U-boot分析与移植（4）-U-boot 添加命令

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我们初步了解U-Boot执行流程后，知道

U-Boot的每一个命令都是通过U_BOOT_CMD宏定义的。这个宏在include/command.h头文件中定义，每一个命令定义一个cmd_tbl_t结构体。



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/*命令宏U_BOOT_CMD*/
#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}

/*命令宏U_BOOT_CMD*/
#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}

每一个命令宏U_BOOT_CMD用cmd_tbl_t结构体描述一个命令

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struct cmd_tbl_s {
char *name; /* Command Name */
int maxargs; /* maximum number of arguments */
int repeatable; /* autorepeat allowed? */
/* Implementation function */
int (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
char *usage; /* Usage message (short) */
#ifdef CFG_LONGHELP

char *help; /* Help message (long) */
#endif

#ifdef CONFIG_AUTO_COMPLETE

/* do auto completion on the arguments */
int (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
#endif

};

struct cmd_tbl_s {
char		*name;		/* Command Name			*/
int		maxargs;	/* maximum number of arguments	*/
int		repeatable;	/* autorepeat allowed?		*/
/* Implementation function	*/
int		(*cmd)(struct cmd_tbl_s *, int, int, char *[]);
char		*usage;		/* Usage message	(short)	*/
#ifdef	CFG_LONGHELP
char		*help;		/* Help  message	(long)	*/
#endif
#ifdef CONFIG_AUTO_COMPLETE
/* do auto completion on the arguments */
int		(*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
#endif
};

参数意义是：

name	这是命令名字，不需要用双引号括起来
maxargs	最大参数的个数
rep	命令是否可重复，就是下一次按回车时再执行
cmd	对应的函数指针
usage	字符串表示的简短说明
help	字符串表示的详细说明

在源代码里可发现命令都是在cmd_xxx.c里实现的

现在我们添加一个简单的测试命令

1、在common目录下添加一个hello.c文件

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#include <common.h>

#include <command.h>

#ifdef CONFIG_CMD_HELLO

int do_hello(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
int i;
printf("argc = %d\n",argc);
for(i = 0; i < argc; i++)
printf("i = %d, %s\n",i,argv[i]);
return 0;
}
U_BOOT_CMD(hello,CONFIG_SYS_MAXARGS,0,do_h

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

#ifdef CONFIG_CMD_HELLO
int do_hello(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
int i;
printf("argc = %d\n",argc);
for(i = 0; i < argc; i++)
printf("i = %d, %s\n",i,argv[i]);
return 0;
}
U_BOOT_CMD(hello,CONFIG_SYS_MAXARGS,0,do_h

do_xxx函数必须定义成这样形式：

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cmd_tbl_s 结构体里的成员 int (*cmd)(struct cmd_tbl_s *, int, int, char *[]);

cmd_tbl_s 结构体里的成员  int (*cmd)(struct cmd_tbl_s *, int, int, char *[]);

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

在填参数个数时要注意，CONFIG_SYS_MAXARGS是在include/configs/smdk2140.h里定义的，默认16

2、在common/Makefile中的#command添加如下内容：
COBJS-$(CONFIG_CMD_TEST) += cmd_hello.o
3、在include/configs/smdk2410.h(该文件名根据实际操作，要针对自己的平台文件改，如smdk2410.h等)添加如下内容：
在#include <config_cmd_default.h>后添加：
#define CONFIG_CMD_HELLO

或者在include/config_cmd_default.h文件中，添加该命令的宏定义。
4、编译后下到板上

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U-Boot 2009.11 (12鏈?14 2011 - 00:44:00)

DRAM: 64 MB

Flash: 512 kB

NAND: NAND_ECC_NONE selected by board driver. This is not recommended !!

64 MiB

In: serial

Out: serial

Err: serial

Net: dm9000

Hit any key to stop autoboot: 0

BAI2011/12/13 # hello

argc = 1

i = 0, hello

BAI2011/12/13 # hello this is my test!

argc = 5

i = 0, hello

i = 1, this

i = 2, is

i = 3, my

i = 4, test!

BAI2011/12/13 #