更新系统固件的一种思路

    记得以前曾经做过WINCE下面利用EBOOT从SD卡读取文件系统更新NAND种的文件，已实现在文件系统被破坏的情况下，用户可以自己还原，那么如果是LINUX系统呢？

    思路是一样：UBOOT启动至第2阶段（没有自启动系统）-----------判断是否更新内核和文件系统--------------如果接收到了用户命令则从SD卡拷贝文件写入NAND指定位置；反之，则启动系统

    重点是怎么接收到用户指令和从SD卡种拷贝文件；

   

    在UBOOT运行至第2阶段的时候：lib_arm/board.c中调用common/main.c下的main_loop函数

void main_loop (void) { #ifndef CFG_HUSH_PARSER static char lastcommand[CFG_CBSIZE] = { 0, }; int len; int rc = 1; int flag; #endif #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0) char *s; int bootdelay; #endif #ifdef CONFIG_PREBOOT char *p; #endif #ifdef CONFIG_BOOTCOUNT_LIMIT unsigned long bootcount = 0; unsigned long bootlimit = 0; char *bcs; char bcs_set[16]; #endif /* CONFIG_BOOTCOUNT_LIMIT */ #if defined(CONFIG_VFD) && defined(VFD_TEST_LOGO) ulong bmp = 0; /* default bitmap */ extern int trab_vfd (ulong bitmap); #ifdef CONFIG_MODEM_SUPPORT if (do_mdm_init) bmp = 1; /* alternate bitmap */ #endif trab_vfd (bmp); #endif /* CONFIG_VFD && VFD_TEST_LOGO */ #ifdef CONFIG_BOOTCOUNT_LIMIT bootcount = bootcount_load(); bootcount++; bootcount_store (bootcount); sprintf (bcs_set, "%lu", bootcount); setenv ("bootcount", bcs_set); bcs = getenv ("bootlimit"); bootlimit = bcs ? simple_strtoul (bcs, NULL, 10) : 0; #endif /* CONFIG_BOOTCOUNT_LIMIT */ #ifdef CONFIG_MODEM_SUPPORT debug ("DEBUG: main_loop: do_mdm_init=%d/n", do_mdm_init); if (do_mdm_init) { char *str = strdup(getenv("mdm_cmd")); setenv ("preboot", str); /* set or delete definition */ if (str != NULL) free (str); mdm_init(); /* wait for modem connection */ } #endif /* CONFIG_MODEM_SUPPORT */ #ifdef CONFIG_VERSION_VARIABLE { extern char version_string[]; setenv ("ver", version_string); /* set version variable */ } #endif /* CONFIG_VERSION_VARIABLE */ #ifdef CFG_HUSH_PARSER u_boot_hush_start (); #endif #ifdef CONFIG_AUTO_COMPLETE install_auto_complete(); #endif #ifdef CONFIG_PREBOOT if ((p = getenv ("preboot")) != NULL) { # ifdef CONFIG_AUTOBOOT_KEYED int prev = disable_ctrlc(1); /* disable Control C checking */ # endif # ifndef CFG_HUSH_PARSER run_command (p, 0); # else parse_string_outer(p, FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP); # endif # ifdef CONFIG_AUTOBOOT_KEYED disable_ctrlc(prev); /* restore Control C checking */ # endif } #endif /* CONFIG_PREBOOT */ #if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0) s = getenv ("bootdelay"); bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY; debug ("### main_loop entered: bootdelay=%d/n/n", bootdelay); # ifdef CONFIG_BOOT_RETRY_TIME init_cmd_timeout (); # endif /* CONFIG_BOOT_RETRY_TIME */ #ifdef CONFIG_POST if (gd->flags & GD_FLG_POSTFAIL) { s = getenv("failbootcmd"); } else #endif /* CONFIG_POST */ #ifdef CONFIG_BOOTCOUNT_LIMIT if (bootlimit && (bootcount > bootlimit)) { printf ("Warning: Bootlimit (%u) exceeded. Using altbootcmd./n", (unsigned)bootlimit); s = getenv ("altbootcmd"); } else #endif /* CONFIG_BOOTCOUNT_LIMIT */ s = getenv ("bootcmd"); debug ("### main_loop: bootcmd=/"%s/"/n", s ? s : "<UNDEFINED>"); if (bootdelay >= 0 && s && !abortboot (bootdelay)) { # ifdef CONFIG_AUTOBOOT_KEYED int prev = disable_ctrlc(1); /* disable Control C checking */ # endif # ifndef CFG_HUSH_PARSER run_command (s, 0); # else parse_string_outer(s, FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP); # endif # ifdef CONFIG_AUTOBOOT_KEYED disable_ctrlc(prev); /* restore Control C checking */ # endif } # ifdef CONFIG_MENUKEY if (menukey == CONFIG_MENUKEY) { s = getenv("menucmd"); if (s) { # ifndef CFG_HUSH_PARSER run_command (s, 0); # else parse_string_outer(s, FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP); # endif } } #endif /* CONFIG_MENUKEY */ #endif /* CONFIG_BOOTDELAY */ #ifdef CONFIG_AMIGAONEG3SE { extern void video_banner(void); video_banner(); } #endif /* * Main Loop for Monitor Command Processing */ #ifdef CFG_HUSH_PARSER parse_file_outer(); /* This point is never reached */ for (;;); #else for (;;) { #ifdef CONFIG_BOOT_RETRY_TIME if (rc >= 0) { /* Saw enough of a valid command to * restart the timeout. */ reset_cmd_timeout(); } #endif len = readline (CFG_PROMPT); flag = 0; /* assume no special flags for now */ if (len > 0) strcpy (lastcommand, console_buffer); else if (len == 0) flag |= CMD_FLAG_REPEAT; #ifdef CONFIG_BOOT_RETRY_TIME else if (len == -2) { /* -2 means timed out, retry autoboot */ puts ("/nTimed out waiting for command/n"); # ifdef CONFIG_RESET_TO_RETRY /* Reinit board to run initialization code again */ do_reset (NULL, 0, 0, NULL); # else return; /* retry autoboot */ # endif } #endif if (len == -1) puts ("<INTERRUPT>/n"); else rc = run_command (lastcommand, flag); if (rc <= 0) { /* invalid command or not repeatable, forget it */ lastcommand[0] = 0; } } #endif /*CFG_HUSH_PARSER*/ }

这里会做两个判断，调用static __inline__ int abortboot(int bootdelay)
函数，判断是否有用户中断，如果有则进入死循环，接收用户命令，并根据命令，调用相应的函数处理

 

如果你下载过android系统文件，你肯定知道会有类似nand write c0008000 600000 300000等命令，来写入文件；上面run_command函数 这个函数就是处理类似这样的命令，具体实现可以查看代码各函数功能，

既然是让客户自更新，我们也不能让客户按照我们测试人员一样，打开串口信息，一行行敲命令吧，那就完蛋了。。。。

所以我们可以在这里加入我们的更新系统的提示！-------------（1）用户触发更新系统中断；（2）接收中断，调用run_command函数处理事件（将SD卡种文件写入NAND指定位置）

 

对于步骤1；我们可以采用读取某个I/O口状态来判断是否更新系统；

 

对于步骤2：关键是加入我们的处理函数，告诉系统“要从SD卡读取文件写入NAND”

这里就需要了解下run_command函数了

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 "/;" */ 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); /* 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; } /* found - check max args */ if (argc > cmdtp->maxargs) { printf ("Usage:/n%s/n", cmdtp->usage); rc = -1; continue; } #if defined(CONFIG_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 /* 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 -1; /* if stopped then not repeatable */ } return rc ? rc : repeatable; }

 

流程：处理宏定义，分析命令和参数 ， 查找是否有命令 ，执行命令

 

我们可以通过nand write c0008000 600000 300000这个命令来了解整个过程

 

common/cmd_nand.c下 U_BOOT_CMD(nand, CONFIG_SYS_MAXARGS, 1, do_nand..............................下有命令的说明

相应的NAND驱动中就有具体的实现；

 

重要函数：

/* Look up command in command table */
  if ((cmdtp = find_cmd(argv[0])) == NULL)

cmd_tbl_t *find_cmd (const char *cmd)
这里会遍历所有结构体集合

48 . = .; 49 __u_boot_cmd_start = .; 50 .u_boot_cmd : { *(.u_boot_cmd) } 51 __u_boot_cmd_end = .;

find_cmd 函数原型

 

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); 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 */ }

 

所以我们可以定义我们自己的U_BOOT_CMD

类似

U_BOOT_CMD(
 SD, 2, 1, DO_SD,
 "xxxxxxxx/n",
 "xxxxxxxxxxx /n"
 "     -xxxxxxxxxx/n"
);

然后定义DO_SD函数即可