autoboot: add an option to override keyed autoboot

As originally implemented, setting the AUTOBOOT_KEYED config option will
prevent users from breaking into the autoboot script with ctrl-c. Restore
that option with a new config symbol.

Signed-off-by: Mark Langsdorf <mark.langsdorf@calxeda.com>

common/main.c

@@ -392,13 +392,13 @@ static void process_boot_delay(void)
 	debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
 
 	if (bootdelay != -1 && s && !abortboot(bootdelay)) {
-#ifdef CONFIG_AUTOBOOT_KEYED
+#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
 		int prev = disable_ctrlc(1);	/* disable Control C checking */
 #endif
 
 		run_command_list(s, -1, 0);
 
-#ifdef CONFIG_AUTOBOOT_KEYED
+#if defined(CONFIG_AUTOBOOT_KEYED) && !defined(CONFIG_AUTOBOOT_KEYED_CTRLC)
 		disable_ctrlc(prev);	/* restore Control C checking */
 #endif
 	}

doc/README.autoboot

@@ -74,6 +74,7 @@ What they do
 	"bootretry" is >= 0.
 
   CONFIG_AUTOBOOT_KEYED
+  CONFIG_AUTOBOOT_KEYED_CTRLC
   CONFIG_AUTOBOOT_PROMPT
   CONFIG_AUTOBOOT_DELAY_STR
   CONFIG_AUTOBOOT_STOP_STR
@@ -135,6 +136,13 @@ What they do
 	environment variable you can specify a second, alternate
 	string (which allows you to have two "password" strings).
 
+	The CONFIG_AUTOBOOT_KEYED_CTRLC #define allows for the boot
+	sequence to be interrupted by ctrl-c, in addition to the
+	"bootdelaykey" and "bootstopkey". Setting this variable
+	provides an escape sequence from the limited "password"
+	strings.
+
+
   CONFIG_ZERO_BOOTDELAY_CHECK
 
 	If this option is defined, you can stop the autoboot process