uboot ping代码学习笔记.docVIP

/luoqindong/article/details/6196444 luoqindong的专栏uboot ：v1.1.6start_armboot ??? uboot从start.s启动后会跳转到lib_arm/board.c里的start_armboot函数，从这以后都 ???????? 是C语言代码。start_armboot做了一些初始化化然后在死循环里调用main_loop函数 ： ???? /* main_loop() can return to retry autoboot, if so just run it again. */ ???? for (;;) { ???? main_loop (); ???? }main_loop main_loop是在;common/main.c中定义的，下面是从串中读取命令然后执行的一部分代码： for (;;) { len = readline (CFG_PROMPT); //从串口读入命令 flag = 0; /* assume no special flags for now */ if (len 0) strcpy (lastcommand, console_buffer); else if (len == 0) flag |= CMD_FLAG_REPEAT; } if (len == -1) puts (INTERRUPT\n); else rc = run_command (lastcommand, flag); // 执行命令 if (rc = 0) { /* invalid command or not repeatable, forget it */ lastcommand[0] = 0; } } find_command run_command首先调用find_command在命令列表里查找到输入的命令： /* 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; } find_cmd返回的是cmd_tbl_t类型，cmd_tbl_t里有命令对应的执行函数，再调用具体的cmd_tbl_t ????????? 执行函数来执行命令具体的操作：?? /* OK - call function to do the command */ ?? if ((cmdtp-cmd) (cmdtp, flag, argc, argv) != 0) { ?? rc = -1; ?? } uboot所有的命令都定义在commom目录下，ping命令在cmd_net.c文件里定义，定义如下：??? ??? U_BOOT_CMD( ???? ping, 2, 1, do_ping, ???? ping\t- send ICMP ECHO_REQUEST to network host\n, ???? pingAddress\n ??? );? 5 U_BOOT_CMD U_BOOT_CMD定义如下： /* * Monitor Command * * All commands use a common argument format: * * void function (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]); */ ? 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