@@ -78,7 +78,9 @@ If no console device is specified, the first device found capable of
acting as a system console will be used. At this time, the system
first looks for a VGA card and then for a serial port. So if you don't
have a VGA card in your system the first serial port will automatically
-become the console.
+become the console, unless the kernel is configured with the
+CONFIG_NULL_TTY_DEFAULT_CONSOLE option, then it will default to using the
+ttynull device.
You will need to create a new device to use ``/dev/console``. The official
``/dev/console`` is now character device 5,1.
@@ -383,7 +383,24 @@ config NULL_TTY
available or desired.
In order to use this driver, you should redirect the console to this
- TTY, or boot the kernel with console=ttynull.
+ TTY, boot the kernel with console=ttynull, or enable
+ NULL_TTY_DEFAULT_CONSOLE.
+
+ If unsure, say N.
+
+config NULL_TTY_DEFAULT_CONSOLE
+ bool "Support for console on ttynull"
+ depends on NULL_TTY=y && !VT_CONSOLE
+ help
+ Say Y here if you want the NULL TTY to be used as a /dev/console
+ device by default.
+
+ For example, it might be useful to prevent a VT-less kernel from
+ writing the system log to a random device connected to the serial
+ port.
+
+ Another console driver still might get preferred via the command
+ line, SPCR, or the device tree.
If unsure, say N.
@@ -4277,6 +4277,11 @@ void __init console_init(void)
initcall_t call;
initcall_entry_t *ce;
+#ifdef CONFIG_NULL_TTY_DEFAULT_CONSOLE
+ if (!console_set_on_cmdline)
+ add_preferred_console("ttynull", 0, NULL);
+#endif
+
/* Setup the default TTY line discipline. */
n_tty_init();