mkyaffs2image工具解析

技术2022-05-20 43

来自：http://blogold.chinaunix.net/u3/104683/showart_2504330.html

mkyaffs2image工具解析文件:mkyaffs2image.tar.gz大小:147KB下载:下载终于可以成功制作页大小为2K + 64 Bytes 的nand flash的image 文件了。令人兴奋啊：)

这两天一直苦于自己制作的yaffs2 image文件系统无法被linux-2.6.29.1内核识别，而使用FriendlyARM的mkyaffs2imag-128M工具就没有这个问题。一开始便判断是mkyaffs2image工具有问题，没有生成正确格式的yaffs2 image文件，从而导致内核无法识别，并抛出以下错误信息：

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……

block 155 is badyaffs_read_super: isCheckpointed 0VFS: Mounted root (yaffs filesystem) readonly on device 31:2.Freeing init memory: 164KWarning: unable to open an initial console.Failed to execute /linuxrc. Attempting defaults...Kernel panic - not syncing: No init found. Try passing init= option to kernel.

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网上查了很多相关的资料，对2K data + 64bytes spare 的nand flash上yaffs2文件的存储格式并没有较为清晰的说明。不知道数据的存储模式，就无法正确生成image文件。苦恼了好几天，甚至有些想放弃了。。。

然而今天得到了一个意外的收获，http://www.bluewatersys.com/quickstart/9260sambootassistant.php上大概阐述了2K yaffs2 nand flash中数据的组织形式(虽然后来发现该文章中关于结构yaffs2_PackedTags的大小表述有错，应该是28字节，而非25字节)，经过修改后，并且纠正相关bug，成功生成正确的yaffs2 image 文件，download进s3c2440开发板后，顺利启动系统。

有一点很重要，就是mkyaffs2image生成的image 文件的OOB区数据格式要与linux kernel对nand flash进行读取时的数据格式保持一致，所以mkyaffs2image.c中来自linux kernel的数据结构，即包含了mtd-abi.h头文件。

PS：下面本人会附上mkyaffs2image.c的全部内容，供朋友们参考，希望给meet with同样error的兄弟们一些帮助：)

PART2 About 64bytes OOB

下图为64bytes OOB区中的数据组织结构：

图1 64bytes OOB area

PS：

1) OOB最前端的2bytes为0xFF 0xFF，用于标识为非坏块。

2) 每256bytes的数据需要3bytes有ECC校验，因此2K的数据需要24bytes的ECC。

以下为经过修改过后的mkyaffs2image.c的源码：

/* * YAFFS: Yet Another Flash File System. A NAND-flash specific file system. * * Copyright (C) 2002-2007 Aleph One Ltd. * for Toby Churchill Ltd and Brightstar Engineering * * Created by Charles Manning <charles@aleph1.co.uk> * Nick Bane modifications flagged NCB * Endian handling patches by James Ng. * mkyaffs2image hacks by NCB * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */

/* * makeyaffs2image.c * * Makes a YAFFS2 file system image that can be used to load up a file system. * Uses default Linux MTD layout - change if you need something different. */ #include <stdlib.h>#include <stdio.h>#include <fcntl.h>#include <sys/types.h>#include <sys/stat.h>#include <dirent.h>#include <string.h>#include <unistd.h>#define __user#include <mtd/mtd-user.h>#include "yaffs_ecc.h"#include "yaffs_guts.h"

#include "yaffs_packedtags2.h"

#include "mtd-abi.h" //ADDED BY LIUHAO 2009-11-11

unsigned yaffs_traceMask=0;

#define MAX_OBJECTS 10000

#define chunkSize 2048#define spareSize 64

//MODIFIED BY LIUHAO 2009-11-11 START//#define PT2_BYTES 25 //Original#define PT2_BYTES 28//MODIFIED BY LIUHAO 2009-11-11 END

const char * mkyaffsimage_c_version = "$Id: mkyaffs2image.c,v 1.4 2007-02-14 01:09:06 wookey Exp $";

static int layout_no;

static struct nand_oobinfo oob_layout[] = { /* KSI: * Dummy "raw" layout - no ECC, all the bytes are free. Does NOT * really work, only used for compatibility with CVS YAFFS2 that * never ever worked with any stock MTD. */ { .useecc = MTD_NANDECC_AUTOPLACE, .eccbytes = 0, .eccpos = {}, .oobfree = { {0, 64} } }, /* KSI: * Regular MTD AUTOPLACED ECC for large page NAND devices, the * only one existing in stock MTD so far. It corresponds to layout# 1 * in command line arguments. Any other layouts could be added to * the list when they made their way in kernel's MTD. The structure * is simply copied from kernel's drivers/mtd/nand/nand_base.c as-is. */ { .useecc = MTD_NANDECC_AUTOPLACE, .eccbytes = 24, .eccpos = { 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63}, .oobfree = { {2, 38} } }, /* End-of-list marker */ { .useecc = -1, }};

typedef struct { dev_t dev; ino_t ino; int obj;} objItem;

static objItem obj_list[MAX_OBJECTS];static int n_obj = 0;static int obj_id = YAFFS_NOBJECT_BUCKETS + 1;

static int nObjects = 0, nDirectories = 0, nPages = 0;

static int outFile;

static int error;

static int convert_endian = 0;

static int obj_compare(const void *a, const void * b){ objItem *oa, *ob;

oa = (objItem *)a; ob = (objItem *)b;

if(oa->dev < ob->dev) return -1; if(oa->dev > ob->dev) return 1; if(oa->ino < ob->ino) return -1; if(oa->ino > ob->ino) return 1;

return 0;}

static void add_obj_to_list(dev_t dev, ino_t ino, int obj){ if(n_obj < MAX_OBJECTS) { obj_list[n_obj].dev = dev; obj_list[n_obj].ino = ino; obj_list[n_obj].obj = obj; n_obj++; qsort(obj_list,n_obj,sizeof(objItem),obj_compare); } else { // oops! not enough space in the object array fprintf(stderr,"Not enough space in object array/n"); exit(2); }}

static int find_obj_in_list(dev_t dev, ino_t ino){ objItem *i = NULL; objItem test;

test.dev = dev; test.ino = ino; if(n_obj > 0) { i = bsearch(&test,obj_list,n_obj,sizeof(objItem),obj_compare); }

if(i) { return i->obj; } return -1;}

static void yaffs_PutDataECC(const __u8 * data, unsigned char *oob_buf){ unsigned char ecc_code[3]; int eccsteps = chunkSize / 256; int eccidx = 0, datidx = 0, i; struct nand_oobinfo *oobsel; __u32 *oob_config;

oobsel = &oob_layout[layout_no]; oob_config = oobsel->eccpos; //LIUHAO: 24bytes的ECC在spare area中的位置

for (; eccsteps; eccsteps--) { yaffs_ECCCalculate (&data[datidx], ecc_code); for (i = 0; i < 3; i++, eccidx++) oob_buf[oob_config[eccidx]] = ecc_code[i]; datidx += 256; }}

/* KSI: * No big endian for now. This is left for a later time. The existing code * is FUBAR. */#if 0/* This little function converts a little endian tag to a big endian tag. * NOTE: The tag is not usable after this other than calculating the CRC * with. */static void little_to_big_endian(yaffs_Tags *tagsPtr){#if 0 // FIXME NCB yaffs_TagsUnion * tags = (yaffs_TagsUnion* )tagsPtr; // Work in bytes. yaffs_TagsUnion temp;

memset(&temp, 0, sizeof(temp)); // Ick, I hate magic numbers. temp.asBytes[0] = ((tags->asBytes[2] & 0x0F) << 4) | ((tags->asBytes[1] & 0xF0) >> 4); temp.asBytes[1] = ((tags->asBytes[1] & 0x0F) << 4) | ((tags->asBytes[0] & 0xF0) >> 4); temp.asBytes[2] = ((tags->asBytes[0] & 0x0F) << 4) | ((tags->asBytes[2] & 0x30) >> 2) | ((tags->asBytes[3] & 0xC0) >> 6); temp.asBytes[3] = ((tags->asBytes[3] & 0x3F) << 2) | ((tags->asBytes[2] & 0xC0) >> 6); temp.asBytes[4] = ((tags->asBytes[6] & 0x03) << 6) | ((tags->asBytes[5] & 0xFC) >> 2); temp.asBytes[5] = ((tags->asBytes[5] & 0x03) << 6) | ((tags->asBytes[4] & 0xFC) >> 2); temp.asBytes[6] = ((tags->asBytes[4] & 0x03) << 6) | (tags->asBytes[7] & 0x3F); temp.asBytes[7] = (tags->asBytes[6] & 0xFC) | ((tags->asBytes[7] & 0xC0) >> 6);

// Now copy it back. tags->asBytes[0] = temp.asBytes[0]; tags->asBytes[1] = temp.asBytes[1]; tags->asBytes[2] = temp.asBytes[2]; tags->asBytes[3] = temp.asBytes[3]; tags->asBytes[4] = temp.asBytes[4]; tags->asBytes[5] = temp.asBytes[5]; tags->asBytes[6] = temp.asBytes[6]; tags->asBytes[7] = temp.asBytes[7];#endif}#endif

static void nandmtd2_pt2buf(unsigned char *buf, yaffs_PackedTags2 *pt){ int i, j = 0, k, n; //MODIFIED BY LIUHAO 2009-11-11 //unsigned char pt2_byte_buf[PT2_BYTES]; //Original unsigned char pt2_byte_buf[PT2_BYTES] = {0}; *((unsigned int *) &pt2_byte_buf[0]) = pt->t.sequenceNumber; *((unsigned int *) &pt2_byte_buf[4]) = pt->t.objectId; *((unsigned int *) &pt2_byte_buf[8]) = pt->t.chunkId; *((unsigned int *) &pt2_byte_buf[12]) = pt->t.byteCount; pt2_byte_buf[16] = pt->ecc.colParity; //MODIFIED BY LIUHAO 2009-11-11 START#if 0 //Original pt2_byte_buf[17] = pt->ecc.lineParity & 0xff; pt2_byte_buf[18] = (pt->ecc.lineParity >> 8) & 0xff; pt2_byte_buf[19] = (pt->ecc.lineParity >> 16) & 0xff; pt2_byte_buf[20] = (pt->ecc.lineParity >> 24) & 0xff; pt2_byte_buf[21] = pt->ecc.lineParityPrime & 0xff; pt2_byte_buf[22] = (pt->ecc.lineParityPrime >> 8) & 0xff; pt2_byte_buf[23] = (pt->ecc.lineParityPrime >> 16) & 0xff; pt2_byte_buf[24] = (pt->ecc.lineParityPrime >> 24) & 0xff;#else pt2_byte_buf[20] = pt->ecc.lineParity & 0xff; pt2_byte_buf[21] = (pt->ecc.lineParity >> 8) & 0xff; pt2_byte_buf[22] = (pt->ecc.lineParity >> 16) & 0xff; pt2_byte_buf[23] = (pt->ecc.lineParity >> 24) & 0xff; pt2_byte_buf[24] = pt->ecc.lineParityPrime & 0xff; pt2_byte_buf[25] = (pt->ecc.lineParityPrime >> 8) & 0xff; pt2_byte_buf[26] = (pt->ecc.lineParityPrime >> 16) & 0xff; pt2_byte_buf[27] = (pt->ecc.lineParityPrime >> 24) & 0xff;#endif

k = oob_layout[layout_no].oobfree[j][0]; n = oob_layout[layout_no].oobfree[j][1]; if (n == 0) { fprintf(stderr, "No OOB space for tags"); exit(-1); } for (i = 0; i < PT2_BYTES; i++) { if (n == 0) { j++; k = oob_layout[layout_no].oobfree[j][0]; n = oob_layout[layout_no].oobfree[j][1]; if (n == 0) { fprintf(stderr, "No OOB space for tags"); exit(-1); } } buf[k++] = pt2_byte_buf[i]; n--; }}

static int write_chunk(__u8 *data, __u32 objId, __u32 chunkId, __u32 nBytes){ yaffs_ExtendedTags t; yaffs_PackedTags2 pt;

yaffs_PackedTags2TagsPart ptt; //ADDED BY LIUHAO 2009-11-11

//ADDED BY LIUHAO 2009-11-11 //unsigned char spare_buf[spareSize]; //Original unsigned char spare_buf[spareSize] = {0};

error = write(outFile,data,chunkSize); if(error < 0) return error;

yaffs_InitialiseTags(&t); t.chunkId = chunkId;// t.serialNumber = 0; t.serialNumber = 1; // **CHECK** t.byteCount = nBytes; t.objectId = objId; t.sequenceNumber = YAFFS_LOWEST_SEQUENCE_NUMBER;

// added NCB **CHECK** t.chunkUsed = 1;

//ADDED BY LIUHAO 2009-11-11 //t.extraHeaderInfoAvailable = 1;

/* KSI: Broken anyway -- e.g. &t is pointer to a wrong type... */#if 0 if (convert_endian) { little_to_big_endian(&t); }#endif

//MODIFIED BY LIUHAO 2009-11-11 START#if 0 yaffs_PackTags2(&pt,&t); //Original#else memset(&pt, 0, sizeof(yaffs_PackedTags2)); yaffs_PackTags2TagsPart(&pt.t,&t); yaffs_ECCCalculateOther( (unsigned char *)&pt.t, sizeof(yaffs_PackedTags2TagsPart), &pt.ecc);#endif//MODIFIED BY LIUHAO 2009-11-11 END

memset(spare_buf, 0xff, sizeof(spare_buf)); if (layout_no == 0) { memcpy(spare_buf, &pt, sizeof(yaffs_PackedTags2)); } else { nandmtd2_pt2buf(spare_buf, &pt); }

yaffs_PutDataECC(data, &spare_buf[0]);

nPages++;

return write(outFile,spare_buf,spareSize);}

#define SWAP32(x) ((((x) & 0x000000FF) << 24) | / (((x) & 0x0000FF00) << 8 ) | / (((x) & 0x00FF0000) >> 8 ) | / (((x) & 0xFF000000) >> 24))

#define SWAP16(x) ((((x) & 0x00FF) << 8) | / (((x) & 0xFF00) >> 8)) /* KSI: Removed for now. TBD later when the proper util (from scratch) is written */#if 0// This one is easier, since the types are more standard. No funky shifts here.static void object_header_little_to_big_endian(yaffs_ObjectHeader* oh){ oh->type = SWAP32(oh->type); // GCC makes enums 32 bits. oh->parentObjectId = SWAP32(oh->parentObjectId); // int oh->sum__NoLongerUsed = SWAP16(oh->sum__NoLongerUsed); // __u16 - Not used, but done for completeness. // name = skip. Char array. Not swapped. oh->yst_mode = SWAP32(oh->yst_mode);#ifdef CONFIG_YAFFS_WINCE // WinCE doesn't implement this, but we need to just in case. // In fact, WinCE would be *THE* place where this would be an issue! oh->notForWinCE[0] = SWAP32(oh->notForWinCE[0]); oh->notForWinCE[1] = SWAP32(oh->notForWinCE[1]); oh->notForWinCE[2] = SWAP32(oh->notForWinCE[2]); oh->notForWinCE[3] = SWAP32(oh->notForWinCE[3]); oh->notForWinCE[4] = SWAP32(oh->notForWinCE[4]);#else // Regular POSIX. oh->yst_uid = SWAP32(oh->yst_uid); oh->yst_gid = SWAP32(oh->yst_gid); oh->yst_atime = SWAP32(oh->yst_atime); oh->yst_mtime = SWAP32(oh->yst_mtime); oh->yst_ctime = SWAP32(oh->yst_ctime);#endif

oh->fileSize = SWAP32(oh->fileSize); // Aiee. An int... signed, at that! oh->equivalentObjectId = SWAP32(oh->equivalentObjectId); // alias - char array. oh->yst_rdev = SWAP32(oh->yst_rdev);

#ifdef CONFIG_YAFFS_WINCE oh->win_ctime[0] = SWAP32(oh->win_ctime[0]); oh->win_ctime[1] = SWAP32(oh->win_ctime[1]); oh->win_atime[0] = SWAP32(oh->win_atime[0]); oh->win_atime[1] = SWAP32(oh->win_atime[1]); oh->win_mtime[0] = SWAP32(oh->win_mtime[0]); oh->win_mtime[1] = SWAP32(oh->win_mtime[1]); oh->roomToGrow[0] = SWAP32(oh->roomToGrow[0]); oh->roomToGrow[1] = SWAP32(oh->roomToGrow[1]); oh->roomToGrow[2] = SWAP32(oh->roomToGrow[2]); oh->roomToGrow[3] = SWAP32(oh->roomToGrow[3]); oh->roomToGrow[4] = SWAP32(oh->roomToGrow[4]); oh->roomToGrow[5] = SWAP32(oh->roomToGrow[5]);#else oh->roomToGrow[0] = SWAP32(oh->roomToGrow[0]); oh->roomToGrow[1] = SWAP32(oh->roomToGrow[1]); oh->roomToGrow[2] = SWAP32(oh->roomToGrow[2]); oh->roomToGrow[3] = SWAP32(oh->roomToGrow[3]); oh->roomToGrow[4] = SWAP32(oh->roomToGrow[4]); oh->roomToGrow[5] = SWAP32(oh->roomToGrow[5]); oh->roomToGrow[6] = SWAP32(oh->roomToGrow[6]); oh->roomToGrow[7] = SWAP32(oh->roomToGrow[7]); oh->roomToGrow[8] = SWAP32(oh->roomToGrow[8]); oh->roomToGrow[9] = SWAP32(oh->roomToGrow[9]); oh->roomToGrow[10] = SWAP32(oh->roomToGrow[10]); oh->roomToGrow[11] = SWAP32(oh->roomToGrow[11]);#endif}#endif

static int write_object_header(int objId, yaffs_ObjectType t, struct stat *s, int parent, const char *name, int equivalentObj, const char * alias){ __u8 bytes[chunkSize]; yaffs_ObjectHeader *oh = (yaffs_ObjectHeader *)bytes; memset(bytes,0xff,sizeof(bytes)); oh->type = t;

oh->parentObjectId = parent; strncpy(oh->name,name,YAFFS_MAX_NAME_LENGTH); if(t != YAFFS_OBJECT_TYPE_HARDLINK) { oh->yst_mode = s->st_mode; oh->yst_uid = s->st_uid;// NCB 12/9/02 oh->yst_gid = s->yst_uid; oh->yst_gid = s->st_gid; oh->yst_atime = s->st_atime; oh->yst_mtime = s->st_mtime; oh->yst_ctime = s->st_ctime; oh->yst_rdev = s->st_rdev; } if(t == YAFFS_OBJECT_TYPE_FILE) { oh->fileSize = s->st_size; } if(t == YAFFS_OBJECT_TYPE_HARDLINK) { oh->equivalentObjectId = equivalentObj; } if(t == YAFFS_OBJECT_TYPE_SYMLINK) { strncpy(oh->alias,alias,YAFFS_MAX_ALIAS_LENGTH); }

/* KSI: FUBAR. Left for a leter time. */#if 0 if (convert_endian) { object_header_little_to_big_endian(oh); }#endif return write_chunk(bytes,objId,0,0xffff); }

static int process_directory(int parent, const char *path){

DIR *dir; struct dirent *entry;

nDirectories++; dir = opendir(path);

if(dir) { while((entry = readdir(dir)) != NULL) { /* Ignore . and .. */ if(strcmp(entry->d_name,".") && strcmp(entry->d_name,"..")) { char full_name[500]; struct stat stats; int equivalentObj; int newObj; sprintf(full_name,"%s/%s",path,entry->d_name); lstat(full_name,&stats); if(S_ISLNK(stats.st_mode) || S_ISREG(stats.st_mode) || S_ISDIR(stats.st_mode) || S_ISFIFO(stats.st_mode) || S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode) || S_ISSOCK(stats.st_mode)) { newObj = obj_id++; nObjects++; printf("Object %d, %s is a ",newObj,full_name); /* We're going to create an object for it */ if((equivalentObj = find_obj_in_list(stats.st_dev, stats.st_ino)) > 0) { /* we need to make a hard link */ printf("hard link to object %d/n",equivalentObj); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_HARDLINK, &stats, parent, entry->d_name, equivalentObj, NULL); } else { add_obj_to_list(stats.st_dev,stats.st_ino,newObj); if(S_ISLNK(stats.st_mode)) { char symname[500]; memset(symname,0, sizeof(symname)); readlink(full_name,symname,sizeof(symname) -1); printf("symlink to /"%s/"/n",symname); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_SYMLINK, &stats, parent, entry->d_name, -1, symname);

} else if(S_ISREG(stats.st_mode)) { printf("file, "); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_FILE, &stats, parent, entry->d_name, -1, NULL);

if(error >= 0) { int h; __u8 bytes[chunkSize]; int nBytes; int chunk = 0; h = open(full_name,O_RDONLY); if(h >= 0) { memset(bytes,0xff,sizeof(bytes)); while((nBytes = read(h,bytes,sizeof(bytes))) > 0) { chunk++; write_chunk(bytes,newObj,chunk,nBytes); memset(bytes,0xff,sizeof(bytes)); } if(nBytes < 0) error = nBytes; printf("%d data chunks written/n",chunk); close(h); } else { perror("Error opening file"); } } } else if(S_ISSOCK(stats.st_mode)) { printf("socket/n"); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL); } else if(S_ISFIFO(stats.st_mode)) { printf("fifo/n"); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL); } else if(S_ISCHR(stats.st_mode)) { printf("character device/n"); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL); } else if(S_ISBLK(stats.st_mode)) { printf("block device/n"); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL); } else if(S_ISDIR(stats.st_mode)) { printf("directory/n"); error = write_object_header(newObj, YAFFS_OBJECT_TYPE_DIRECTORY, &stats, parent, entry->d_name, -1, NULL); process_directory(newObj,full_name); } } } else { printf(" we don't handle this type/n"); } } } closedir(dir); } return 0;

}

void usage(void){ printf("usage: mkyaffs2image layout# dir image_file [convert]/n"); printf(" layout# NAND OOB layout # (0 - raw, 1 - nand_oob_64)/n"); printf(" dir the directory tree to be converted/n"); printf(" image_file the output file to hold the image/n"); printf(" 'convert' make a big-endian img on a little-endian machine. BROKEN !/n"); exit(1);}

int main(int argc, char *argv[]){ struct stat stats; int i; printf("mkyaffs2image: image building tool for YAFFS2 built "__DATE__"/n"); if ((argc < 4) || (sscanf(argv[1], "%u", &layout_no) != 1)) { usage(); }

i = 0; while (oob_layout[i].useecc != -1) i++; if (layout_no >= i) usage();

if ((argc == 5) && (!strncmp(argv[4], "convert", strlen("convert")))) { fprintf (stderr, "WARNING: ENDIAN CONVERSION IS BROKEN/n"); /* KSI: Broken as of now. TBD. Fail. */ usage(); convert_endian = 1; } if(stat(argv[2],&stats) < 0) { printf("Could not stat %s/n",argv[2]); exit(1); } if(!S_ISDIR(stats.st_mode)) { printf(" %s is not a directory/n",argv[2]); exit(1); } outFile = open(argv[3],O_CREAT | O_TRUNC | O_WRONLY, S_IREAD | S_IWRITE); if(outFile < 0) { printf("Could not open output file %s/n",argv[3]); exit(1); } printf("Processing directory %s into image file %s/n",argv[2],argv[3]); error = write_object_header(1, YAFFS_OBJECT_TYPE_DIRECTORY, &stats, 1,"", -1, NULL);

if(error) error = process_directory(YAFFS_OBJECTID_ROOT,argv[2]); close(outFile); if(error < 0) { perror("operation incomplete"); exit(1); } else { printf("Operation complete./n" "%d objects in %d directories/n" "%d NAND pages/n",nObjects, nDirectories, nPages); } close(outFile); exit(0);}

PART2 About 16bytes OOB

另外，下面用关键性的数据结构简单展示一下16bytes OOB区内的组织格式：

typedef struct { unsigned chunkId:20; unsigned serialNumber:2; unsigned byteCountLSB:10; unsigned objectId:18; unsigned ecc:12; unsigned byteCountMSB:2;} yaffs_Tags;

//LIUHAO: yaffs_TagsUnion共用体，方便实现对yaffs_Tags中数据的处理。typedef union { yaffs_Tags asTags; __u8 asBytes[8];} yaffs_TagsUnion;

//LIUHAO: 512bytes data + 16bytes spare时spare区中的数据格式//其中ecc1[3]为512bytes前半区的ecc校验码// ecc2[3]为512bytes后半区的ecc校验码

/* Spare structure for YAFFS1 */typedef struct { __u8 tagByte0; __u8 tagByte1; __u8 tagByte2; __u8 tagByte3; __u8 pageStatus; /* set to 0 to delete the chunk */ __u8 blockStatus; __u8 tagByte4; __u8 tagByte5; __u8 ecc1[3]; __u8 tagByte6; __u8 tagByte7; __u8 ecc2[3];} yaffs_Spare;

总结：

对于未知的领域和问题，唯独我们坚持，才会最终得到正确的答案。一句话说得好：人类最伟大的品质在于坚持，所有的梦想和目标都会因些而实现。

原文地址 http://blog.csdn.net/itismine/archive/2009/11/11/4799770.aspx

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