在uboot里添加yaffs镜像的支持

　　作者：孙晓明，华清远见嵌入式学院讲师。

　　uboot源码默认是不支持yaffs文件系统的，所以我们需要自己修改源码进行支持。

　　首先我们进入U-Boot源码目录添加对yaffs镜像烧写的支持.

　　在commON/CMD_nand.c里仿照jffs2来写一些yaffs的内容：

　　在：

　　U_BOOT_CMD(NAND, 5, 1, do_nand,

　　"nand - NAND sub-system\n",

　　"info - show available NAND devices\n"

　　"nand device [dev] - show or set current device\n"

　　"nand read[.jffs2] - addr off|partition size\n"

　　"nand write[.jffs2] - addr off|partition size - read/write `size' bytes starting\n"

　　" at offset `off' to/from memory address `addr'\n"

　　之后添加nand read.yaffs 的使用说明：

　　"nand read.yaffs - addr off|partition size\n"

　　"nand write.yaffs - addr off|partition size - read/write `size' bytes starting\n"

　　然后在nand命令的处理函数里do_nand中增加对write.yaffs的支持，do_nand在common/cmd_nand.c中实现：

　　在：

　　if (s != NULL &&

　　(!strcmp(s, ".jffs2") || !strcmp(s, ".e") || !strcmp(s, ".i"))) {

　　…….

　　的判断后面加：

　　else if (s != NULL &&

　　(!strcmp(s, ".yaffs") || !strcmp(s, ".e") || !strcmp(s, ".i"))) {

　　if (read) {

　　/* read */

　　nand_read_options_t opts;

　　memset(&opts, 0, sizeof(opts));

　　opts.buffer = (u_char*) addr;

　　opts.length = size;

　　opts.offset = off;

　　opts.readoob = 1;

　　opts.quiet = quiet;

　　ret = nand_read_opts(nand, &opts);

　　} else {

　　/* write */

　　nand_write_options_t opts;

　　memset(&opts, 0, sizeof(opts));

　　opts.buffer = (u_char*) addr;

　　opts.length = size;

　　opts.offset = off;

　　/* opts.forcejffs2 = 1; */

　　//opts.pad = 1;

　　opts.noecc = 1;

　　opts.writeoob = 1;

　　opts.blockalign = 1;

　　opts.quiet = quiet;

　　ret = nand_write_opts(nand, &opts);

　　}

　　}

　　由于前面设置了opts.noecc = 1,不使用ecc校验码，烧写过程中会提示这个信息：

　　Writing data without ECC to NAND-FLASH is not recommended

　　Writing data without ECC to NAND-FLASH is not recommended

　　Writing data without ECC to NAND-FLASH is not recommended

　　Writing data without ECC to NAND-FLASH is not recommended

　　Writing data without ECC to NAND-FLASH is not recommended

　　可以修改driver/mtd/nand/nand_base.c文件的nand_write_page函数，将它去掉，修改如下：

　　case NAND_ECC_NONE:

　　//printk (KERN_WARNING "Writing data without ECC to NAND-FLASH is not ecommended\n");

　　this->write_buf(mtd, this->data_poi, mtd->oobblock);

　　break;

　　修改完这些，U－BOOT就可以支持yaffs文件镜像的烧写了。

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