libpayload: Add an option to skip console initialization on startup.

A payload may want to decide whether it uses certain input/output consoles,
or that it wants support for outputing to a particular device but not to use
that device as a console. This change adds a config option which skips the
call to console_init in start_main.

Change-Id: I32b224d4d0bd3a239b402ecb09ee907d53225735
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: http://review.coreboot.org/1732
Tested-by: build bot (Jenkins)
Reviewed-by: Anton Kochkov <anton.kochkov@gmail.com>

payloads/libpayload/Config.in

@@ -147,6 +147,14 @@ endmenu
 
 menu "Console Options"
 
+config SKIP_CONSOLE_INIT
+	bool "Skip initializing the consoles at startup"
+	default n
+	help
+	  Normally, libpayload will initialize console input/output on startup
+	  before the payload itself gets control. This option disables that
+	  behavior and leaves console initialization up to the payload.
+
 config CBMEM_CONSOLE
 	bool "Send output to the in memory CBMEM console"
 	default y

payloads/libpayload/arch/i386/main.c

@@ -49,8 +49,9 @@ void start_main(void)
 	/* Gather system information. */
 	lib_get_sysinfo();
 
-	/* Set up the consoles. */
-	console_init();
+	/* Optionally set up the consoles. */
+	if (!CONFIG_SKIP_CONSOLE_INIT)
+		console_init();
 
 	/*
 	 * Any other system init that has to happen before the

payloads/libpayload/arch/powerpc/main.c

@@ -46,8 +46,9 @@ void start_main(void)
 {
 	extern int main(int argc, char **argv);
 
-	/* Set up the consoles. */
-	console_init();
+	/* Optionally set up the consoles. */
+	if (!CONFIG_SKIP_CONSOLE_INIT)
+		console_init();
 
 	/* Gather system information. */
 	lib_get_sysinfo();