grep -wnR "boot" common
得到：common/cmd_bootm.c:1162: boot, 1, 1, do_bootd,

打開common/cmd_bootm.c 文件

int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
    int rcode = 0;
#ifndef CFG_HUSH_PARSER
    if (run_command (getenv ("bootcmd"), flag) < 0) rcode = 1;
#else
    if (parse_string_outer(getenv("bootcmd"),
        FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP) != 0 ) rcode = 1;
#endif
    return rcode;
}

U_BOOT_CMD(
    boot,   1,  1,  do_bootd,
    "boot    - boot default, i.e., run 'bootcmd'n",
    NULL
);

U_BOOT_CMD(name,maxargs,repeatable,command,"usage","help")

　各個參數(shù)的意義如下：

   name：命令名，非字符串，但在U_BOOT_CMD中用“#”符號轉化為字符串
   maxargs：命令的最大參數(shù)個數(shù)
   repeatable：是否自動重復（按Enter鍵是否會重復執(zhí)行）
   command：該命令對應的響應函數(shù)指針
   usage：簡短的使用說明（字符串）
   help：較詳細的使用說明（字符串）

#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help) 
　　　　cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage, help}

“##”與“#”都是預編譯操作符，“##”有字符串連接的功能，“#”表示后面緊接著的是一個字符串。

struct cmd_tbl_s {
       char       *name;          /* 命令名 */
       int          maxargs;       /* 最大參數(shù)個數(shù) */
       int          repeatable;    /* 是否自動重復 */
       int          (*cmd)(struct cmd_tbl_s *, int, int, char *[]);  /*  響應函數(shù) */
       char       *usage;         /* 簡短的幫助信息 */
#ifdef    CONFIG_SYS_LONGHELP
       char              *help;           /*  較詳細的幫助信息 */
#endif
#ifdef CONFIG_AUTO_COMPLETE
       /* 自動補全參數(shù) */
       int          (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
#endif
};

typedef struct cmd_tbl_s  cmd_tbl_t;
extern cmd_tbl_t  __u_boot_cmd_start;
extern cmd_tbl_t  __u_boot_cmd_end;

一個cmd_tbl_t結構體變量包含了調(diào)用一條命令的所需要的信息。

 #define Struct_Section  __attribute__ ((unused,section (".u_boot_cmd")))

凡是帶有attribute ((unused,section (“.u_boot_cmd”))屬性聲明的變量都將被存放在”.u_boot_cmd”段中，并且即使該變量沒有在代碼中顯式的使用編譯器也不產(chǎn)生警告信息。

. = .;
__u_boot_cmd_start = .;          /*將 __u_boot_cmd_start指定為當前地址 */
.u_boot_cmd : { *(.u_boot_cmd) }
__u_boot_cmd_end = .;           /*  將__u_boot_cmd_end指定為當前地址  */

　　　　cmd_tbl_t __u_boot_cmd_boot __attribute__ ((unused,section (".u_boot_cmd"))) = {boot, 1, 1, do_bootd, "boot    - boot default, i.e., run 'bootcmd'n", " NULL"}

int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
    int rcode = 0;
#ifndef CFG_HUSH_PARSER
    if (run_command (getenv ("bootcmd"), flag) < 0) rcode = 1;
#else
    if (parse_string_outer(getenv("bootcmd"),
        FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP) != 0 ) rcode = 1;
#endif
    return rcode;
}

        s = getenv ("bootcmd");
    if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
        ......
        run_command (s, 0);
        ......
        }

        /*
         * Find separator, or string end
         * Allow simple escape of ';' by writing ";"
         */
        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;
        }

        /* 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) {
            printf ("Unknown command '%s' - try 'help'n", argv[0]);
            rc = -1;    /* give up after bad command */
            continue;
        }

/*__u_boot_cmd_start與__u_boot_cmd_end間查找命令，并返回cmdtp->name命令的cmd_tbl_t結構。*/
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);

    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++;
        }
    }

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 
#include 
#include 
#include 
int do_czg (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
        int i;
        for(i=0;i

COBJS += cmd_czg.o

make distclean
make 100ask24x0_config
make