實現u-boot對yaffs/yaffs2文件系統下載的支持 · U-boot學習筆記

yaffs2文件系統的移植主要涉及到u-boot對yaffs2文件系統的燒寫支持、linux內核對yaffs2文件系統的支持，以及yaffs2文件系統的制作，現在我們按照從下到上的順序來實現各部分的功能。 1、實現u-boot對yaffs/yaffs2文件系統下載的支持。注意：這里對Nand的操作是基于MTD架構方式。通常一個Nnad Flash存儲設備由若干塊組成，1個塊由若干頁組成。一般128MB以下容量的Nand Flash芯片，一頁大小為528B，被依次分為2個256B的主數據區和16B的額外空間；128MB以上容量的Nand Flash芯片，一頁大小通常為2KB。由于Nand Flash出現位反轉的概率較大，一般在讀寫時需要使用ECC進行錯誤檢驗和恢復。 Yaffs/yaffs2文件系統的設計充分考慮到Nand Flash以頁為存取單位等的特點，將文件組織成固定大小的段(Chunk)。以528B的頁為例，Yaffs/yaffs2文件系統使用前512B存儲數據和16B的額外空間存放數據的ECC和文件系統的組織信息等(稱為OOB數據)。通過OOB數據，不但能實現錯誤檢測和壞塊處理，同時還可以避免加載時對整個存儲介質的掃描，加快了文件系統的加載速度。以下是Yaffs/yaffs2文件系統頁的結構說明： ### Yaffs頁結構說明 ???字節???????????????????用途 ?0 - 511??????????????????存儲數據(分為兩個半部) 512 - 515???????????????系統信息 ???516??????????????????????數據狀態字 ???517??????????????????????塊狀態字 518 - 519????????????????系統信息 520 - 522????????????????后半部256字節的ECC 523 - 524????????????????系統信息 525 - 527????????????????前半部256字節的ECC 好了，在了解Nand Flash組成和Yaffs/yaffs2文件系統結構后，我們再回到u-boot中。目前，在u-boot中已經有對Cramfs、Jffs2等文件系統的讀寫支持，但與帶有數據校驗等功能的OOB區的Yaffs/Yaffs2文件系統相比，他們是將所有文件數據簡單的以線性表形式組織的。所以，我們只要在此基礎上通過修改u-boot的Nand Flash讀寫命令，增加處理00B區域數據的功能，即可以實現對Yaffs/Yaffs2文件系統的讀寫支持。實現u-boot對Yaffs或者Yaffs2文件系統的讀寫支持步驟如下： **①、在include/configs/smdk2440.h頭文件中定義一個管理對Yaffs2支持的宏和開啟u-boot中對Nand Flash默認分區的宏，如下：** ~~~ #define CONFIG_MTD_NAND_YAFFS2???1?//定義一個管理對Yaffs2支持的宏 ~~~ ~~~ //開啟Nand Flash默認分區，注意此處的分區要和你的內核中的分區保持一致 #define MTDIDS_DEFAULT "nand0=nandflash0" #define MTDPARTS_DEFAULT "mtdparts=nandflash0:256k(bootloader)," \ ???????????????????? "128k(params)," \ ???????????????????? "2m(kernel)," \ ???????????????????? "-(root)" ~~~ ? **②、在common/cmd_nand.c?原來對Nand操作的命令集列表中添加Yaffs2對Nand的寫命令，如下：//在U_BOOT_CMD中添加** ~~~ U_BOOT_CMD(nand, CONFIG_SYS_MAXARGS, 1, do_nand, ??? "NAND sub-system", ??? "info - show available NAND devices\n" ??? "nand device [dev] - show or set current device\n" ??? "nand read - addr off|partition size\n" ??? "nand write - addr off|partition size\n" ??? " read/write 'size' bytes starting at offset 'off'\n" ??? " to/from memory address 'addr', skipping bad blocks.\n" ~~~ //注意：這里只添加了yaffs2的寫命令，因為我們只用u-boot下載(即寫)功能，所以我們沒有添加yaffs2讀的命令 ~~~ #if defined(CONFIG_MTD_NAND_YAFFS2) ??? "nand write[.yaffs2] - addr off|partition size - write `size' byte yaffs image\n" ??? "?starting at offset off' from memory address addr' (.yaffs2 for 512+16 NAND)\n" #endif ~~~ ~~~ ??? "nand erase [clean] [off size] - erase 'size' bytes from\n" ??? " offset 'off' (entire device if not specified)\n" ??? "nand bad - show bad blocks\n" ??? "nand dump[.oob] off - dump page\n" ??? "nand scrub - really clean NAND erasing bad blocks (UNSAFE)\n" ??? "nand markbad off [...] - mark bad block(s) at offset (UNSAFE)\n" ??? "nand biterr off - make a bit error at offset (UNSAFE)" #ifdef CONFIG_CMD_NAND_LOCK_UNLOCK ??? "\n" ??? "nand lock [tight] [status]\n" ??? " bring nand to lock state or display locked pages\n" ??? "nand unlock [offset] [size] - unlock section" #endif ); ~~~ **接著，在該文件中對nand操作的do_nand函數中添加yaffs2對nand的操作，如下：** ~~~ if (strncmp(cmd, "read", 4) == 0 || strncmp(cmd, "write", 5) == 0)? ??? { ??????? int read; ??????? if (argc < 4) ??????????? goto usage; ??????? addr = (ulong)simple_strtoul(argv[2], NULL, 16); ??????? read = strncmp(cmd, "read", 4) == 0; /* 1 = read, 0 = write */ ??????? printf("\nNAND %s: ", read ? "read" : "write"); ??????? if (arg_off_size(argc - 3, argv + 3, nand, &off, &size) != 0) ??????????? return 1; ??????? s = strchr(cmd, '.'); ??????? if (!s || !strcmp(s, ".jffs2") || !strcmp(s, ".e") || !strcmp(s, ".i"))? ??????? { ??????????? if (read) ??????????????? ret = nand_read_skip_bad(nand, off, &size, (u_char *)addr); ??????????? else ??????????????? ret = nand_write_skip_bad(nand, off, &size, (u_char *)addr); ??????? } ~~~ //添加yaffs2相關操作，注意該處又關聯到nand_write_skip_bad函數 ~~~ #if defined(CONFIG_MTD_NAND_YAFFS2) ??????? else if (s != NULL && (!strcmp(s, ".yaffs2"))) ??????? { ??????????? nand->rw_oob = 1; ??????????? nand->skipfirstblk = 1; ??????????? ret = nand_write_skip_bad(nand,off,&size,(u_char *)addr); ??????????? nand->skipfirstblk = 0; ??????????? nand->rw_oob = 0; ??????? } #endif ??????? else if (!strcmp(s, ".oob"))? ??????? { ??????????? /* out-of-band data */ ??????????? mtd_oob_ops_t ops =? ??????????? { ??????????????? .oobbuf = (u8 *)addr, ??????????????? .ooblen = size, ??????????????? .mode = MTD_OOB_RAW ??????????? }; ??????????? if (read) ??????????????? ret = nand->read_oob(nand, off, &ops); ??????????? else ??????????????? ret = nand->write_oob(nand, off, &ops); ??????? }? ??????? else? ??????? { ??????????? printf("Unknown nand command suffix '%s'.\n", s); ??????????? return 1; ??????? } ??????? printf(" %zu bytes %s: %s\n", size, read ? "read" : "written", ret ? "ERROR" : "OK"); ??????? return ret == 0 ? 0 : 1; ??? } ~~~ ③、**在include/linux/mtd/mtd.h頭文件的mtd_info結構體中添加上面用到rw_oob和skipfirstblk數據成員，如下：** ~~~ #if defined(CONFIG_MTD_NAND_YAFFS2) ????u_char rw_oob; ????u_char skipfirstblk; #endif ~~~ **④、在第二步關聯的drivers/mtd/nand/nand_util.c?的nand_write_skip_bad函數中添加對Nand OOB的相關操作，如下：** ~~~ int nand_write_skip_bad(nand_info_t *nand, loff_t offset, size_t *length, u_char *buffer) { ??? int rval; ??? size_t left_to_write = *length; ??? size_t len_incl_bad; ??? u_char *p_buffer = buffer; #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??? if(nand->rw_oob==1)???? ??? { ??????? size_t oobsize = nand->oobsize; ??????? size_t datasize = nand->writesize; ??????? int datapages = 0; ??????? if (((*length)%(nand->oobsize+nand->writesize)) != 0)? ??????? { ???????? printf ("Attempt to write error length data!\n"); ???????? return -EINVAL; ???? } ??????? datapages = *length/(datasize+oobsize); ??????? *length = datapages*datasize; ??????? left_to_write = *length; ??? } #endif ??? /* Reject writes, which are not page aligned */ ??? if ((offset & (nand->writesize - 1)) != 0 || ???? (*length & (nand->writesize - 1)) != 0) { ??????? printf ("Attempt to write non page aligned data\n"); ??????? return -EINVAL; ??? } ??? len_incl_bad = get_len_incl_bad (nand, offset, *length); ??? if ((offset + len_incl_bad) >= nand->size) { ??????? printf ("Attempt to write outside the flash area\n"); ??????? return -EINVAL; ??? } #if !defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??? if (len_incl_bad == *length) { ??????? rval = nand_write (nand, offset, length, buffer); ??????? if (rval != 0) ??????????? printf ("NAND write to offset %llx failed %d\n", ??????????????? offset, rval); ??????? return rval; ??? } #endif ??? while (left_to_write > 0) { ??????? size_t block_offset = offset & (nand->erasesize - 1); ??????? size_t write_size; ??????? WATCHDOG_RESET (); ??????? if (nand_block_isbad (nand, offset & ~(nand->erasesize - 1))) { ??????????? printf ("Skip bad block 0x%08llx\n", ??????????????? offset & ~(nand->erasesize - 1)); ??????????? offset += nand->erasesize - block_offset; ??????????? continue; ??????? } #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??????? if(nand->skipfirstblk==1)???? ??????? { ??????????? nand->skipfirstblk=0; ??????????? printf ("Skip the first good block %llx\n", offset & ~(nand->erasesize - 1)); ??????????? offset += nand->erasesize - block_offset; ??????????? continue; ??????? } #endif ??????? if (left_to_write < (nand->erasesize - block_offset)) ??????????? write_size = left_to_write; ??????? else ??????????? write_size = nand->erasesize - block_offset; ????????printf("\rWriting at 0x%llx -- ",offset);?//add yaffs2 file system support ??????? rval = nand_write (nand, offset, &write_size, p_buffer); ??????? if (rval != 0) { ??????????? printf ("NAND write to offset %llx failed %d\n", ??????????????? offset, rval); ??????????? *length -= left_to_write; ??????????? return rval; ??????? } ??????? left_to_write -= write_size; ??????? printf("%d%% is complete.",100-(left_to_write/(*length/100))); ??????? offset += write_size; #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??????? if(nand->rw_oob==1)???? ??????? { ??????????? p_buffer += write_size+(write_size/nand->writesize*nand->oobsize); ??????? }? ??????? else???? ??????? { ??????????? p_buffer += write_size; ??????? } #else ??????? p_buffer += write_size; #endif ??? } ??? return 0; } ~~~ ⑤、**在第四步nand_write_skip_bad函數中我們看到又對nand_write函數進行了訪問，所以這一步是到drivers/mtd/nand/nand_base.c??的nand_write函數中添加對yaffs2的支持，如下：** ~~~ static int nand_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const uint8_t *buf) { ??? struct nand_chip *chip = mtd->priv; ??? int ret; #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??? int oldopsmode = 0; ??? if(mtd->rw_oob==1)???? ??? { ??????? int i = 0; ??????? int datapages = 0; ??????? size_t oobsize = mtd->oobsize; ??????? size_t datasize = mtd->writesize; ??????? uint8_t oobtemp[oobsize]; ??????? datapages = len / (datasize); ??????? for(i = 0; i < (datapages); i++)???? ??????? { ??????????? memcpy((void *)oobtemp, (void *)(buf + datasize * (i + 1)), oobsize); ??????????? memmove((void *)(buf + datasize * (i + 1)), (void *)(buf + datasize * (i + 1) + oobsize), (datapages - (i + 1)) * (datasize) + (datapages - 1) * oobsize); ??????????? memcpy((void *)(buf+(datapages) * (datasize + oobsize) - oobsize), (void *)(oobtemp), oobsize); ??????? } ??? } #endif ??? /* Do not allow reads past end of device */ ??? if ((to + len) > mtd->size) ??????? return -EINVAL; ??? if (!len) ??????? return 0; ??? nand_get_device(chip, mtd, FL_WRITING); ??? chip->ops.len = len; ??? chip->ops.datbuf = (uint8_t *)buf; #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??? if(mtd->rw_oob!=1)???? ??? { ??????? chip->ops.oobbuf = NULL; ??? }? ??? else???? ??? { ??????? chip->ops.oobbuf = (uint8_t *)(buf + len); ??????? chip->ops.ooblen = mtd->oobsize; ??????? oldopsmode = chip->ops.mode; ??????? chip->ops.mode = MTD_OOB_RAW; ??? } #else ??? chip->ops.oobbuf = NULL; #endif ??? ret = nand_do_write_ops(mtd, to, &chip->ops); ??? *retlen = chip->ops.retlen; ??? nand_release_device(mtd); #if defined(CONFIG_MTD_NAND_YAFFS2)?//add yaffs2 file system support ??? chip->ops.mode = oldopsmode; #endif ??? return ret; } ~~~