasesize == 0);
	} else {
		/* Single erase size */
		slave->mtd.erasesize = master->erasesize;
	}

	if ((slave->mtd.flags & MTD_WRITEABLE) &&
	    mtd_mod_by_eb(slave->offset, &slave->mtd)) {
		/* Doesn't start on a boundary of major erase size */
		/* FIXME: Let it be writable if it is on a boundary of
		 * _minor_ erase size though */
		slave->mtd.flags &= ~MTD_WRITEABLE;
		printk(KERN_WARNING"mtd: partition \"%s\" doesn't start on an erase block boundary -- force read-only\n",
			part->name);
	}
	if ((slave->mtd.flags & MTD_WRITEABLE) &&
	    mtd_mod_by_eb(slave->mtd.size, &slave->mtd)) {
		slave->mtd.flags &= ~MTD_WRITEABLE;
		printk(KERN_WARNING"mtd: partition \"%s\" doesn't end on an erase block -- force read-only\n",
			part->name);
	}

	slave->mtd.ecclayout = master->ecclayout;
	if (master->block_isbad) {
		uint64_t offs = 0;

		while (offs < slave->mtd.size) {
			if (master->block_isbad(master,
						offs + slave->offset))
				slave->mtd.ecc_stats.badblocks++;
			offs += slave->mtd.erasesize;
		}
	}

out_register:
	/* register our partition */
	//最后调用add_mtd_device根据该设备的mtd_info信息添加设备链表，将其作为一个独立的MTD原始设备
	add_mtd_device(&slave->mtd);

	return slave;
}

4、del_mtd_partition函数

/*
 * This function unregisters and destroy all slave MTD objects which are
 * attached to the given master MTD object.
 */
//将一个主设备下的所有副设备删除
int del_mtd_partitions(struct mtd_info *master)
{
	struct mtd_part *slave, *next;

	list_for_each_entry_safe(slave, next, &mtd_partitions, list)//遍历mtd_partitions链表，查找到指定的主设备
		if (slave->master == master) {
			list_del(&slave->list);//将主设备下的附属设备删除
			del_mtd_device(&slave->mtd);//调用del_mtd_device函数将每个设备从MTD原始设备表中删除
			kfree(slave);//释放内存
		}

	return 0;
}
EXPORT_SYMBOL(del_mtd_partitions);

5、其他的分区管理函数

/*
 * MTD methods which simply translate the effective address and pass through
 * to the _real_ device.
 */
//读取某个分区的指定数据
static int part_read(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	struct mtd_ecc_stats stats;
	int res;

	stats = part->master->ecc_stats;

	if (from >= mtd->size)
		len = 0;
	else if (from + len > mtd->size)
		len = mtd->size - from;
	res = part->master->read(part->master, from + part->offset,
				   len, retlen, buf);
	if (unlikely(res)) {
		if (res == -EUCLEAN)
			mtd->ecc_stats.corrected += part->master->ecc_stats.corrected - stats.corrected;
		if (res == -EBADMSG)
			mtd->ecc_stats.failed += part->master->ecc_stats.failed - stats.failed;
	}
	return res;
}

static int part_point(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, void **virt, resource_size_t *phys)
{
	struct mtd_part *part = PART(mtd);
	if (from >= mtd->size)
		len = 0;
	else if (from + len > mtd->size)
		len = mtd->size - from;
	return part->master->point (part->master, from + part->offset,
				    len, retlen, virt, phys);
}

static void part_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
{
	struct mtd_part *part = PART(mtd);

	part->master->unpoint(part->master, from + part->offset, len);
}
//获取空闲的内存驱动
static unsigned long part_get_unmapped_area(struct mtd_info *mtd,
					    unsigned long len,
					    unsigned long offset,
					    unsigned long flags)
{
	struct mtd_part *part = PART(mtd);

	offset += part->offset;
	return part->master->get_unmapped_area(part->master, len, offset,
					       flags);
}

static int part_read_oob(struct mtd_info *mtd, loff_t from,
		struct mtd_oob_ops *ops)
{
	struct mtd_part *part = PART(mtd);
	int res;

	if (from >= mtd->size)
		return -EINVAL;
	if (ops->datbuf && from + ops->len > mtd->size)
		return -EINVAL;
	res = part->master->read_oob(part->master, from + part->offset, ops);

	if (unlikely(res)) {
		if (res == -EUCLEAN)
			mtd->ecc_stats.corrected++;
		if (res == -EBADMSG)
			mtd->ecc_stats.failed++;
	}
	return res;
}

static int part_read_user_prot_reg(struct mtd_info *mtd, loff_t from,
		size_t len, size_t *retlen, u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	return part->master->read_user_prot_reg(part->master, from,
					len, retlen, buf);
}

static int part_get_user_prot_info(struct mtd_info *mtd,
		struct otp_info *buf, size_t len)
{
	struct mtd_part *part = PART(mtd);
	return part->master->get_user_prot_info(part->master, buf, len);
}

static int part_read_fact_prot_reg(struct mtd_info *mtd, loff_t from,
		size_t len, size_t *retlen, u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	return part->master->read_fact_prot_reg(part->master, from,
					len, retlen, buf);
}

static int part_get_fact_prot_info(struct mtd_info *mtd, struct otp_info *buf,
		size_t len)
{
	struct mtd_part *part = PART(mtd);
	return part->master->get_fact_prot_info(part->master, buf, len);
}
//分区写函数
static int part_write(struct mtd_info *mtd, loff_t to, size_t len,
		size_t *retlen, const u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;
	if (to >= mtd->size)
		len = 0;
	else if (to + len > mtd->size)
		len = mtd->size - to;
	return part->master->write(part->master, to + part->offset,
				    len, retlen, buf);
}

static int part_panic_write(struct mtd_info *mtd, loff_t to, size_t len,
		size_t *retlen, const u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;
	if (to >= mtd->size)
		len = 0;
	else if (to + len > mtd->size)
		len = mtd->size - to;
	return part->master->panic_write(part->master, to + part->offset,
				    len, retlen, buf);
}

static int part_write_oob(struct mtd_info *mtd, loff_t to,
		struct mtd_oob_ops *ops)
{
	struct mtd_part *part = PART(mtd);

	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;

	if (to >= mtd->size)
		return -EINVAL;
	if (ops->datbuf && to + ops->len > mtd->size)
		return -EINVAL;
	return part->master->write_oob(part->master, to + part->offset, ops);
}

static int part_write_user_prot_reg(struct mtd_info *mtd, loff_t from,
		size_t len, size_t *retlen, u_char *buf)
{
	struct mtd_part *part = PART(mtd);
	return part->master->write_user_prot_reg(part->master, from,
					len, retlen, buf);
}

static int part_lock_user_prot_reg(struct mtd_info *mtd, loff_t from,
		size_t len)
{
	struct mtd_part *part = PART(mtd);
	return part->master->lock_user_prot_reg(part->master, from, len);
}

static int part_writev(struct mtd_info *mtd, const struct kvec *vecs,
		unsigned long count, loff_t to, size_t *retlen)
{
	struct mtd_part *part = PART(mtd);
	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;
	return part->master->writev(part->master, vecs, count,
					to + part->offset, retlen);
}

static int part_erase(struct mtd_info *mtd, struct erase_info *instr)
{
	struct mtd_part *part = PART(mtd);
	int ret;
	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;
	if (instr->addr >= mtd->size)
		return -EINVAL;
	instr->addr += part->offset;
	ret = part->master->erase(part->master, instr);
	if (ret) {
		if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
			instr->fail_addr -= part->offset;
		instr->addr -= part->offset;
	}
	return ret;
}

void mtd_erase_callback(struct erase_info *instr)
{
	if (instr->mtd->erase == part_erase) {
		struct mtd_part *part = PART(instr->mtd);

		if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
			instr->fail_addr -= part->offset;
		instr->addr -= part->offset;
	}
	if (instr->callback)
		instr->callback(instr);
}
EXPORT_SYMBOL_GPL(mtd_erase_callback);

static int part_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
	struct mtd_part *part = PART(mtd);
	if ((len + ofs) > mtd->size)
		return -EINVAL;
	return part->master->lock(part->master, ofs + part->offset, len);
}

static int part_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
{
	struct mtd_part *part = PART(mtd);
	if ((len + ofs) > mtd->size)
		return -EINVAL;
	return part->master->unlock(part->master, ofs + part->offset, len);
}
//分区同步函数
static void part_sync(struct mtd_info *mtd)
{
	struct mtd_part *part = PART(mtd);
	part->master->sync(part->master);
}
//支持电源管理的功能函数
static int part_suspend(struct mtd_info *mtd)
{
	struct mtd_part *part = PART(mtd);
	return part->master->suspend(part->master);
}

static void part_resume(struct mtd_info *mtd)
{
	struct mtd_part *part = PART(mtd);
	part->master->resume(part->master);
}

static int part_block_isbad(struct mtd_info *mtd, loff_t ofs)
{
	struct mtd_part *part = PART(mtd);
	if (ofs >= mtd->size)
		return -EINVAL;
	ofs += part->offset;
	return part->master->block_isbad(part->master, ofs);
}
//标记设备地址坏块
static int part_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
	struct mtd_part *part = PART(mtd);
	int res;

	if (!(mtd->flags & MTD_WRITEABLE))
		return -EROFS;
	if (ofs >= mtd->size)
		return -EINVAL;
	ofs += part->offset;
	res = part->master->block_markbad(part->master, ofs);
	if (!res)
		mtd->ecc_stats.badblocks++;
	return res;
}

下篇分析具体的MTD设备，字符设备和块设备，待续........