5、MTD原始设备与FLASH硬件驱动的对话 (一) .

发布时间：2020-12-15 18:01:47 所属栏目：百科来源：网络整理

导读：看了Linux MTD源代码分析后对以MTD的分层结构以及各层的分工情况有了大致的了解，然而各层之间是如何进行对话的呢，对于这个问题，Linux MTD源代码分析上没有详细的去说明。小弟抽空研究了一下，打算从下到上，在从上到下，分两条主线来研究一下MTD原始设备

看了<<Linux MTD源代码分析>>后对以MTD的分层结构以及各层的分工情况有了大致的了解，然而各层之间是如何进行对话的呢，对于这个问题，<<Linux MTD源代码分析>>上没有详细的去说明。

小弟抽空研究了一下，打算从下到上，在从上到下，分两条主线来研究一下MTD原始设备与FLASH硬件驱动的对话(MTD原始设备与更上层的对话留待以后再研究)。

以下是第一部分，从下到上的介绍FLASH硬件驱动与MTD原始设备是如何建立联系的。

1、首先从入口函数开始：
static int s3c24xx_nand_probe(struct device *dev,int is_s3c2440)
{
??? struct platform_device *pdev = to_platform_device(dev);
??? struct s3c2410_platform_nand *plat = to_nand_plat(dev);
??? //获取nand flash配置用结构体数据(dev.c中定义，详细见附录部分)
??? struct s3c2410_nand_info *info;
??? struct s3c2410_nand_mtd *nmtd;
??? struct s3c2410_nand_set *sets;
??? struct resource *res;
??? int err = 0;
??? int size;
??? int nr_sets;
??? int setno;

??? pr_debug("s3c2410_nand_probe(%p)/n",dev);

??? info = kmalloc(sizeof(*info),GFP_KERNEL);
??? if (info == NULL) {
??? ??? printk(KERN_ERR PFX "no memory for flash info/n");
??? ??? err = -ENOMEM;
??? ??? goto exit_error;
??? }

??? memzero(info,sizeof(*info));
??? dev_set_drvdata(dev,info);?? ?? ?? ?? ?? ?? //以后有用

??? spin_lock_init(&info->controller.lock);?? ?? //初始化自旋锁
??? init_waitqueue_head(&info->controller.wq);?? //初始化等待队列

??? /* get the clock source and enable it */

??? info->clk = clk_get(dev,"nand");
??? if (IS_ERR(info->clk)) {
??? ??? printk(KERN_ERR PFX "failed to get clock");
??? ??? err = -ENOENT;
??? ??? goto exit_error;
??? }

??? clk_use(info->clk);
??? clk_enable(info->clk);

??? /* allocate and map the resource */

??? /* currently we assume we have the one resource */
??? res? = pdev->resource;?? ?? ?? ?? ?? ?? ?? ?? //提取dev.c中定义的与设备相关的资源
??? size = res->end - res->start + 1;

??? info->area = request_mem_region(res->start,size,pdev->name);

??? if (info->area == NULL) {
??? ??? printk(KERN_ERR PFX "cannot reserve register region/n");
??? ??? err = -ENOENT;
??? ??? goto exit_error;
??? }

??? info->device???? = dev;
??? info->platform?? = plat;?? ?? ?? ?? ?? ?? ?? //保存好struct s3c2410_platform_nand结构数据
??? info->regs?????? = ioremap(res->start,size);//映射nand flash用到的寄存器
??? info->is_s3c2440 = is_s3c2440;?? ?? ?? ?? ??

??? if (info->regs == NULL) {
??? ??? printk(KERN_ERR PFX "cannot reserve register region/n");
??? ??? err = -EIO;
??? ??? goto exit_error;
??? }??? ???

??? printk(KERN_INFO PFX "mapped registers at %p/n",info->regs);

??? /* initialise the hardware */

??? err = s3c2410_nand_inithw(info,dev);
??? //初始化s3c2410 nand flash控制，主要是配置S3C2410_NFCONF寄存器
??? if (err != 0)
??? ??? goto exit_error;

??? sets = (plat != NULL) ? plat->sets : NULL;??
??? nr_sets = (plat != NULL) ? plat->nr_sets : 1;
??
??? info->mtd_count = nr_sets;
??? //我的板上只有一块nand flash，配置信息见plat-sets，数目为1。

??? /* allocate our information */

??? size = nr_sets * sizeof(*info->mtds);
??? info->mtds = kmalloc(size,GFP_KERNEL);
??? if (info->mtds == NULL) {
??? ??? printk(KERN_ERR PFX "failed to allocate mtd storage/n");
??? ??? err = -ENOMEM;
??? ??? goto exit_error;
??? }

??? memzero(info->mtds,size);

??? /* initialise all possible chips */

??? nmtd = info->mtds;

??? for (setno = 0; setno < nr_sets; setno++,nmtd++) {
??? ??? pr_debug("initialising set %d (%p,info %p)/n",
??? ??? ??? ?setno,nmtd,info);
??? ???
??? ??? s3c2410_nand_init_chip(info,sets);

??? ??? nmtd->scan_res = nand_scan(&nmtd->mtd,
??? ??? ??? ??? ??? ?? (sets) ? sets->nr_chips : 1);//为什么使用set->nr_chips(还没配置的东西)？

??? ??? if (nmtd->scan_res == 0) {
??? ??? ??? s3c2410_nand_add_partition(info,sets);
??? ??? }

??? ??? if (sets != NULL)
??? ??? ??? sets++;
??? }
???
??? pr_debug("initialised ok/n");
??? return 0;

?exit_error:
??? s3c2410_nand_remove(dev);

??? if (err == 0)
??? ??? err = -EINVAL;
??? return err;
}

//初始化代表一片flash的struct nand_chip结构

static void s3c2410_nand_init_chip(struct s3c2410_nand_info *info,
??? ??? ??? ??? ?? struct s3c2410_nand_mtd *nmtd,
??? ??? ??? ??? ?? struct s3c2410_nand_set *set)
{
??? struct nand_chip *chip = &nmtd->chip;

??? chip->IO_ADDR_R??? ?? = info->regs + S3C2410_NFDATA;?? //读地址
??? chip->IO_ADDR_W??? = info->regs + S3C2410_NFDATA;?? ?? //写地址
??? chip->hwcontrol??? = s3c2410_nand_hwcontrol;??
??? chip->dev_ready??? = s3c2410_nand_devready;?? ?? ?? ?? //ready状态查询
??? chip->write_buf??? = s3c2410_nand_write_buf;?? ?? ?? ? //写函数
??? chip->read_buf???? = s3c2410_nand_read_buf;?? ?? ?? ?? //读函数
??? chip->select_chip? = s3c2410_nand_select_chip;?? ?? ?? //片选函数
??? chip->chip_delay?? = 50;
??? chip->priv??? ?? = nmtd;
??? chip->options??? ?? = 0;
??? chip->controller?? = &info->controller;

??? if (info->is_s3c2440) {
??? ??? chip->IO_ADDR_R??? ?= info->regs + S3C2440_NFDATA;
??? ??? chip->IO_ADDR_W? = info->regs + S3C2440_NFDATA;
??? ??? chip->hwcontrol? = s3c2440_nand_hwcontrol;
??? }

??? nmtd->info??? ?? = info;
??? nmtd->mtd.priv??? ?? = chip;?? ?? ?? ??
??? //nand_scan函数中会调用struct nand_chip *this = mtd->priv取出该struct nand_chip结构
??? nmtd->set??? ?? = set;

??? if (hardware_ecc) {
??? ??? chip->correct_data? = s3c2410_nand_correct_data;
??? ??? chip->enable_hwecc? = s3c2410_nand_enable_hwecc;
??? ??? chip->calculate_ecc = s3c2410_nand_calculate_ecc;
??? ??? chip->eccmode??? ??? = NAND_ECC_HW3_512;
??? ??? chip->autooob?????? = &nand_hw_eccoob;

??? ??? if (info->is_s3c2440) {
??? ??? ??? chip->enable_hwecc? = s3c2440_nand_enable_hwecc;
??? ??? ??? chip->calculate_ecc = s3c2440_nand_calculate_ecc;
??? ??? }
??? } else {?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ??
??? ??? chip->eccmode??? ??? = NAND_ECC_SOFT;?? ?? ?? //ECC的类型
??????? }
}

/* command and control functions
?*
?* Note,these all use tglx's method of changing the IO_ADDR_W field
?* to make the code simpler,and use the nand layer's code to issue the
?* command and address sequences via the proper IO ports.
?*
*/

static void s3c2410_nand_hwcontrol(struct mtd_info *mtd,int cmd)
{
??? struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
??? struct nand_chip *chip = mtd->priv;

??? switch (cmd) {
??? case NAND_CTL_SETNCE:
??? case NAND_CTL_CLRNCE:
??? ??? printk(KERN_ERR "%s: called for NCE/n",__FUNCTION__);
??? ??? break;

??? case NAND_CTL_SETCLE:
??? ??? chip->IO_ADDR_W = info->regs + S3C2410_NFCMD;//写命令
??? ??? break;

??? case NAND_CTL_SETALE:
??? ??? chip->IO_ADDR_W = info->regs + S3C2410_NFADDR;//写地址
??? ??? break;

??? ??? /* NAND_CTL_CLRCLE: */
??? ??? /* NAND_CTL_CLRALE: */
??? default:
??? ??? chip->IO_ADDR_W = info->regs + S3C2410_NFDATA;//写数据
??? ??? break;
??? }
}

/* s3c2410_nand_devready()
?*
?* returns 0 if the nand is busy,1 if it is ready
*/

static int s3c2410_nand_devready(struct mtd_info *mtd)
{
??? struct s3c2410_nand_info *info = s3c2410_nand_mtd_toinfo(mtd);
???
??? if (info->is_s3c2440)
??? ??? return readb(info->regs + S3C2440_NFSTAT) & S3C2440_NFSTAT_READY;
??? return readb(info->regs + S3C2410_NFSTAT) & S3C2410_NFSTAT_BUSY;//返回nand flash都忙标志
}

static void s3c2410_nand_write_buf(struct mtd_info *mtd,
??? ??? ??? ??? ?? const u_char *buf,int len)
{
??? struct nand_chip *this = mtd->priv;
??? writesb(this->IO_ADDR_W,buf,len);//写操作
}

static void s3c2410_nand_read_buf(struct mtd_info *mtd,u_char *buf,int len)
{
??? struct nand_chip *this = mtd->priv;
??? readsb(this->IO_ADDR_R,len);//读操作
}

/* select chip */
/*
?* 根据chip都值设置nand flash都片选信号:
?* chip = -1 -- 禁用nand flash
?* chip !=-1 -- 选择对应的nand flash
?*/
static void s3c2410_nand_select_chip(struct mtd_info *mtd,int chip)
{
??? struct s3c2410_nand_info *info;
??? struct s3c2410_nand_mtd *nmtd;
??? struct nand_chip *this = mtd->priv;
??? void __iomem *reg;
??? unsigned long cur;
??? unsigned long bit;

??? nmtd = this->priv;
??? info = nmtd->info;

??? bit = (info->is_s3c2440) ? S3C2440_NFCONT_nFCE : S3C2410_NFCONF_nFCE;
??? reg = info->regs+((info->is_s3c2440) ? S3C2440_NFCONT:S3C2410_NFCONF);

??? cur = readl(reg);

??? if (chip == -1) {
??? ??? cur |= bit;
??? } else {
??? ??? if (nmtd->set != NULL && chip > nmtd->set->nr_chips) {
??? ??? ??? printk(KERN_ERR PFX "chip %d out of range/n",chip);
??? ??? ??? return;
??? ??? }

??? ??? if (info->platform != NULL) {
??? ??? ??? if (info->platform->select_chip != NULL)
??? ??? ??? ??? (info->platform->select_chip)(nmtd->set,chip);
??? ??? }

??? ??? cur &= ~bit;
??? }

??? writel(cur,reg);
}

注：
??? s3c2410_nand_init_chip填充struct nand_chip的一部分成员，nand_scan以通用nand flash的标准进行检测，并填充struct nand_chip的其它成员，必要时根据检测结果进行取舍。

int nand_scan (struct mtd_info *mtd,int maxchips)
{
??? int i,nand_maf_id,nand_dev_id,busw,maf_id;
??? struct nand_chip *this = mtd->priv;?? ???? ? //取出struct nand_chip结构

??? /* Get buswidth to select the correct functions*/
??? busw = this->options & NAND_BUSWIDTH_16;???? //nand flash的位宽

??? /* check for proper chip_delay setup,set 20us if not */
??? if (!this->chip_delay)?? ?? ?? ?? ?? ?? ??
??? ??? this->chip_delay = 20;

??? /* check,if a user supplied command function given */
??? if (this->cmdfunc == NULL)?? ?? ?? ?? ?? ?? //填充命令函数
??? ??? this->cmdfunc = nand_command;

??? /* check,if a user supplied wait function given */
??? if (this->waitfunc == NULL)?? ?? ?? ?? ?? ?? //填充等待函数
??? ??? this->waitfunc = nand_wait;

??? if (!this->select_chip)?? ?? ?? ?? ?? ?? ??? //s3c2410_nand_init_chip中已定义
??? ??? this->select_chip = nand_select_chip;
??? if (!this->write_byte)?? ?? ?? ?? ?? ?? ?? ? //使用默认的
??? ??? this->write_byte = busw ? nand_write_byte16 : nand_write_byte;
??? if (!this->read_byte)?? ?? ?? ?? ?? ?? ?? ?? //使用默认的
??? ??? this->read_byte = busw ? nand_read_byte16 : nand_read_byte;
??? if (!this->write_word)?? ?? ?? ?? ?? ?? ?? ? //使用默认的
??? ??? this->write_word = nand_write_word;
??? if (!this->read_word)?? ?? ?? ?? ?? ?? ?? ?? //使用默认的
??? ??? this->read_word = nand_read_word;
??? if (!this->block_bad)?? ?? ?? ?? ?? ?? ?? ?? //使用默认的
??? ??? this->block_bad = nand_block_bad;
??? if (!this->block_markbad)?? ?? ?? ?? ?? ?? ? //使用默认的
??? ??? this->block_markbad = nand_default_block_markbad;
??? if (!this->write_buf)?? ?? ?? ?? ?? ?? ?? ?? //s3c2410_nand_init_chip中已定义
??? ??? this->write_buf = busw ? nand_write_buf16 : nand_write_buf;
??? if (!this->read_buf)?? ?? ?? ?? ?? ?? ?? ??? //s3c2410_nand_init_chip中已定义
??? ??? this->read_buf = busw ? nand_read_buf16 : nand_read_buf;
??? if (!this->verify_buf)?? ?? ?? ?? ?? ?? ?? ? //使用默认的
??? ??? this->verify_buf = busw ? nand_verify_buf16 : nand_verify_buf;
??? if (!this->scan_bbt)?? ?? ?? ?? ?? ?? ?? ??? //使用默认的
??? ??? this->scan_bbt = nand_default_bbt;

??? /* Select the device */
??? this->select_chip(mtd,0);?? ??? //片选，可惜在s3c2410 nand flash控制器中此操作为空

??? /* Send the command for reading device ID */
??? this->cmdfunc (mtd,NAND_CMD_READID,0x00,-1);//发送读ID命令

??? /* Read manufacturer and device IDs */
??? nand_maf_id = this->read_byte(mtd);?? ?? ?? ?? //读取生产商ID
??? nand_dev_id = this->read_byte(mtd);?? ?? ?? ?? //读取设备ID

??? /* Print and store flash device information */
??? for (i = 0; nand_flash_ids[i].name != NULL; i++) {??
//保存着nand flash资料的nand_flash_ids表在include/linux/mtd/nand_ids.c文件中，详细见附录
??? ??? ??? ???
??? ??? if (nand_dev_id != nand_flash_ids[i].id)??? //比较设备ID
??? ??? ??? continue;

??? ??? if (!mtd->name) mtd->name = nand_flash_ids[i].name;?? //填充设备名
??? ??? this->chipsize = nand_flash_ids[i].chipsize << 20;??? //填充设备大小
??? ???
??? ??? /* New devices have all the information in additional id bytes */
??? ??? if (!nand_flash_ids[i].pagesize) {
??? ??? ??? int extid;
??? ??? ??? /* The 3rd id byte contains non relevant data ATM */
??? ??? ??? extid = this->read_byte(mtd);
??? ??? ??? /* The 4th id byte is the important one */
??? ??? ??? extid = this->read_byte(mtd);
??? ??? ??? /* Calc pagesize */
??? ??? ??? mtd->oobblock = 1024 << (extid & 0x3);
??? ??? ??? extid >>= 2;
??? ??? ??? /* Calc oobsize */
??? ??? ??? mtd->oobsize = (8 << (extid & 0x03)) * (mtd->oobblock / 512);
??? ??? ??? extid >>= 2;
??? ??? ??? /* Calc blocksize. Blocksize is multiples of 64KiB */
??? ??? ??? mtd->erasesize = (64 * 1024)? << (extid & 0x03);
??? ??? ??? extid >>= 2;
??? ??? ??? /* Get buswidth information */
??? ??? ??? busw = (extid & 0x01) ? NAND_BUSWIDTH_16 : 0;
??? ???
??? ??? } else {
??? ??? ??? /* Old devices have this data hardcoded in the
??? ??? ??? ?* device id table */
??? ??? ??? mtd->erasesize = nand_flash_ids[i].erasesize;?? //填充檫除单元大小(16k)
??? ??? ??? mtd->oobblock = nand_flash_ids[i].pagesize;?? ? //填充页大小(512)
??? ??? ??? mtd->oobsize = mtd->oobblock / 32;?? ?? ?? ?? ? //oob大小(512/32=16)
??? ??? ??? busw = nand_flash_ids[i].options & NAND_BUSWIDTH_16;//获取nand flash表中定义的位宽
??? ??? }

??? ??? /* Try to identify manufacturer */?? ?? ?? ?? //比较生产商ID
??? ??? for (maf_id = 0; nand_manuf_ids[maf_id].id != 0x0; maf_id++) {
??? ??? ??? if (nand_manuf_ids[maf_id].id == nand_maf_id)
??? ??? ??? ??? break;
??? ??? }

??? ??? /* Check,if buswidth is correct. Hardware drivers should set
??? ??? ?* this correct ! */
??? ??? /用户定义的位宽与芯片实际的位宽不一致，取消nand flash的片选
??? ??? if (busw != (this->options & NAND_BUSWIDTH_16)) {???
??? ??? ??? printk (KERN_INFO "NAND device: Manufacturer ID:"
??? ??? ??? ??? " 0x%02x,Chip ID: 0x%02x (%s %s)/n",
??? ??? ??? ??? nand_manuf_ids[maf_id].name,mtd->name);
??? ??? ??? printk (KERN_WARNING
??? ??? ??? ??? "NAND bus width %d instead %d bit/n",
??? ??? ??? ??? ??? (this->options & NAND_BUSWIDTH_16) ? 16 : 8,
??? ??? ??? ??? ??? busw ? 16 : 8);
??? ??? ??? this->select_chip(mtd,-1);//在s3c2410 nand flash控制器驱动中，此操作为空操作
??? ??? ??? return 1;???
??? ??? }
??? ???
??? ??? /* Calculate the address shift from the page size */
??? ??? //计算页、可檫除单元、nand flash大小的偏移值?
??? ??? this->page_shift = ffs(mtd->oobblock) - 1;
??? ??? this->bbt_erase_shift = this->phys_erase_shift = ffs(mtd->erasesize) - 1;
??? ??? this->chip_shift = ffs(this->chipsize) - 1;

??? ??? /* Set the bad block position */
??? ??? //标注此nand flash为大页还是小页？
??? ??? this->badblockpos = mtd->oobblock > 512 ?
??? ??? ??? NAND_LARGE_BADBLOCK_POS : NAND_SMALL_BADBLOCK_POS;

??? ??? /* Get chip options,preserve non chip based options */
??? ??? //用户没指定的选项从nand flash表中获取补上
??? ??? this->options &= ~NAND_CHIPOPTIONS_MSK;
??? ??? this->options |= nand_flash_ids[i].options & NAND_CHIPOPTIONS_MSK;
??? ??? /* Set this as a default. Board drivers can override it,if neccecary */
??? ??? this->options |= NAND_NO_AUTOINCR;
??? ??? /* Check if this is a not a samsung device. Do not clear the options
??? ??? ?* for chips which are not having an extended id.
??? ??? ?*/???
??? ??? if (nand_maf_id != NAND_MFR_SAMSUNG && !nand_flash_ids[i].pagesize)
??? ??? ??? this->options &= ~NAND_SAMSUNG_LP_OPTIONS;
??? ???
??? ??? /* Check for AND chips with 4 page planes */
??? ??? if (this->options & NAND_4PAGE_ARRAY)
??? ??? ??? this->erase_cmd = multi_erase_cmd;
??? ??? else
??? ??? ??? this->erase_cmd = single_erase_cmd;?? ??

??? ??? /* Do not replace user supplied command function ! */
??? ??? if (mtd->oobblock > 512 && this->cmdfunc == nand_command)
??? ??? ??? this->cmdfunc = nand_command_lp;
??? ??? ??? ???
??? ??? printk (KERN_INFO "NAND device: Manufacturer ID:"
??? ??? ??? " 0x%02x,
??? ??? ??? nand_manuf_ids[maf_id].name,nand_flash_ids[i].name);
??? ??? break;
??? }//好的，检测结束^_^

??? if (!nand_flash_ids[i].name) {?? ??
??? ??? printk (KERN_WARNING "No NAND device found!!!/n");
??? ??? this->select_chip(mtd,-1);
??? ??? return 1;
??? }

??? //统计一下同种类型的nand flash有多少块(我板上只有一块)
??? for (i=1; i < maxchips; i++) {
??? ??? this->select_chip(mtd,i);

??? ??? /* Send the command for reading device ID */
??? ??? this->cmdfunc (mtd,-1);

??? ??? /* Read manufacturer and device IDs */
??? ??? if (nand_maf_id != this->read_byte(mtd) ||
??? ??? ??? nand_dev_id != this->read_byte(mtd))
??? ??? ??? break;
??? }
??? if (i > 1)
??? ??? printk(KERN_INFO "%d NAND chips detected/n",i);
???
??? /* Allocate buffers,if neccecary */
??? if (!this->oob_buf) {
??? ??? size_t len;
??? ??? //求出一个檫除单元64K中oob所占用的总空间
??? ??? len = mtd->oobsize << (this->phys_erase_shift - this->page_shift);
??? ??? this->oob_buf = kmalloc (len,GFP_KERNEL);
??? ??? if (!this->oob_buf) {
??? ??? ??? printk (KERN_ERR "nand_scan(): Cannot allocate oob_buf/n");
??? ??? ??? return -ENOMEM;
??? ??? }
??? ??? this->options |= NAND_OOBBUF_ALLOC;//oob空间已分配，置相应的标志位
??? }
???
??? if (!this->data_buf) {
??? ??? size_t len;
??? ??? len = mtd->oobblock + mtd->oobsize;//512+16=128
??? ??? this->data_buf = kmalloc (len,GFP_KERNEL);
??? ??? if (!this->data_buf) {
??? ??? ??? if (this->options & NAND_OOBBUF_ALLOC)
??? ??? ??? ??? kfree (this->oob_buf);
??? ??? ??? printk (KERN_ERR "nand_scan(): Cannot allocate data_buf/n");
??? ??? ??? return -ENOMEM;
??? ??? }
??? ??? this->options |= NAND_DATABUF_ALLOC;//数据空间已分配，置相应的标志位
??? }

??? /* Store the number of chips and calc total size for mtd */
??? this->numchips = i;//记录nand flash片数
??? mtd->size = i * this->chipsize;//计算出nand flash总大小
??? /* Convert chipsize to number of pages per chip -1. */
??? this->pagemask = (this->chipsize >> this->page_shift) - 1;//(64M>>9)-1=128k-1=0x1ffff

??? /* Preset the internal oob buffer */
??? //oob_buf全部置为0xff
??? memset(this->oob_buf,0xff,mtd->oobsize << (this->phys_erase_shift - this->page_shift));

??? /* If no default placement scheme is given,select an
??? ?* appropriate one */
??? if (!this->autooob) {?? //我们选用的是NAND_ECC_SOFT，autooob未设置
??? ??? /* Select the appropriate default oob placement scheme for
??? ??? ?* placement agnostic filesystems */
??? ??? switch (mtd->oobsize) {
??? ??? case 8:
??? ??? ??? this->autooob = &nand_oob_8;
??? ??? ??? break;
??? ??? case 16:
??? ??? ??? this->autooob = &nand_oob_16;//我们的nand flash属于这一类
??? ??? ??? break;
??? ??? case 64:
??? ??? ??? this->autooob = &nand_oob_64;
??? ??? ??? break;
??? ??? default:
??? ??? ??? printk (KERN_WARNING "No oob scheme defined for oobsize %d/n",
??? ??? ??? ??? mtd->oobsize);
??? ??? ??? BUG();
??? ??? }
??? }
注：
??? ECC的东西不是很懂，先跳过^_^ ?

??? /* The number of bytes available for the filesystem to place fs dependend
??? ?* oob data */
??? mtd->oobavail = 0;
??? for (i = 0; this->autooob->oobfree[i][1]; i++)
??? ??? mtd->oobavail += this->autooob->oobfree[i][1];

??? /*
??? ?* check ECC mode,default to software
??? ?* if 3byte/512byte hardware ECC is selected and we have 256 byte pagesize
??? ?* fallback to software ECC
??? */
??? this->eccsize = 256;??? /* set default eccsize */???
??? this->eccbytes = 3;

??? switch (this->eccmode) {
??? case NAND_ECC_HW12_2048:
??? ??? if (mtd->oobblock < 2048) {
??? ??? ??? printk(KERN_WARNING "2048 byte HW ECC not possible on %d byte page size,fallback to SW ECC/n",
??? ??? ??? ?????? mtd->oobblock);
??? ??? ??? this->eccmode = NAND_ECC_SOFT;
??? ??? ??? this->calculate_ecc = nand_calculate_ecc;
??? ??? ??? this->correct_data = nand_correct_data;
??? ??? } else
??? ??? ??? this->eccsize = 2048;
??? ??? break;

??? case NAND_ECC_HW3_512:
??? case NAND_ECC_HW6_512:
??? case NAND_ECC_HW8_512:
??? ??? if (mtd->oobblock == 256) {
??? ??? ??? printk (KERN_WARNING "512 byte HW ECC not possible on 256 Byte pagesize,fallback to SW ECC /n");
??? ??? ??? this->eccmode = NAND_ECC_SOFT;
??? ??? ??? this->calculate_ecc = nand_calculate_ecc;
??? ??? ??? this->correct_data = nand_correct_data;
??? ??? } else
??? ??? ??? this->eccsize = 512; /* set eccsize to 512 */
??? ??? break;
??? ??? ???
??? case NAND_ECC_HW3_256:
??? ??? break;
??? ???
??? case NAND_ECC_NONE:
??? ??? printk (KERN_WARNING "NAND_ECC_NONE selected by board driver. This is not recommended !!/n");
??? ??? this->eccmode = NAND_ECC_NONE;
??? ??? break;

??? case NAND_ECC_SOFT:???
??? ??? this->calculate_ecc = nand_calculate_ecc;
??? ??? this->correct_data = nand_correct_data;
??? ??? break;

??? default:
??? ??? printk (KERN_WARNING "Invalid NAND_ECC_MODE %d/n",this->eccmode);
??? ??? BUG();???
??? }???

??? /* Check hardware ecc function availability and adjust number of ecc bytes per
??? ?* calculation step
??? */
??? switch (this->eccmode) {
??? case NAND_ECC_HW12_2048:
??? ??? this->eccbytes += 4;
??? case NAND_ECC_HW8_512:
??? ??? this->eccbytes += 2;
??? case NAND_ECC_HW6_512:
??? ??? this->eccbytes += 3;
??? case NAND_ECC_HW3_512:
??? case NAND_ECC_HW3_256:
??? ??? if (this->calculate_ecc && this->correct_data && this->enable_hwecc)
??? ??? ??? break;
??? ??? printk (KERN_WARNING "No ECC functions supplied,Hardware ECC not possible/n");
??? ??? BUG();???
??? }
??? ???
??? mtd->eccsize = this->eccsize;
???
??? /* Set the number of read / write steps for one page to ensure ECC generation */
??? switch (this->eccmode) {
??? case NAND_ECC_HW12_2048:
??? ??? this->eccsteps = mtd->oobblock / 2048;
??? ??? break;
??? case NAND_ECC_HW3_512:
??? case NAND_ECC_HW6_512:
??? case NAND_ECC_HW8_512:
??? ??? this->eccsteps = mtd->oobblock / 512;
??? ??? break;
??? case NAND_ECC_HW3_256:
??? case NAND_ECC_SOFT:???
??? ??? this->eccsteps = mtd->oobblock / 256;
??? ??? break;
??? ???
??? case NAND_ECC_NONE:
??? ??? this->eccsteps = 1;
??? ??? break;
??? }
???
??? /* Initialize state,waitqueue and spinlock */
??? this->state = FL_READY;
??? init_waitqueue_head (&this->wq);
??? spin_lock_init (&this->chip_lock);

??? /* De-select the device */
??? this->select_chip(mtd,-1);

??? /* Invalidate the pagebuffer reference */
??? this->pagebuf = -1;

??? /* Fill in remaining MTD driver data */
??? //填充mtd结构的其它部分
??? mtd->type = MTD_NANDFLASH;
??? mtd->flags = MTD_CAP_NANDFLASH | MTD_ECC;
??? mtd->ecctype = MTD_ECC_SW;
??? mtd->erase = nand_erase;
??? mtd->point = NULL;
??? mtd->unpoint = NULL;
??? mtd->read = nand_read;
??? /* nand_read->nand_do_read_ecc->read_buf->s3c2410_nand_read_buf */
??? mtd->write = nand_write;
??? /* nand_write->nand_write_ecc->nand_write_page->write_buf->s3c2410_nand_write_buf */
??? mtd->read_ecc = nand_read_ecc;
??? mtd->write_ecc = nand_write_ecc;
??? mtd->read_oob = nand_read_oob;
??? mtd->write_oob = nand_write_oob;
??? mtd->readv = NULL;
??? mtd->writev = nand_writev;
??? mtd->writev_ecc = nand_writev_ecc;
??? mtd->sync = nand_sync;
??? mtd->lock = NULL;
??? mtd->unlock = NULL;
??? mtd->suspend = NULL;
??? mtd->resume = NULL;
??? mtd->block_isbad = nand_block_isbad;
??? mtd->block_markbad = nand_block_markbad;

??? /* and make the autooob the default one */
??? memcpy(&mtd->oobinfo,this->autooob,sizeof(mtd->oobinfo));

??? mtd->owner = THIS_MODULE;
???
??? /* Check,if we should skip the bad block table scan */
??? if (this->options & NAND_SKIP_BBTSCAN)
??? ??? return 0;

??? /* Build bad block table */
??? return this->scan_bbt (mtd);
}

/**
?* nand_command - [DEFAULT] Send command to NAND device
?* @mtd:??? MTD device structure
?* @command:??? the command to be sent
?* @column:??? the column address for this command,-1 if none
?* @page_addr:??? the page address for this command,-1 if none
?*
?* Send command to NAND device. This function is used for small page
?* devices (256/512 Bytes per page)
?*/
static void nand_command (struct mtd_info *mtd,unsigned command,int column,int page_addr)
{
??? register struct nand_chip *this = mtd->priv;

??? /* Begin command latch cycle */
??? this->hwcontrol(mtd,NAND_CTL_SETCLE);??? //选择写入S3C2410_NFCMD寄存器
??? /*
??? ?* Write out the command to the device.
??? ?*/
??? if (command == NAND_CMD_SEQIN) {
??? ??? int readcmd;

??? ??? if (column >= mtd->oobblock) {??? ??? //读/写位置超出512，读oob_data
??? ??? ??? /* OOB area */
??? ??? ??? column -= mtd->oobblock;
??? ??? ??? readcmd = NAND_CMD_READOOB;
??? ??? } else if (column < 256) {??? ??? ??? //读/写位置在前512，使用read0命令
??? ??? ??? /* First 256 bytes --> READ0 */
??? ??? ??? readcmd = NAND_CMD_READ0;
??? ??? } else {??? ??? ??? ??? ??? ??? ??? ? //读/写位置在后512，使用read1命令
??? ??? ??? column -= 256;
??? ??? ??? readcmd = NAND_CMD_READ1;
??? ??? }
??? ??? this->write_byte(mtd,readcmd);??? ??? //写入具体命令
??? }
??? this->write_byte(mtd,command);

??? /* Set ALE and clear CLE to start address cycle */
??? /* 清楚CLE，锁存命令；置位ALE，开始传输地址 */
??? this->hwcontrol(mtd,NAND_CTL_CLRCLE);??? ? //锁存命令

??? if (column != -1 || page_addr != -1) {
??? ??? this->hwcontrol(mtd,NAND_CTL_SETALE);? //选择写入S3C2410_NFADDR寄存器

??? ??? /* Serially input address */
??? ??? if (column != -1) {
??? ??? ??? /* Adjust columns for 16 bit buswidth */
??? ??? ??? if (this->options & NAND_BUSWIDTH_16)
??? ??? ??? ??? column >>= 1;
??? ??? ??? this->write_byte(mtd,column);??? ? //写入列地址
??? ??? }
??? ??? if (page_addr != -1) {??? ??? ??? ????? //写入页地址(分三个字节写入)
??? ??? ??? this->write_byte(mtd,(unsigned char) (page_addr & 0xff));
??? ??? ??? this->write_byte(mtd,(unsigned char) ((page_addr >> 8) & 0xff));
??? ??? ??? /* One more address cycle for devices > 32MiB */
??? ??? ??? if (this->chipsize > (32 << 20))
??? ??? ??? ??? this->write_byte(mtd,(unsigned char) ((page_addr >> 16) & 0x0f));
??? ??? }
??? ??? /* Latch in address */
??? ??? /* 锁存地址 */
??? ??? this->hwcontrol(mtd,NAND_CTL_CLRALE);
??? }

??? /*
??? ?* program and erase have their own busy handlers
??? ?* status and sequential in needs no delay
??? */
??? switch (command) {
??? ??? ???
??? case NAND_CMD_PAGEPROG:
??? case NAND_CMD_ERASE1:
??? case NAND_CMD_ERASE2:
??? case NAND_CMD_SEQIN:
??? case NAND_CMD_STATUS:
??? ??? return;

??? case NAND_CMD_RESET:?? ?? //复位操作
??? ??? ??? ??? ??? ??? ??? ? // 等待nand flash become ready
???? ?? if (this->dev_ready)? //判断nand flash 是否busy(1:ready 0:busy)
??? ??? ??? break;
??? ??? udelay(this->chip_delay);
??? ??? this->hwcontrol(mtd,NAND_CTL_SETCLE);
??? ??? this->write_byte(mtd,NAND_CMD_STATUS);
??? ??? this->hwcontrol(mtd,NAND_CTL_CLRCLE);
??? ??? while ( !(this->read_byte(mtd) & NAND_STATUS_READY));
??? ??? return;

??? /* This applies to read commands */???
??? default:
??? ??? /*
??? ??? ?* If we don't have access to the busy pin,we apply the given
??? ??? ?* command delay
??? ??? */
??? ??? if (!this->dev_ready) {
??? ??? ??? udelay (this->chip_delay);//稍作延迟
??? ??? ??? return;
??? ??? }???
??? }
??? /* Apply this short delay always to ensure that we do wait tWB in
??? ?* any case on any machine. */
??? ndelay (100);

??? nand_wait_ready(mtd);
}

/*
?* Wait for the ready pin,after a command
?* The timeout is catched later.
?*/
static void nand_wait_ready(struct mtd_info *mtd)
{
??? struct nand_chip *this = mtd->priv;
??? unsigned long??? timeo = jiffies + 2;

??? /* wait until command is processed or timeout occures */
??? do {
??? ??? if (this->dev_ready(mtd))? ??? ??? //简单调用this->dev_ready(s3c2410_nand_devready)函数??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ???? 等待nand flash become ready
??? ??? ??? return;
??? ??? touch_softlockup_watchdog();
??? } while (time_before(jiffies,timeo));???
}

/**
?* nand_wait - [DEFAULT]? wait until the command is done
?* @mtd:??? MTD device structure
?* @this:??? NAND chip structure
?* @state:??? state to select the max. timeout value
?*
?* Wait for command done. This applies to erase and program only
?* Erase can take up to 400ms and program up to 20ms according to
?* general NAND and SmartMedia specs
?*
*/
/* 等待知道命令传输完成，适用于檫除和写入命令 */
static int nand_wait(struct mtd_info *mtd,struct nand_chip *this,int state)
{

??? unsigned long??? timeo = jiffies;
??? int??? status;
???
??? if (state == FL_ERASING)
??? ??? ?timeo += (HZ * 400) / 1000;//檫除操作的话，时间相对要长一些
??? else
??? ??? ?timeo += (HZ * 20) / 1000;

??? /* Apply this short delay always to ensure that we do wait tWB in
??? ?* any case on any machine. */
??? ndelay (100);

??? if ((state == FL_ERASING) && (this->options & NAND_IS_AND))
??? ??? this->cmdfunc (mtd,NAND_CMD_STATUS_MULTI,-1,-1);
??? else???
??? ??? this->cmdfunc (mtd,NAND_CMD_STATUS,-1);

??? while (time_before(jiffies,timeo)) {??? ???
??? ??? /* Check,if we were interrupted */
??? ??? if (this->state != state)
??? ??? ??? return 0;
??? ??? /* 等待nand flash become ready */
??? ??? if (this->dev_ready) {
??? ??? ??? if (this->dev_ready(mtd))
??? ??? ??? ??? break;???
??? ??? } else {
??? ??? ??? if (this->read_byte(mtd) & NAND_STATUS_READY)
??? ??? ??? ??? break;
??? ??? }
??? ??? cond_resched();
??? }
??? status = (int) this->read_byte(mtd);
??? return status;
}

/**
?* nand_block_bad - [DEFAULT] Read bad block marker from the chip
?* 检查nand flash中某一页是否为坏块
?* @mtd:??? MTD device structure
?* @ofs:??? offset from device start
?* @getchip:??? 0,if the chip is already selected
?*
?* Check,if the block is bad.
?*/
static int nand_block_bad(struct mtd_info *mtd,loff_t ofs,int getchip)
{
??? int page,chipnr,res = 0;
??? struct nand_chip *this = mtd->priv;
??? u16 bad;

??? if (getchip) {
??? ??? page = (int)(ofs >> this->page_shift);
??? ??? chipnr = (int)(ofs >> this->chip_shift);

??? ??? /* Grab the lock and see if the device is available */
??? ??? nand_get_device (this,mtd,FL_READING);

??? ??? /* Select the NAND device */
??? ??? this->select_chip(mtd,chipnr);
??? } else
??? ??? page = (int) ofs;???

??? if (this->options & NAND_BUSWIDTH_16) {
??? ??? this->cmdfunc (mtd,NAND_CMD_READOOB,this->badblockpos & 0xFE,page & this->pagemask);
??? ??? bad = cpu_to_le16(this->read_word(mtd));
??? ??? if (this->badblockpos & 0x1)
??? ??? ??? bad >>= 1;
??? ??? if ((bad & 0xFF) != 0xff)
??? ??? ??? res = 1;
??? } else {
??? ??? this->cmdfunc (mtd,this->badblockpos,page & this->pagemask);
??? ??? /* 发送读oob_data命令(oob_data的badblockpos (第6)位记录着坏块标志) */
??? ??? if (this->read_byte(mtd) != 0xff)//坏块
??? ??? ??? res = 1;
??? }
??? ???
??? if (getchip) {
??? ??? /* Deselect and wake up anyone waiting on the device */
??? ??? nand_release_device(mtd);
??? }???
???
??? return res;
}

/**
?* nand_default_block_markbad - [DEFAULT] mark a block bad
?* 标志坏块
?* @mtd:??? MTD device structure
?* @ofs:??? offset from device start
?*
?* This is the default implementation,which can be overridden by
?* a hardware specific driver.
*/
static int nand_default_block_markbad(struct mtd_info *mtd,loff_t ofs)
{
??? struct nand_chip *this = mtd->priv;
??? u_char buf[2] = {0,0};
??? size_t??? retlen;
??? int block;
???
??? /* Get block number */
??? block = ((int) ofs) >> this->bbt_erase_shift;
??? if (this->bbt)
??? ??? this->bbt[block >> 2] |= 0x01 << ((block & 0x03) << 1);
??? /*
??? ?? 这个暂时不是很好说：内核维护一个标志bad block表，使用2bit来表示1block。
??? ?? 这个表在开机的时候通过扫描nand flash每个block的头两页的oob数据来生成，
??? ?? 发现坏块后至相应的block标志位为非零(有时候至3，但有时候至1，还没搞明白有什么不同)
???? */

??? /* Do we have a flash based bad block table ? */
??? if (this->options & NAND_USE_FLASH_BBT)//samsun nand flash不属于这种，暂时不去研究，以后同
??? ??? return nand_update_bbt (mtd,ofs);
??? ???
??? /* We write two bytes,so we dont have to mess with 16 bit access */
??? ofs += mtd->oobsize + (this->badblockpos & ~0x01);//???????????????
??? return nand_write_oob (mtd,ofs,2,&retlen,buf);
}

/**
?* nand_verify_buf - [DEFAULT] Verify chip data against buffer
?* 检验nand flash与buffer的数据是否一致
?* @mtd:??? MTD device structure
?* @buf:??? buffer containing the data to compare
?* @len:??? number of bytes to compare
?*
?* Default verify function for 8bit buswith
?*/
static int nand_verify_buf(struct mtd_info *mtd,const u_char *buf,int len)
{
??? int i;
??? struct nand_chip *this = mtd->priv;

??? for (i=0; i<len; i++)
??? ??? if (buf[i] != readb(this->IO_ADDR_R))
??? ??? ??? return -EFAULT;

??? return 0;
}

/**
?* nand_default_bbt - [NAND Interface] Select a default bad block table for the device
?* @mtd:??? MTD device structure
?*
?* This function selects the default bad block table
?* support for the device and calls the nand_scan_bbt function
?*
*/
int nand_default_bbt (struct mtd_info *mtd)
{
??? struct nand_chip *this = mtd->priv;
???
??? /* Default for AG-AND. We must use a flash based
??? ?* bad block table as the devices have factory marked
??? ?* _good_ blocks. Erasing those blocks leads to loss
??? ?* of the good / bad information,so we _must_ store
??? ?* this information in a good / bad table during
??? ?* startup
??? */
??? if (this->options & NAND_IS_AND) {
??? ??? /* Use the default pattern descriptors */
??? ??? if (!this->bbt_td) {???
??? ??? ??? this->bbt_td = &bbt_main_descr;
??? ??? ??? this->bbt_md = &bbt_mirror_descr;
??? ??? }???
??? ??? this->options |= NAND_USE_FLASH_BBT;
??? ??? return nand_scan_bbt (mtd,&agand_flashbased);
??? }
???
???
??? /* Is a flash based bad block table requested ? */
??? if (this->options & NAND_USE_FLASH_BBT) {
??? ??? /* Use the default pattern descriptors */???
??? ??? if (!this->bbt_td) {???
??? ??? ??? this->bbt_td = &bbt_main_descr;
??? ??? ??? this->bbt_md = &bbt_mirror_descr;
??? ??? }
??? ??? if (!this->badblock_pattern) {
??? ??? ??? this->badblock_pattern = (mtd->oobblock > 512) ?
??? ??? ??? ??? &largepage_flashbased : &smallpage_flashbased;
??? ??? }
??? } else {?? ?? //samsun nand flash的坏块表不存在与nand flash里面，需要扫描来生成。
??? ??? this->bbt_td = NULL;
??? ??? this->bbt_md = NULL;
??? ??? if (!this->badblock_pattern) {
??? ??? ??? this->badblock_pattern = (mtd->oobblock > 512) ?
??? ??? ??? ??? &largepage_memorybased : &smallpage_memorybased;
??? ??? }
??? }
??? return nand_scan_bbt (mtd,this->badblock_pattern);
}

/**
?* nand_scan_bbt - [NAND Interface] scan,find,read and maybe create bad block table(s)
?* @mtd:??? MTD device structure
?* @bd:??? ??? descriptor for the good/bad block search pattern
?*
?* The function checks,if a bad block table(s) is/are already
?* available. If not it scans the device for manufacturer
?* marked good / bad blocks and writes the bad block table(s) to
?* the selected place.
?*
?* The bad block table memory is allocated here. It must be freed
?* by calling the nand_free_bbt function.
?*
*/
int nand_scan_bbt (struct mtd_info *mtd,struct nand_bbt_descr *bd)
{
??? struct nand_chip *this = mtd->priv;
??? int len,res = 0;
??? uint8_t *buf;
??? struct nand_bbt_descr *td = this->bbt_td;
??? struct nand_bbt_descr *md = this->bbt_md;

??? len = mtd->size >> (this->bbt_erase_shift + 2);
??? /* Allocate memory (2bit per block) */
??? /* 2bit per block=(2/8)byte per block，所以上面要多右移2位 */
??? this->bbt = kmalloc (len,GFP_KERNEL);
??? if (!this->bbt) {
??? ??? printk (KERN_ERR "nand_scan_bbt: Out of memory/n");
??? ??? return -ENOMEM;
??? }
??? /* Clear the memory bad block table */
??? memset (this->bbt,len);

??? /* If no primary table decriptor is given,scan the device
??? ?* to build a memory based bad block table
??? ?*/
??? if (!td) {
??? ??? if ((res = nand_memory_bbt(mtd,bd))) {
??? ??? ??? printk (KERN_ERR "nand_bbt: Can't scan flash and build the RAM-based BBT/n");
??? ??? ??? kfree (this->bbt);
??? ??? ??? this->bbt = NULL;
??? ??? }
??? ??? return res;
??? }

??? /* Allocate a temporary buffer for one eraseblock incl. oob */
??? /* 分配1 block所需要的oob data空间 */
??? len = (1 << this->bbt_erase_shift);
??? len += (len >> this->page_shift) * mtd->oobsize;
??? buf = kmalloc (len,GFP_KERNEL);
??? if (!buf) {
??? ??? printk (KERN_ERR "nand_bbt: Out of memory/n");
??? ??? kfree (this->bbt);
??? ??? this->bbt = NULL;
??? ??? return -ENOMEM;
??? }
???
??? //由于td、md均为NULL，一下函数基本不起作用，先不去研究它
??? /* Is the bbt at a given page ? */
??? if (td->options & NAND_BBT_ABSPAGE) {
??? ??? res = read_abs_bbts (mtd,td,md);
??? } else {???
??? ??? /* Search the bad block table using a pattern in oob */
??? ??? res = search_read_bbts (mtd,md);
??? }???

??? if (res)
??? ??? res = check_create (mtd,bd);
???
??? /* Prevent the bbt regions from erasing / writing */
??? mark_bbt_region (mtd,td);
??? if (md)
??? ??? mark_bbt_region (mtd,md);
???
??? kfree (buf);
??? return res;
}

/**
?* nand_memory_bbt - [GENERIC] create a memory based bad block table
?* @mtd:??? MTD device structure
?* @bd:??? ??? descriptor for the good/bad block search pattern
?*
?* The function creates a memory based bbt by scanning the device
?* for manufacturer / software marked good / bad blocks
*/
static inline int nand_memory_bbt (struct mtd_info *mtd,struct nand_bbt_descr *bd)
{
??? struct nand_chip *this = mtd->priv;

??? bd->options &= ~NAND_BBT_SCANEMPTY;
??? //我们只需要扫描oob data，不需要扫描全部(512+16bytes的数据)
??? return create_bbt (mtd,this->data_buf,bd,-1);
}

/**
?* create_bbt - [GENERIC] Create a bad block table by scanning the device
?* @mtd:??? MTD device structure
?* @buf:??? temporary buffer
?* @bd:??? ??? descriptor for the good/bad block search pattern
?* @chip:??? create the table for a specific chip,-1 read all chips.
?*??? ??? Applies only if NAND_BBT_PERCHIP option is set
?*
?* Create a bad block table by scanning the device
?* for the given good/bad block identify pattern
?*/
static int create_bbt (struct mtd_info *mtd,uint8_t *buf,struct nand_bbt_descr *bd,int chip)
{
??? struct nand_chip *this = mtd->priv;
??? int i,j,numblocks,len,scanlen;
??? int startblock;
??? loff_t from;
??? size_t readlen,ooblen;

??? printk (KERN_INFO "Scanning device for bad blocks/n");

??? if (bd->options & NAND_BBT_SCANALLPAGES)//扫描所有都页
??? ??? len = 1 << (this->bbt_erase_shift - this->page_shift);//求出每block所含的page数
??? else {
??? ??? if (bd->options & NAND_BBT_SCAN2NDPAGE)//只检查2 page
??? ??? ??? len = 2;
??? ??? else???
??? ??? ??? len = 1;//只检查1 page
??? }

??? if (!(bd->options & NAND_BBT_SCANEMPTY)) {
??? ??? /* We need only read few bytes from the OOB area */
??? ??? /* 我们只需要检查OOB的某些数据 */
??? ??? scanlen = ooblen = 0;
??? ??? readlen = bd->len;
??? } else {
??? ??? /* Full page content should be read */
??? ??? /* 读取整页内容 */
??? ??? scanlen??? = mtd->oobblock + mtd->oobsize;
??? ??? readlen = len * mtd->oobblock;
??? ??? ooblen = len * mtd->oobsize;
??? }

??? if (chip == -1) {
??? ??? /* Note that numblocks is 2 * (real numblocks) here,see i+=2 below as it
??? ??? ?* makes shifting and masking less painful */
??? ??? /* 计算出nand flash所包含都block数目(注意这里总数目经过林乘2操作)*/
??? ??? numblocks = mtd->size >> (this->bbt_erase_shift - 1);
??? ??? startblock = 0;
??? ??? from = 0;
??? } else {
??? ??? if (chip >= this->numchips) {
??? ??? ??? printk (KERN_WARNING "create_bbt(): chipnr (%d) > available chips (%d)/n",
??? ??? ??? ??? chip + 1,this->numchips);
??? ??? ??? return -EINVAL;
??? ??? }
??? ??? numblocks = this->chipsize >> (this->bbt_erase_shift - 1);
??? ??? startblock = chip * numblocks;
??? ??? numblocks += startblock;
??? ??? from = startblock << (this->bbt_erase_shift - 1);
??? }
???
??? for (i = startblock; i < numblocks;) {
??? ??? int ret;
??? ???
??? ??? if (bd->options & NAND_BBT_SCANEMPTY)??? ??? //整页数据读取
??? ??? ??? if ((ret = nand_read_raw (mtd,from,readlen,ooblen)))
??? ??? ??? ??? return ret;

??? ??? for (j = 0; j < len; j++) {
??? ??? ??? if (!(bd->options & NAND_BBT_SCANEMPTY)) {
??? ??? ??? ??? size_t retlen;
??? ??? ??? ???
??? ??? ??? ??? /* Read the full oob until read_oob is fixed to
??? ??? ??? ??? ?* handle single byte reads for 16 bit buswidth */
??? ??? ??? ??? /* 读取当前页的oob区的所有数据 */
??? ??? ??? ??? ret = mtd->read_oob(mtd,from + j * mtd->oobblock,
??? ??? ??? ??? ??? ??? ??? mtd->oobsize,buf);
??? ??? ??? ??? if (ret)
??? ??? ??? ??? ??? return ret;
??? ??? ??? ??? /* 检查oob data的bad block标志位，判断是否是坏块 */
??? ??? ??? ??? if (check_short_pattern (buf,bd)) {
??? ??? ??? ??? ??? this->bbt[i >> 3] |= 0x03 << (i & 0x6);
??? ??? ??? ??? /* 注意：这里i=实际值*2。由于一个block的状态用2bit来表示，那么一个字节可以存放4个block的状态。
??? ??? ??? ??? ?? 这里i>>3刚好是实际block/4，4个block的状态刚好存放在this->bbt所指向的一个字节里面
??? ??? ??? ??? ?*/
??? ??? ??? ??? ??? printk (KERN_WARNING "Bad eraseblock %d at 0x%08x/n",
??? ??? ??? ??? ??? ??? i >> 1,(unsigned int) from);
??? ??? ??? ??? ??? break;
??? ??? ??? ??? }
??? ??? ??? } else {
??? ??? ??? ??? if (check_pattern (&buf[j * scanlen],scanlen,mtd->oobblock,bd)) {
??? ??? ??? ??? ??? this->bbt[i >> 3] |= 0x03 << (i & 0x6);
??? ??? ??? ??? ??? printk (KERN_WARNING "Bad eraseblock %d at 0x%08x/n",(unsigned int) from);
??? ??? ??? ??? ??? break;
??? ??? ??? ??? }
??? ??? ??? }
??? ??? }
??? ??? i += 2;//更新block的序号
??? ??? from += (1 << this->bbt_erase_shift);//更新nand flash的地址
??? }
??? return 0;
}

/**
?* nand_release - [NAND Interface] Free resources held by the NAND device
?* @mtd:??? MTD device structure
*/
void nand_release (struct mtd_info *mtd)
{
??? struct nand_chip *this = mtd->priv;

#ifdef CONFIG_MTD_PARTITIONS
??? /* Deregister partitions */
??? del_mtd_partitions (mtd);
#endif
??? /* Deregister the device */
??? del_mtd_device (mtd);

??? /* Free bad block table memory,if allocated */
??? if (this->bbt)
??? ??? kfree (this->bbt);
??? /* Buffer allocated by nand_scan ? */
??? if (this->options & NAND_OOBBUF_ALLOC)
??? ??? kfree (this->oob_buf);
??? /* Buffer allocated by nand_scan ? */
??? if (this->options & NAND_DATABUF_ALLOC)
??? ??? kfree (this->data_buf);
}

附录：
/arch/arm/mach-s3c2410/dev.c文件：

static struct mtd_partition partition_info[]={
? [0]={
???? name??? :"vivi",
???? size??? :0x20000,
???? offset? :0,
? },[1]={
???? name??? :"param",
???? size??? :0x10000,
???? offset? :0x20000,[2]={
???? name??? :"kernel",
???? size??? :0x1d0000,
???? offset? :0x30000,[3]={
???? name??? :"root",
???? size??? :0x3c00000,
???? offset? :0x200000,
? }
};

struct s3c2410_nand_set nandset={
??? nr_partitions??? :4,
??? partitions??? ?? :partition_info,
};

struct s3c2410_platform_nand superlpplatform={
??? tacls???? :0,
??? twrph0??? :30,
??? twrph1??? :0,
??? sets????? :&nandset,
??? nr_sets?? :1,
};

struct platform_device s3c_device_nand = {
??? .name??? ??? ? = "s3c2410-nand",
??? .id??? ??? ? = -1,
??? .num_resources??? ? = ARRAY_SIZE(s3c_nand_resource),
??? .resource??? ? = s3c_nand_resource,
??? .dev={
??? ??? .platform_data=&superlpplatform
??? }
};

nand_flash_ids表
/driver/mtd/nand/nand_ids.c文件：
struct nand_flash_dev nand_flash_ids[] = {
................................................................................
??? {"NAND 64MiB 3,3V 8-bit",??? 0x76,512,64,0x4000,0},
................................................................................
};
注：
??? 这里只列出常用的samsun 64M Nand Flash的资料，对应的信息请看该结构体的定义：
struct nand_flash_dev {
??? char *name;
??? int id;
??? unsigned long pagesize;
??? unsigned long chipsize;
??? unsigned long erasesize;
??? unsigned long options;
};
可知该nand flash 设备ID号为0x76，页大小为512，大小为64(M)，檫除单元大小为16(K)。?

（编辑：李大同）

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