linux-kernel - Re: [PATCH] printk: Set console_set_on_cmdline=1 when using console="" or console=null

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Date:   Tue, 8 Feb 2022 16:55:25 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Andre Kalb <andre.kalb@....de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: Set console_set_on_cmdline=1 when using
 console="" or console=null

On Fri 2022-01-28 00:00:52, Andre Kalb wrote:
> In case of using console="" or console=null set console_set_on_cmdline=1
> to disable chosen{ "stdout-path" } node from devicetree.
> 
> To jump out from drivers/of/base.c, line 2087 of_console_check function
> with false.

It makes sense. I would just fix it slightly different way, see below.

> Signed-off-by: Andre Kalb <andre.kalb@....de>
> ---
>  kernel/printk/printk.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 82abfaf3c2aa..df5ab35b8af2 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2385,6 +2385,7 @@ static int __init console_setup(char *str)
>  	 */
>  	if (str[0] == 0 || strcmp(str, "null") == 0) {
>  		__add_preferred_console("ttynull", 0, NULL, NULL,
> true); 
> +		console_set_on_cmdline = 1;

We basically always need to set it when __add_preferred_console() is
called with user_specified == true.

Therefore, we should move the assigment into
__add_preferred_console(). We should do something like:

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 82abfaf3c2aa..3654695ca5d2 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2324,6 +2324,15 @@ 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->user_specified = true;
+	console_set_on_cmdline = 1;
+}
+
 static int __add_preferred_console(char *name, int idx, char *options,
 				   char *brl_options, bool user_specified)
 {
@@ -2340,8 +2349,7 @@ 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 +2359,7 @@ 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 +2425,6 @@ 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);


Best Regards,
Petr