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Linux MTD系统剖析【转】

發(fā)布時(shí)間：2025/3/21 linux 15 豆豆

生活随笔收集整理的這篇文章主要介紹了 Linux MTD系统剖析【转】小編覺(jué)得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.

轉(zhuǎn)自：http://blog.csdn.net/lwj103862095/article/details/21545791

版權(quán)聲明：本文為博主原創(chuàng)文章，未經(jīng)博主允許不得轉(zhuǎn)載。

MTD，Memory Technology Device即內(nèi)存技術(shù)設(shè)備，在Linux內(nèi)核中，引入MTD層為NOR FLASH和NAND FLASH設(shè)備提供統(tǒng)一接口。MTD將文件系統(tǒng)與底層FLASH存儲(chǔ)器進(jìn)行了隔離。

如上圖所示，MTD設(shè)備通常可分為四層，從上到下依次是：設(shè)備節(jié)點(diǎn)、MTD設(shè)備層、MTD原始設(shè)備層、硬件驅(qū)動(dòng)層。

Flash硬件驅(qū)動(dòng)層：Flash硬件驅(qū)動(dòng)層負(fù)責(zé)對(duì)Flash硬件的讀、寫(xiě)和擦除操作。MTD設(shè)備的Nand Flash芯片的驅(qū)動(dòng)則drivers/mtd/nand/子目錄下,Nor Flash芯片驅(qū)動(dòng)位于drivers/mtd/chips/子目錄下。

MTD原始設(shè)備層：用于描述MTD原始設(shè)備的數(shù)據(jù)結(jié)構(gòu)是mtd_info，它定義了大量的關(guān)于MTD的數(shù)據(jù)和操作函數(shù)。其中mtdcore.c: ?MTD原始設(shè)備接口相關(guān)實(shí)現(xiàn)，mtdpart.c?: ?MTD分區(qū)接口相關(guān)實(shí)現(xiàn)。

MTD設(shè)備層：基于MTD原始設(shè)備，linux系統(tǒng)可以定義出MTD的塊設(shè)備（主設(shè)備號(hào)31）和字符設(shè)備（設(shè)備號(hào)90）。其中mtdchar.c?: ?MTD字符設(shè)備接口相關(guān)實(shí)現(xiàn)，mtdblock.c?: MTD塊設(shè)備接口相關(guān)實(shí)現(xiàn)。

設(shè)備節(jié)點(diǎn)：通過(guò)mknod在/dev子目錄下建立MTD塊設(shè)備節(jié)點(diǎn)（主設(shè)備號(hào)為31）和MTD字符設(shè)備節(jié)點(diǎn)（主設(shè)備號(hào)為90）。通過(guò)訪(fǎng)問(wèn)此設(shè)備節(jié)點(diǎn)即可訪(fǎng)問(wèn)MTD字符設(shè)備和塊設(shè)備?

MTD數(shù)據(jù)結(jié)構(gòu)：

1.Linux內(nèi)核使用mtd_info結(jié)構(gòu)體表示MTD原始設(shè)備，這其中定義了大量關(guān)于MTD的數(shù)據(jù)和操作函數(shù)（后面將會(huì)看到），所有的mtd_info結(jié)構(gòu)體存放在mtd_table結(jié)構(gòu)體數(shù)據(jù)里。在/drivers/mtd/mtdcore.c里：

[cpp]?view plaincopy? print?

struct?mtd_info?*mtd_table[MAX_MTD_DEVICES];??

2.Linux內(nèi)核使用mtd_part結(jié)構(gòu)體表示分區(qū)，其中mtd_info結(jié)構(gòu)體成員用于描述該分區(qū)，大部分成員由其主分區(qū)mtd_part->master決定，各種函數(shù)也指向主分區(qū)的相應(yīng)函數(shù)。

[cpp]?view plaincopy? print?

struct?mtd_part?{??

????struct?mtd_info?mtd;????????/*?分區(qū)信息,?大部分由master決定?*/??

????struct?mtd_info?*master;????/*?分區(qū)的主分區(qū)?*/??

????uint64_t?offset;????????????/*?分區(qū)的偏移地址?*/??

????int?index;??????????????????/*?分區(qū)號(hào)?(Linux3.0后不存在該字段)?*/??

????struct?list_head?list;??????/*?將mtd_part鏈成一個(gè)鏈表mtd_partitons?*/??

????int?registered;??

};??

mtd_info結(jié)構(gòu)體主要成員，為了便于觀察，將重要的數(shù)據(jù)放在前面，不大重要的編寫(xiě)在后面。

[cpp]?view plaincopy? print?

struct?mtd_info?{??

????u_char?type;?????????/*?MTD類(lèi)型，包括MTD_NORFLASH,MTD_NANDFLASH等(可參考mtd-abi.h)?*/??

????uint32_t?flags;??????/*?MTD屬性標(biāo)志，MTD_WRITEABLE,MTD_NO_ERASE等(可參考mtd-abi.h)?*/??

????uint64_t?size;???????/*?mtd設(shè)備的大小?*/??

????uint32_t?erasesize;??/*?MTD設(shè)備的擦除單元大小，對(duì)于NandFlash來(lái)說(shuō)就是Block的大小?*/??

????uint32_t?writesize;??/*?寫(xiě)大小,?對(duì)于norFlash是字節(jié),對(duì)nandFlash為一頁(yè)?*/??

????uint32_t?oobsize;????/*?OOB字節(jié)數(shù)?*/??

????uint32_t?oobavail;???/*?可用的OOB字節(jié)數(shù)?*/??

????unsigned?int?erasesize_shift;???/*?默認(rèn)為0，不重要?*/??

????unsigned?int?writesize_shift;???/*?默認(rèn)為0，不重要?*/??

????unsigned?int?erasesize_mask;????/*?默認(rèn)為1，不重要?*/??

????unsigned?int?writesize_mask;????/*?默認(rèn)為1，不重要?*/??

????const?char?*name;???????????????/*?名字，???不重要*/??

????int?index;??????????????????????/*?索引號(hào)，不重要?*/??

????int?numeraseregions;????????????/*?通常為1?*/??

????struct?mtd_erase_region_info?*eraseregions;?/*?可變擦除區(qū)域?*/??

??????

????void?*priv;?????/*?設(shè)備私有數(shù)據(jù)指針，對(duì)于NandFlash來(lái)說(shuō)指nand_chip結(jié)構(gòu)體?*/??

????struct?module?*owner;???/*?一般設(shè)置為T(mén)HIS_MODULE?*/??

??????

????/*?擦除函數(shù)?*/??

????int?(*erase)?(struct?mtd_info?*mtd,?struct?erase_info?*instr);??

????/*?讀寫(xiě)flash函數(shù)?*/??

????int?(*read)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len,?size_t?*retlen,?u_char?*buf);??

????int?(*write)?(struct?mtd_info?*mtd,?loff_t?to,?size_t?len,?size_t?*retlen,?const?u_char?*buf);??

????/*?帶oob讀寫(xiě)Flash函數(shù)?*/??

????int?(*read_oob)?(struct?mtd_info?*mtd,?loff_t?from,??

?????????????struct?mtd_oob_ops?*ops);??

????int?(*write_oob)?(struct?mtd_info?*mtd,?loff_t?to,??

?????????????struct?mtd_oob_ops?*ops);??

????int?(*get_fact_prot_info)?(struct?mtd_info?*mtd,?struct?otp_info?*buf,?size_t?len);??

????int?(*read_fact_prot_reg)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len,?size_t?*retlen,?u_char?*buf);??

????int?(*get_user_prot_info)?(struct?mtd_info?*mtd,?struct?otp_info?*buf,?size_t?len);??

????int?(*read_user_prot_reg)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len,?size_t?*retlen,?u_char?*buf);??

????int?(*write_user_prot_reg)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len,?size_t?*retlen,?u_char?*buf);??

????int?(*lock_user_prot_reg)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len);??

????int?(*writev)?(struct?mtd_info?*mtd,?const?struct?kvec?*vecs,?unsigned?long?count,?loff_t?to,?size_t?*retlen);??

????int?(*panic_write)?(struct?mtd_info?*mtd,?loff_t?to,?size_t?len,?size_t?*retlen,?const?u_char?*buf);??

????/*?Sync?*/??

????void?(*sync)?(struct?mtd_info?*mtd);??

????/*?Chip-supported?device?locking?*/??

????int?(*lock)?(struct?mtd_info?*mtd,?loff_t?ofs,?uint64_t?len);??

????int?(*unlock)?(struct?mtd_info?*mtd,?loff_t?ofs,?uint64_t?len);??

????/*?電源管理函數(shù)?*/??

????int?(*suspend)?(struct?mtd_info?*mtd);??

????void?(*resume)?(struct?mtd_info?*mtd);??

????/*?壞塊管理函數(shù)?*/??

????int?(*block_isbad)?(struct?mtd_info?*mtd,?loff_t?ofs);??

????int?(*block_markbad)?(struct?mtd_info?*mtd,?loff_t?ofs);??

????void?(*unpoint)?(struct?mtd_info?*mtd,?loff_t?from,?size_t?len);??

????unsigned?long?(*get_unmapped_area)?(struct?mtd_info?*mtd,??

????????????????????????unsigned?long?len,??

????????????????????????unsigned?long?offset,??

????????????????????????unsigned?long?flags);??

????struct?backing_dev_info?*backing_dev_info;??

????struct?notifier_block?reboot_notifier;??/*?default?mode?before?reboot?*/??

????/*?ECC?status?information?*/??

????struct?mtd_ecc_stats?ecc_stats;??

????int?subpage_sft;??

????struct?device?dev;??

????int?usecount;??

????int?(*get_device)?(struct?mtd_info?*mtd);??

????void?(*put_device)?(struct?mtd_info?*mtd);??

};??

mtd_info結(jié)構(gòu)體中的read()、write()、read_oob()、write_oob()、erase()是MTD設(shè)備驅(qū)動(dòng)要實(shí)現(xiàn)的主要函數(shù)，幸運(yùn)的是Linux大牛已經(jīng)幫我們實(shí)現(xiàn)了一套適合大部分FLASH設(shè)備的mtd_info成員函數(shù)。

如果MTD設(shè)備只有一個(gè)分區(qū)，那么使用下面兩個(gè)函數(shù)注冊(cè)和注銷(xiāo)MTD設(shè)備。

[cpp]?view plaincopy? print?

int?add_mtd_device(struct?mtd_info?*mtd)??

int?del_mtd_device?(struct?mtd_info?*mtd)??

如果MTD設(shè)備存在其他分區(qū)，那么使用下面兩個(gè)函數(shù)注冊(cè)和注銷(xiāo)MTD設(shè)備。
[cpp]?view plaincopy? print?

int?add_mtd_partitions(struct?mtd_info?*master,const?struct?mtd_partition?*parts,int?nbparts)??

int?del_mtd_partitions(struct?mtd_info?*master)??

其中mtd_partition結(jié)構(gòu)體表示分區(qū)的信息

[cpp]?view plaincopy? print?

struct?mtd_partition?{??

????char?*name;?????????????/*?分區(qū)名，如TQ2440_Board_uboot、TQ2440_Board_kernel、TQ2440_Board_yaffs2?*/??

????uint64_t?size;??????????/*?分區(qū)大小?*/??

????uint64_t?offset;????????/*?分區(qū)偏移值?*/??

????uint32_t?mask_flags;????/*?掩碼標(biāo)識(shí)，不重要?*/??

????struct?nand_ecclayout?*ecclayout;???/*?OOB布局?*/??

????struct?mtd_info?**mtdp;?????/*?pointer?to?store?the?MTD?object?*/??

};??

其中nand_ecclayout結(jié)構(gòu)體：??

struct?nand_ecclayout?{??

????__u32?eccbytes;?????/*?ECC字節(jié)數(shù)?*/??

????__u32?eccpos[64];???/*?ECC校驗(yàn)碼在OOB區(qū)域存放位置?*/??

????__u32?oobavail;???????

????/*?除了ECC校驗(yàn)碼之外可用的OOB字節(jié)數(shù)?*/??

????struct?nand_oobfree?oobfree[MTD_MAX_OOBFREE_ENTRIES];??

};??

關(guān)于nand_ecclayout結(jié)構(gòu)體實(shí)例，更多可參考drivers/mtd/nand/nand_base.c下的nand_oob_8、nand_oob_16、nand_oob_64實(shí)例。
MTD設(shè)備層：

mtd字符設(shè)備接口：

/drivers/mtd/mtdchar.c文件實(shí)現(xiàn)了MTD字符設(shè)備接口，通過(guò)它，可以直接訪(fǎng)問(wèn)Flash設(shè)備，與前面的字符驅(qū)動(dòng)一樣，通過(guò)file_operations結(jié)構(gòu)體里面的open()、read()、write()、ioctl()可以讀寫(xiě)Flash，通過(guò)一系列IOCTL 命令可以獲取Flash 設(shè)備信息、擦除Flash、讀寫(xiě)NAND 的OOB、獲取OOB layout 及檢查NAND 壞塊等(MEMGETINFO、MEMERASE、MEMREADOOB、MEMWRITEOOB、MEMGETBADBLOCK IOCRL)?

mtd塊設(shè)備接口：

/drivers/mtd/mtdblock.c文件實(shí)現(xiàn)了MTD塊設(shè)備接口，主要原理是將Flash的erase block 中的數(shù)據(jù)在內(nèi)存中建立映射，然后對(duì)其進(jìn)行修改，最后擦除Flash 上的block，將內(nèi)存中的映射塊寫(xiě)入Flash 塊。整個(gè)過(guò)程被稱(chēng)為read/modify/erase/rewrite 周期。?但是，這樣做是不安全的，當(dāng)下列操作序列發(fā)生時(shí)，read/modify/erase/poweroff，就會(huì)丟失這個(gè)block 塊的數(shù)據(jù)。
MTD硬件驅(qū)動(dòng)層：

Linux內(nèi)核再M(fèi)TD層下實(shí)現(xiàn)了通用的NAND驅(qū)動(dòng)(/driver/mtd/nand/nand_base.c)，因此芯片級(jí)的NAND驅(qū)動(dòng)不再需要實(shí)現(xiàn)mtd_info結(jié)構(gòu)體中的read()、write()、read_oob()、write_oob()等成員函數(shù)。

MTD使用nand_chip來(lái)表示一個(gè)NAND FLASH芯片, 該結(jié)構(gòu)體包含了關(guān)于Nand Flash的地址信息,讀寫(xiě)方法,ECC模式,硬件控制等一系列底層機(jī)制。

[cpp]?view plaincopy? print?

struct?nand_chip?{??

????void??__iomem???*IO_ADDR_R;?????/*?讀8位I/O線(xiàn)地址?*/??

????void??__iomem???*IO_ADDR_W;?????/*?寫(xiě)8位I/O線(xiàn)地址?*/??

????/*?從芯片中讀一個(gè)字節(jié)?*/??

????uint8_t?(*read_byte)(struct?mtd_info?*mtd);???????

????/*?從芯片中讀一個(gè)字?*/??

????u16?????(*read_word)(struct?mtd_info?*mtd);???????

????/*?將緩沖區(qū)內(nèi)容寫(xiě)入芯片?*/??

????void????(*write_buf)(struct?mtd_info?*mtd,?const?uint8_t?*buf,?int?len);??????

????/*?讀芯片讀取內(nèi)容至緩沖區(qū)/?*/??

????void????(*read_buf)(struct?mtd_info?*mtd,?uint8_t?*buf,?int?len);??

????/*?驗(yàn)證芯片和寫(xiě)入緩沖區(qū)中的數(shù)據(jù)?*/??

????int?????(*verify_buf)(struct?mtd_info?*mtd,?const?uint8_t?*buf,?int?len);??

????/*?選中芯片?*/??

????void????(*select_chip)(struct?mtd_info?*mtd,?int?chip);??

????/*?檢測(cè)是否有壞塊?*/??

????int?????(*block_bad)(struct?mtd_info?*mtd,?loff_t?ofs,?int?getchip);??

????/*?標(biāo)記壞塊?*/??

????int?????(*block_markbad)(struct?mtd_info?*mtd,?loff_t?ofs);??

????/*?命令、地址、數(shù)據(jù)控制函數(shù)?*/??

????void????(*cmd_ctrl)(struct?mtd_info?*mtd,?int?dat,unsigned?int?ctrl);??

????/*?設(shè)備是否就緒?*/??

????int?????(*dev_ready)(struct?mtd_info?*mtd);??

????/*?實(shí)現(xiàn)命令發(fā)送?*/??

????void????(*cmdfunc)(struct?mtd_info?*mtd,?unsigned?command,?int?column,?int?page_addr);??

????int?????(*waitfunc)(struct?mtd_info?*mtd,?struct?nand_chip?*this);??

????/*?擦除命令的處理?*/??

????void????(*erase_cmd)(struct?mtd_info?*mtd,?int?page);??

????/*?掃描壞塊?*/??

????int?????(*scan_bbt)(struct?mtd_info?*mtd);??

????int?????(*errstat)(struct?mtd_info?*mtd,?struct?nand_chip?*this,?int?state,?int?status,?int?page);??

????/*?寫(xiě)一頁(yè)?*/??

????int?????(*write_page)(struct?mtd_info?*mtd,?struct?nand_chip?*chip,??

??????????????????????const?uint8_t?*buf,?int?page,?int?cached,?int?raw);??

????int?????chip_delay;?????????/*?由板決定的延遲時(shí)間?*/??

????/*?與具體的NAND芯片相關(guān)的一些選項(xiàng)，如NAND_NO_AUTOINCR，NAND_BUSWIDTH_16等?*/??

????unsigned?int????options;??????

????/*?用位表示的NAND芯片的page大小，如某片NAND芯片?

?????*?的一個(gè)page有512個(gè)字節(jié)，那么page_shift就是9??

?????*/??

????int??????page_shift;??

????/*?用位表示的NAND芯片的每次可擦除的大小，如某片NAND芯片每次可?

?????*?擦除16K字節(jié)(通常就是一個(gè)block的大小)，那么phys_erase_shift就是14?

?????*/??

????int??????phys_erase_shift;??

????/*?用位表示的bad?block?table的大小，通常一個(gè)bbt占用一個(gè)block，?

?????*?所以bbt_erase_shift通常與phys_erase_shift相等?

?????*/??

????int??????bbt_erase_shift;??

????/*?用位表示的NAND芯片的容量?*/??

????int??????chip_shift;??

????/*?NADN?FLASH芯片的數(shù)量?*/??

????int??????numchips;??

????/*?NAND芯片的大小?*/??

????uint64_t?chipsize;??

????int??????pagemask;??

????int??????pagebuf;??

????int??????subpagesize;??

????uint8_t??cellinfo;??

????int??????badblockpos;??

????nand_state_t????state;??

????uint8_t?????*oob_poi;??

????struct?nand_hw_control??*controller;??

????struct?nand_ecclayout???*ecclayout;?/*?ECC布局?*/??

??????

????struct?nand_ecc_ctrl?ecc;???/*?ECC校驗(yàn)結(jié)構(gòu)體，里面有大量的函數(shù)進(jìn)行ECC校驗(yàn)?*/??

????struct?nand_buffers?*buffers;??

????struct?nand_hw_control?hwcontrol;??

????struct?mtd_oob_ops?ops;??

????uint8_t?????*bbt;??

????struct?nand_bbt_descr???*bbt_td;??

????struct?nand_bbt_descr???*bbt_md;??

????struct?nand_bbt_descr???*badblock_pattern;??

????void????????*priv;??

};??

最后，我們來(lái)用圖表的形式來(lái)總結(jié)一下，MTD設(shè)備層、MTD原始設(shè)備層、FLASH硬件驅(qū)動(dòng)層之間的聯(lián)系。