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。