uboot的命令分析

uboot命令：
那么我们在uboot命令行输入命令时它该怎么做呢？
类似于有那么一个结构体:cmd_tbl_t
命令结构体：
{
  .name
  .function
}


int run_command (const char *cmd, int flag)
{
cmd_tbl_t *cmdtp;
char cmdbuf[CFG_CBSIZE]; /* working copy of cmd */
char *token; /* start of token in cmdbuf */
char *sep; /* end of token (separator) in cmdbuf */
char finaltoken[CFG_CBSIZE];
char *str = cmdbuf;
char *argv[CFG_MAXARGS + 1]; /* NULL terminated */
int argc, inquotes;
int repeatable = 1;
int rc = 0;
#ifdef DEBUG_PARSER
printf ("[RUN_COMMAND] cmd[%p]=\"", cmd);
puts (cmd ? cmd : "NULL"); /* use puts - string may be loooong */
puts ("\"\n");
#endif
clear_ctrlc(); /* forget any previous Control C */
if (!cmd || !*cmd) {
return -1; /* empty command */
}
if (strlen(cmd) >= CFG_CBSIZE) {
puts ("## Command too long!\n");
return -1;
}
strcpy (cmdbuf, cmd);
/* Process separators and check for invalid
* repeatable commands
*/
#ifdef DEBUG_PARSER
printf ("[PROCESS_SEPARATORS] %s\n", cmd);
#endif
while (*str) {
/*
* Find separator, or string end
* Allow simple escape of ';' by writing "\;"
*/
                //解析命令 ；隔开的命令一个一个的提出来，用于执行。
for (inquotes = 0, sep = str; *sep; sep++) {
if ((*sep=='\'') &&
   (*(sep-1) != '\\'))
inquotes=!inquotes;
if (!inquotes &&
   (*sep == ';') && /* separator */
   ( sep != str) && /* past string start */
   (*(sep-1) != '\\')) /* and NOT escaped */
break;
}
/*
* Limit the token to data between separators
*/
token = str;
if (*sep) {
str = sep + 1; /* start of command for next pass */
*sep = '\0';
}
else
str = sep; /* no more commands for next pass */
#ifdef DEBUG_PARSER
printf ("token: \"%s\"\n", token);
#endif
/* find macros in this token and replace them */
process_macros (token, finaltoken); //处理宏
/* Extract arguments */
if ((argc = parse_line (finaltoken, argv)) == 0) {
rc = -1; /* no command at all */
continue;
}
/* Look up command in command table */
if ((cmdtp = find_cmd(argv[0])) == NULL) {   //根据argv[0]名字去找到cmdtp 的结构体
printf ("Unknown command '%s' - try 'help'\n", argv[0]);
rc = -1; /* give up after bad command */
continue;
}
#if 0
cmd_tbl_t *find_cmd (const char *cmd)
{
cmd_tbl_t *cmdtp;
cmd_tbl_t *cmdtp_temp = &__u_boot_cmd_start; /*Init value */
const char *p;
int len;
int n_found = 0;
/*
* Some commands allow length modifiers (like "cp.b");
* compare command name only until first dot.
*/
len = ((p = strchr(cmd, '.')) == NULL) ? strlen (cmd) : (p - cmd);
       
        //__u_boot_cmd_start定义于链接脚本里面
        //从头找到尾找到名字相同的返回该结构体
for (cmdtp = &__u_boot_cmd_start;
    cmdtp != &__u_boot_cmd_end;
    cmdtp++) {
if (strncmp (cmd, cmdtp->name, len) == 0) {
if (len == strlen (cmdtp->name))
return cmdtp; /* full match */
cmdtp_temp = cmdtp; /* abbreviated command ? */
n_found++;
}
}
if (n_found == 1) { /* exactly one match */
return cmdtp_temp;
}
return NULL; /* not found or ambiguous command */
}
#endif
/* found - check max args */
if (argc > cmdtp->maxargs) {
printf ("Usage:\n%s\n", cmdtp->usage);
rc = -1;
continue;
}
#if (CONFIG_COMMANDS & CFG_CMD_BOOTD)
/* avoid "bootd" recursion */
if (cmdtp->cmd == do_bootd) {
#ifdef DEBUG_PARSER
printf ("[%s]\n", finaltoken);
#endif
if (flag & CMD_FLAG_BOOTD) {
puts ("'bootd' recursion detected\n");
rc = -1;
continue;
} else {
flag |= CMD_FLAG_BOOTD;
}
}
#endif /* CFG_CMD_BOOTD */
/* OK - call function to do the command */
if ((cmdtp->cmd) (cmdtp, flag, argc, argv) != 0) {
rc = -1;
}
repeatable &= cmdtp->repeatable;
/* Did the user stop this? */
if (had_ctrlc ())
return 0; /* if stopped then not repeatable */
}
return rc ? rc : repeatable;
}