struct nand_ecclayout

flash芯片
MT29F8G08ABACA
? Open NAND Flash Interface (ONFI) 1.0-compliant1
? Single-level cell (SLC) technology
? Organization
– Page size x8: 4320 bytes (4096 + 224 bytes) //目标flash
– Page size x16: 2160 words (2048 + 112 words)
– Block size: 64 pages (256K + 14K bytes)
– Plane size: 2 planes x 2048 blocks per plane
– Device size: 8Gb: 4096 blocks //目标flash
– Device size: 16Gb: 8192 blocks

使用8bit BCH ECC效验算法，
下面看ecc保存在oob中的位置,主要解析ecc在obb中存放的位置
static struct nand_ecclayout msm_nand_oob_224_x8 = {
   .eccbytes   = 104,
   .eccpos       = {
       0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
       13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
       26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
       39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
       52, 53, 54, 55, 56, 57, 58, 59,   60, 61, 62, 63, 64,
       65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77,
       78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90,
       123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135,
       },
   .oobavail   = 32,
   .oobfree   = {
       {91, 32},
   }
};

eccbytes　是最终通过bch ecc算法算出的校验字节，从芯片可看出，一个page为4096bytes,oob为224bytes
eccpos　　为ecc效验字节存放在oob中的位置
oobavial 还有几个是空闲的
oobfree 空闲的oob的位置是哪些,oob线性地址31~91是空闲的

为什么是ecc是104bytes, 目前使用的是512byte为计算单位，而一个计算单元会产生13bit＊t(t为可以纠正的错位个数)，故(4096/512)*13*8/8 = 104byte

BCH算法没有看懂，所以没有列出来．

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