From: Andre Kalb <andre.kalb@sma.de>

In case of using console="" or console=null
set console_set_on_cmdline=1 to disable "stdout-path" node from DT.

We basically need to set it every time when __add_preferred_console()
is called with parameter 'user_specified' set.
Therefore we can move setting it into a helper function that is
called from __add_preferred_console().

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andre Kalb <andre.kalb@sma.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
Changelog v1 to v2:
Move console_set_on_cmdling into separate function set_user_specified(), which is called from
__add_preferred_console().

The old patch v1 could be used to backport to stable 5.4 and lower.

Changelog v2 to v3:
Add comment to explain the less obvious behaviour.
---
 kernel/printk/printk.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 82abfaf3c2aa..e4e1a5266108 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2324,6 +2324,20 @@ asmlinkage __visible void early_printk(const char *fmt, ...)
 }
 #endif
 
+static void set_user_specified(struct console_cmdline *c, bool user_specified)
+{
+	if (!user_specified)
+		return;
+
+	/*
+	 * @c console was defined by the user on the command line.
+	 * Do not clear when added twice also by SPCR or the device tree.
+	 */
+	c->user_specified = true;
+	/* At least one console defined by the user on the command line. */
+	console_set_on_cmdline = 1;
+}
+
 static int __add_preferred_console(char *name, int idx, char *options,
 				   char *brl_options, bool user_specified)
 {
@@ -2340,8 +2354,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
 		if (strcmp(c->name, name) == 0 && c->index == idx) {
 			if (!brl_options)
 				preferred_console = i;
-			if (user_specified)
-				c->user_specified = true;
+			set_user_specified(c, user_specified);
 			return 0;
 		}
 	}
@@ -2351,7 +2364,7 @@ static int __add_preferred_console(char *name, int idx, char *options,
 		preferred_console = i;
 	strlcpy(c->name, name, sizeof(c->name));
 	c->options = options;
-	c->user_specified = user_specified;
+	set_user_specified(c, user_specified);
 	braille_set_options(c, brl_options);
 
 	c->index = idx;
@@ -2417,7 +2430,6 @@ static int __init console_setup(char *str)
 	*s = 0;
 
 	__add_preferred_console(buf, idx, options, brl_options, true);
-	console_set_on_cmdline = 1;
 	return 1;
 }
 __setup("console=", console_setup);
-- 
2.31.1

On Wed 2022-02-16 11:41:38, Andre Kalb wrote:
> From: Andre Kalb <andre.kalb@sma.de>
> 
> In case of using console="" or console=null
> set console_set_on_cmdline=1 to disable "stdout-path" node from DT.
> 
> We basically need to set it every time when __add_preferred_console()
> is called with parameter 'user_specified' set.
> Therefore we can move setting it into a helper function that is
> called from __add_preferred_console().
> 
> Suggested-by: Petr Mladek <pmladek@suse.com>
> Signed-off-by: Andre Kalb <andre.kalb@sma.de>
> Reviewed-by: Petr Mladek <pmladek@suse.com>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

The patch is comitted in printk/linux.git, branch for-5.18.

Best Regards,
Petr