Merge tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - New option "printk.debug_non_panic_cpus" allows to store printk
   messages from non-panic CPUs during panic. It might be useful when
   panic() fails. It is disabled by default because it increases the
   chance to see the messages printed before panic() and on the
   panic-CPU.

 - New build option "CONFIG_NULL_TTY_DEFAULT_CONSOLE" allows to build
   kernel without the virtual terminal support which prefers ttynull
   over serial console.

 - Do not unblank suspended consoles.

 - Some code clean up.

* tag 'printk-for-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk/panic: Add option to allow non-panic CPUs to write to the ring buffer.
  printk: Add an option to allow ttynull to be a default console device
  printk: Check CON_SUSPEND when unblanking a console
  printk: Rename console_start to console_resume
  printk: Rename console_stop to console_suspend
  printk: Rename resume_console to console_resume_all
  printk: Rename suspend_console to console_suspend_all

2 files changed, 11 insertions, 1 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e062e6270c2a..5e351ac52cca 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5020,6 +5020,14 @@
 			Format: <bool>
 			default: 0 (auto_verbose is enabled)
 
+	printk.debug_non_panic_cpus=
+			Allows storing messages from non-panic CPUs into
+			the printk log buffer during panic(). They are
+			flushed to consoles by the panic-CPU on
+			a best-effort basis.
+			Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+			Default: disabled
+
 	printk.devkmsg={on,off,ratelimit}
 			Control writing to /dev/kmsg.
 			on - unlimited logging to /dev/kmsg from userspace
diff --git a/Documentation/admin-guide/serial-console.rst b/Documentation/admin-guide/serial-console.rst
index a3dfc2c66e01..1609e7479249 100644
--- a/Documentation/admin-guide/serial-console.rst
+++ b/Documentation/admin-guide/serial-console.rst
@@ -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.