下面以添加menu命令为例分析U-Boot添加命令的方法。

（1）    在common目录下新建cmd_menu.c文件

习惯上把通用命令源代码放在common目录下，与开发板专有命令源代码则放在board/<board_dir>目录下，命名方式只是习惯而已。为了方便阅读和查询习惯以“cmd_<命令名>.c”为文件名。

（2）    定义“menu”命令

在cmd_menu.c中使用如下的代码定义“menu”命令：

U_BOOT_CMD(

menu, 3, 0, do_menu,

"menu - display amenu, to select the items to do something\n",

" - display a menu, toselect the items to do something"

);

其中U_BOOT_CMD命令格式如下：

U_BOOT_CMD(name,maxargs,rep,cmd,usage,help)

各个参数的意义如下：

name：命令名，非字符串，但在U_BOOT_CMD中用“#”符号转化为字符串

maxargs：命令的最大参数个数

rep：是否自动重复（按Enter键是否会重复执行）

cmd：该命令对应的响应函数

usage：简短的使用说明（字符串）

help：较详细的使用说明（字符串）

在内存中保存命令的help字段会占用一定的内存，通过配置U-Boot可以选择是否保存help字段。若在include/configs/mini2440.h中定义了CONFIG_SYS_LONGHELP宏，则在U-Boot中使用help命令查看某个命令的帮助信息时将显示usage和help字段的内容，否则就只显示usage字段的内容。

U_BOOT_CMD宏在include/command.h中定义：

#defineU_BOOT_CMD(name,maxargs,rep,cmd,usage,help) \

cmd_tbl_t__u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage, help}

“##”与“#”都是预编译操作符，“##”有字符串连接的功能，“#”表示后面紧接着的是一个字符串。

其中的cmd_tbl_t在include/command.h中定义如下：

struct cmd_tbl_s {

char *name; /* 命令名 */

int maxargs; /* 最大参数个数 */

int repeatable; /* 是否自动重复 */

int (*cmd)(struct cmd_tbl_s*, int, int, char *[]);  /*  响应函数 */

char *usage; /* 简短的帮助信息 */

#ifdef CONFIG_SYS_LONGHELP

char *help; /*  较详细的帮助信息 */

#endif

#ifdef CONFIG_AUTO_COMPLETE

/* 自动补全参数 */

int (*complete)(int argc,char *argv[], char last_char, int maxv, char *cmdv[]);

#endif

};

typedef struct cmd_tbl_s     cmd_tbl_t;

一个cmd_tbl_t结构体变量包含了调用一条命令的所需要的信息。

其中Struct_Section在include/command.h中定义如下：

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

凡是带有__attribute__((unused,section (".u_boot_cmd"))属性声明的变量都将被存放在".u_boot_cmd"段中，并且即使该变量没有在代码中显式的使用编译器也不产生警告信息。

在U-Boot连接脚本u-boot.lds中定义了".u_boot_cmd"段：

. = .;

__u_boot_cmd_start = .; /*将__u_boot_cmd_start指定为当前地址 */

.u_boot_cmd : {*(.u_boot_cmd) }

__u_boot_cmd_end = .;/*  将__u_boot_cmd_end指定为当前地址  */

#defineStruct_Section  __attribute__ ((unused,section (".u_boot_cmd")))

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

这表明带有“.u_boot_cmd”声明的函数或变量将存储在“u_boot_cmd”段。这样只要将U-Boot所有命令对应的cmd_tbl_t变量加上“.u_boot_cmd”声明，编译器就会自动将其放在“u_boot_cmd”段，查找cmd_tbl_t变量时只要在__u_boot_cmd_start与__u_boot_cmd_end之间查找就可以了。

因此“menu”命令的定义经过宏展开后如下：

cmd_tbl_t __u_boot_cmd_menu__attribute__ ((unused,section (".u_boot_cmd"))) = {menu, 3, 0,do_menu, "menu - display a menu, to select the items to dosomething\n", " - display a menu, to select the items to dosomething"}

实质上就是用U_BOOT_CMD宏定义的信息构造了一个cmd_tbl_t类型的结构体。编译器将该结构体放在“u_boot_cmd”段，执行命令时就可以在“u_boot_cmd”段查找到对应的cmd_tbl_t类型结构体。

（3）    实现命令的函数

即U_BOOT_CMD(name,maxargs,rep,cmd,usage,help)中的cmd参数

 

在cmd_menu.c中添加“menu”命令的响应函数的实现。具体的实现代码略：

int do_menu (cmd_tbl_t*cmdtp, int flag, int argc, char *argv[])

{

/* 实现代码略 */

}

（4）    将common/cmd_menu.c编译进u-boot.bin

在common/Makefile中把目标代码cmd_menu.o也加入一起编译：

在include/configs/mini2440.h加入如代码：

#define CONFIG_BOOT_MENU 1

重新编译下载U-Boot就可以使用menu命令了

（5）menu命令执行的过程

在U-Boot中输入“menu”命令执行时，U-Boot接收输入的字符串“menu”，传递给run_command函数。run_command函数调用common/command.c中实现的find_cmd函数在__u_boot_cmd_start与__u_boot_cmd_end间查找命令，并返回menu命令的cmd_tbl_t结构。然后run_command函数使用返回的cmd_tbl_t结构中的函数指针调用menu命令的响应函数do_menu，从而完成了命令的执行。

（6）例子：TFTP下载，命令很简单。

#include<common.h>
#include <command.h>

/**功能：等待键盘输入***/

static charawaitkey(unsigned long delay, int* error_p)
{
    int i;
    char c;
    if (delay == -1) {
        while (1) {
            if (tstc()) /* we got a keypress */
                return getc();
        }
    }
    else {      
         for (i = 0; i < delay; i++) {
      if (tstc()) /* we got a key press*/
       return getc();
            udelay (10*1000);
        }
    }
    if (error_p)
        *error_p = -1;
    return 0;
}     

/*****提示符，功能说明****/

void main_menu_usage(void)
{
 printf("\r\n######## Hotips TFTPDownLoad for SMDK2440 ########\r\n");
 printf("\r\n");
 printf("[1] 下载 u-boot.bin      写入 Nand Flash\r\n");
 printf("[2] 下载 Linux(uImage)   内核镜像写入 Nand Flash\r\n");
 printf("[3] 下载 yaffs2(fs.yaffs)文件系统镜像写入 Nand Flash\r\n");
 printf("[4] 下载 Linux(uImage)   内核镜像到内存并运行\r\n");
 printf("[5] 重启设备\r\n");
 printf("[q] 退出菜单\r\n");
 printf("\r\n");
 printf("输入选择: ");
}

/***do_menu()的调用函数，命令的具体实现***/

 

voidmenu_shell(void)
{
    char c;
    char cmd_buf[200];

    while (1)
    {
      main_menu_usage();
      c = awaitkey(-1, NULL);
      printf("%c\n", c);
      switch (c)
      {
  case '1':
  {
          strcpy(cmd_buf, "tftp0x32000000 u-boot.bin; nand erase 0x0 0x60000; nand write 0x32000000 0x00x60000");
          run_command(cmd_buf, 0);
          break;
  }
        case '2':
        {
          strcpy(cmd_buf, "tftp0x32000000 uImage; nand erase 0x80000 0x200000; nand write 0x32000000 0x800000x200000");
          run_command(cmd_buf, 0);
     break;
        }
        case '3':
        {
          strcpy(cmd_buf, "tftp0x32000000 fs.yaffs; nand erase 0x280000; nand write.yaffs2 0x32000000 0x280000$(filesize)");
          run_command(cmd_buf, 0);
          break;
        }
  case '4':
        {
          strcpy(cmd_buf, "tftp 0x32000000uImage; bootm 0x32000000");
          run_command(cmd_buf, 0);
          break;
        }
  case '5':
        {
          strcpy(cmd_buf,"reset");
          run_command(cmd_buf, 0);
          break;
        }
        case 'q':
        {
          return;  
           break;
        }
      }
    }
}

int do_menu(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
    menu_shell();
    return 0;
}

U_BOOT_CMD(
 menu, 1, 0, do_menu,
 "Download Menu",
 "U-boot Download Menu byHotips\n"
);

 

USB下载：

#include <common.h>
#include <command.h>

extern char console_buffer[];
extern int readline (const char *const prompt);
extern char awaitkey(unsigned long delay, int* error_p);
extern void download_nkbin_to_flash(void);

/**
 * Parses a string into a number.  The number stored at ptr is
 * potentially suffixed with K (forkilobytes, or 1024 bytes),
 * M (for megabytes, or 1048576 bytes),or G (for gigabytes, or
 * 1073741824).  If the number is suffixed with K, M, or G,then
 * the return value is the numbermultiplied by one kilobyte, one
 * megabyte, or one gigabyte,respectively.
 *
 * @param ptr where parse begins
 * @param retptr output pointer to nextchar after parse completes (output)
 * @return resulting unsigned int
 */
static unsigned long memsize_parse2 (const char *const ptr, const char**retptr)
{
 unsigned long ret = simple_strtoul(ptr,(char **)retptr, 0);
    int sixteen = 1;

 switch(**retptr) {
  case 'G':
  case 'g':
   ret <<= 10;
  case 'M':
  case 'm':
   ret <<= 10;
  case 'K':
  case 'k':
   ret <<= 10;
   (*retptr)++;
            sixteen = 0;
  default:
   break;
 }

    if(sixteen)
        return simple_strtoul(ptr, NULL,16);
  
  return ret;
}

void param_menu_usage()
{
    printf("\r\n##### Parameter Menu#####\r\n");
    printf("[v] View theparameters\r\n");
    printf("[s] Set parameter\r\n");
    printf("[d] Delete parameter\r\n");
    printf("[w] Write the parametersto flash memeory \r\n");
    printf("[q] Quit \r\n");
    printf("Enter your selection:");
}

void param_menu_shell(void)
{
    char c;
    char cmd_buf[256];
    char name_buf[20];
    char val_buf[256];
  
     while (1)
    {
        param_menu_usage();
        c = awaitkey(-1, NULL);
        printf("%c\n", c);
        switch (c)
       {
            case 'v':
            {
                strcpy(cmd_buf,"printenv ");
                printf("Name(enterto view all paramters): ");
                readline(NULL);
                strcat(cmd_buf,console_buffer);
                run_command(cmd_buf, 0);
                break;
            }
          
             case 's':
            {
                sprintf(cmd_buf,"setenv ");

               printf("Name: ");
                readline(NULL);
                strcat(cmd_buf, console_buffer);

               printf("Value: ");
                readline(NULL);
                strcat(cmd_buf, "");
                strcat(cmd_buf,console_buffer);

               run_command(cmd_buf, 0);
                break;
            }
          
             case 'd':
            {
                sprintf(cmd_buf,"setenv ");

               printf("Name: ");
                readline(NULL);
                strcat(cmd_buf,console_buffer);

               run_command(cmd_buf, 0);
                break;
            }
          
             case 'w':
            {
                sprintf(cmd_buf,"saveenv");
                run_command(cmd_buf, 0);
                break;
            }
          
             case 'q':
            {
                return;
                break;
            }
        }
    }
}

void main_menu_usage(void)
{
    printf("\r\n##### 100askBootloader for OpenJTAG #####\r\n");

   printf("[n] Download u-boot to Nand Flash\r\n");
 if (bBootFrmNORFlash())
     printf("[o] Download u-boot toNor Flash\r\n");
    printf("[k] Download Linuxkernel uImage\r\n");
    printf("[j] Download root_jffs2image\r\n");
//    printf("[c] Downloadroot_cramfs image\r\n");
    printf("[y] Download root_yaffsimage\r\n");
    printf("[d] Download to SDRAM& Run\r\n");
    printf("[z] Download zImage intoRAM\r\n");
    printf("[g] Boot linux fromRAM\r\n");
    printf("[f] Format the NandFlash\r\n");
    printf("[s] Set the bootparameters\r\n");
    printf("[b] Boot thesystem\r\n");
    printf("[r] Rebootu-boot\r\n");
    printf("[q] Quit frommenu\r\n");
    printf("Enter your selection:");
}

void menu_shell(void)
{
    char c;
    char cmd_buf[200];
    char *p = NULL;
    unsigned long size;
    unsigned long offset;
    struct mtd_info *mtd =&nand_info[nand_curr_device];

    while(1)
    {
        main_menu_usage();
        c = awaitkey(-1, NULL);
        printf("%c\n", c);
        switch (c)
        {
   case 'n':
   {
                strcpy(cmd_buf,"usbslave 1 0x30000000; nand erase bootloader; nand write.jffs2 0x30000000bootloader $(filesize)");
                run_command(cmd_buf, 0);
                break;
   }
            case 'o':
            {
                if (bBootFrmNORFlash())
                {
                    strcpy(cmd_buf,"usbslave 1 0x30000000; protect off all; erase 0 +$(filesize); cp.b0x30000000 0 $(filesize)");
                    run_command(cmd_buf,0);
                }
    break;
            }
          
             case 'k':
            {
                strcpy(cmd_buf, "usbslave 1 0x30000000;nand erase kernel; nand write.jffs2 0x30000000 kernel $(filesize)");
                run_command(cmd_buf, 0);
                break;
            }

           case 'j':
            {
                strcpy(cmd_buf,"usbslave 1 0x30000000; nand erase root; nand write.jffs2 0x30000000 root$(filesize)");
                run_command(cmd_buf, 0);
                break;
            }
#if 0
            case 'c':
            {
                strcpy(cmd_buf,"usbslave 1 0x30000000; nand erase root; nand write.jffs2 0x30000000 root$(filesize)");
                run_command(cmd_buf, 0);
                break;
            }
#endif
            case 'y':
            {
                strcpy(cmd_buf,"usbslave 1 0x30000000; nand erase root; nand write.yaffs 0x30000000 root$(filesize)");
                run_command(cmd_buf, 0);
                break;
            }

           case 'd':
            {
                extern volatile U32downloadAddress;
                extern int download_run;
              
                 download_run = 1;
                strcpy(cmd_buf,"usbslave 1");
                run_command(cmd_buf, 0);
                download_run = 0;
                sprintf(cmd_buf, "go%x", downloadAddress);
                run_command(cmd_buf, 0);
                break;
            }

   case'z':
   {
    strcpy(cmd_buf, "usbslave 10x30008000");
    run_command(cmd_buf, 0);
    break;
   }

   case'g':
   {
    extern void do_bootm_rawLinux (ulongaddr);
    do_bootm_rawLinux(0x30008000);
   }

           case 'b':
            {
                printf("BootingLinux ...\n");
                strcpy(cmd_buf,"nand read.jffs2 0x30007FC0 kernel; bootm 0x30007FC0");
                run_command(cmd_buf, 0);
                break;
            }

           case 'f':
            {
                strcpy(cmd_buf,"nand erase ");

               printf("Start address: ");
                readline(NULL);
                strcat(cmd_buf,console_buffer);

               printf("Size(eg. 4000000, 0x4000000, 64m and so on): ");
                readline(NULL);
                p = console_buffer;
                size = memsize_parse2(p,&p);
                sprintf(console_buffer," %x", size);
                strcat(cmd_buf,console_buffer);

               run_command(cmd_buf, 0);
                break;
            }

           case 's':
            {
                param_menu_shell();
                break;
            }

           case 'r':
            {
    strcpy(cmd_buf, "reset");
    run_command(cmd_buf, 0);
                break;
            }
          
             case 'q':
            {
                return;  
                 break;
            }

        }
              
     }
}

int do_menu (cmd_tbl_t *cmdtp, int flag, intargc, char *argv[])
{
    menu_shell();
    return 0;
}

U_BOOT_CMD(
 menu, 3, 0, do_menu,
 "menu - display a menu, to selectthe items to do something\n",
 " - display a menu, to select theitems to do something"
);

 

对比两种下载方式我们清楚命令的添加和执行方式了