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。
（四）
u-boot- 1.1.6已经可以通过"nand write..."、"nand write.jffs2..."等命令来烧写cramfs、jffs2文件系统映象文件，下面增加"nand write.yaffs..."命令实现文件系统映象的烧写。
1、在commom/cmd_nand.c中增加"nand write.yaffs..."的使用说明，代码添加如下：
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"