接下來我們主要分析main_loop()
common/main.c:
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) /*smdk2410沒定義*/
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 /*smdk2410沒定義*/
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 /*smdk2410沒定義*/
debug ("DEBUG: main_loop: do_mdm_init=%d/n", do_mdm_init);
if (do_mdm_init) {
uchar *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 /*smdk2410沒定義*/
{
extern char version_string[];
setenv ("ver", version_string); /* set version variable */
}
#endif /* CONFIG_VERSION_VARIABLE */
#ifdef CFG_HUSH_PARSER /*smdk2410沒定義*/
u_boot_hush_start ();
#endif
#ifdef CONFIG_AUTO_COMPLETE /*smdk2410沒定義*/
install_auto_complete();
#endif
#ifdef CONFIG_PREBOOT /*smdk2410沒定義*/
if ((p = getenv ("preboot")) != NULL) {
# ifdef CONFIG_AUTOBOOT_KEYED /*smdk2410沒定義*/
int prev = disable_ctrlc(1); /* disable Control C checking */
# endif
# ifndef CFG_HUSH_PARSER /*smdk2410沒定義*/
run_command (p, 0);
# else
parse_string_outer(p, FLAG_PARSE_SEMICOLON |
FLAG_EXIT_FROM_LOOP);
# endif
# ifdef CONFIG_AUTOBOOT_KEYED /*smdk2410沒定義*/
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_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"); /*smdk2410下這個環境變量是空的*/
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
*/
/*
* 最核心的就是下面這個死循環了
*/
#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*/
}
該函數比較長，但核心就是不停的從串口獲取命令並解析執行此命令， 這個功能就在函數尾部的那個死循環裏， 我們重點就是分析這個循環。
先看readline()
common/main.c:
/****************************************************************************/
/*
* Prompt for input and read a line.
* If CONFIG_BOOT_RETRY_TIME is defined and retry_time >= 0,
* time out when time goes past endtime (timebase time in ticks).
* Return: number of read characters
* -1 if break
* -2 if timed out
* 上面的註釋說的很清楚了，就是提示用戶輸入命令，並讀取這個命令
*/
int readline (const char *const prompt)
{
char *p = console_buffer; /* console_buffer 是個全局變量*/
int n = 0; /* buffer index */
int plen = 0; /* prompt length */
int col; /* output column cnt */
char c;
/* print prompt */
if (prompt) { /*如果要輸出提示符，則輸出*/
plen = strlen (prompt);
puts (prompt); //前面分析過了
}
col = plen;
for (;;) {
#ifdef CONFIG_BOOT_RETRY_TIME /*sdmk2410沒定義*/
while (!tstc()) { /* while no incoming data */
if (retry_time >= 0 && get_ticks() > endtime)
return (-2); /* timed out */
}
#endif
WATCHDOG_RESET(); /* Trigger watchdog, if needed */
#ifdef CONFIG_SHOW_ACTIVITY /*sdmk2410沒定義*/
while (!tstc()) {
extern void show_activity(int arg);
show_activity(0);
}
#endif
c = getc(); /*從串口獲取用戶輸入的命令*/
/*
* Special character handling
*/
/*下面這個switch就是處理不同的字符了*/
switch (c) {
case '/r': /* Enter */
case '/n':
*p = '/0';
puts ("/r/n");
return (p - console_buffer); /*輸入結束*/
case '/0': /* nul */ /*忽略，繼續*/
continue;
case 0x03: /* ^C - break*//*呵呵，linux下的ctrl+c功能*/
console_buffer[0] = '/0'; /* discard input */
return (-1);
case 0x15: /* ^U - erase line */ /*刪除*/
while (col > plen) {
puts (erase_seq);
--col;
}
p = console_buffer;
n = 0;
continue;
case 0x17: /* ^W - erase word *//*刪除*/
p=delete_char(console_buffer, p, &col, &n, plen);
while ((n > 0) && (*p != ' ')) {
p=delete_char(console_buffer, p, &col, &n, plen);
}
continue;
case 0x08: /* ^H - backspace */
case 0x7F: /* DEL - backspace */
p=delete_char(console_buffer, p, &col, &n, plen);/*刪除*/
continue;
default: /*獲取常規字符*/
/*
* Must be a normal character then
*/
if (n < CFG_CBSIZE-2) {
if (c == '/t') { /* expand TABs */
#ifdef CONFIG_AUTO_COMPLETE
/* if auto completion triggered just continue */
/*自動補全功能，熟悉linux的肯定知道*/
*p = '/0';
if (cmd_auto_complete(prompt, console_buffer, &n, &col)) {
p = console_buffer + n; /* reset */
continue;
}
#endif
puts (tab_seq+(col&07));
col += 8 - (col&07);
} else {
++col; /* echo input */
putc (c);
}
*p++ = c;/*把字符保存在buffer中*/
++n;
} else { /* Buffer full */
putc ('/a');
}
}
}
}
上面這個函數就是提示用戶輸入，然後一直等待用戶輸入，指到用戶輸入完成, 然後獲取用戶數據，並存入全局變量console_buffer中。
再來回顧下那個for循環
common/main.c:
void main_loop (void)
{
……
#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); /*獲取用戶下的command*/
flag = 0; /* assume no special flags for now */
if (len > 0)
strcpy (lastcommand, console_buffer); /*把command存入lastcommand中*/
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); /*執行command*/
if (rc <= 0) {
/* invalid command or not repeatable, forget it */
lastcommand[0] = 0;
}
}
#endif /*CFG_HUSH_PARSER*/
}
OK！核心中的核心就是run_command函數了，一猜就知道是用戶執行所有用戶下達命令的函數。Let’s go
轉自http://blog.csdn.net/aaronychen/article/details/2815040