[PATCH] printk: Set console_set_on_cmdline=1 when using console="" or console=null

[PATCH] printk: Set console_set_on_cmdline=1 when using console="" or console=null

[Andre Kalb]

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.

Signed-off-by: Andre Kalb <andre.kalb@sma.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;
 		return 1;
 	}
 
-- 
2.31.1

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

[Petr Mladek]

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@sma.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

[PATCH v2] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Andre Kalb]

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>
---
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.
---
 kernel/printk/printk.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

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);
-- 
2.31.1

Re: [PATCH v2] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Sergey Senozhatsky]

On (22/02/14 14:21), Andre Kalb wrote:
> +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;
> +}

In original code we always set c->user_specified. Is it guaranteed that
->user_specified is properly initialized to 0? Maybe can do something like:

static void set_user_specified(struct console_cmdline *c, bool user_specified)
{
	c->user_specified = user_specified;

	if (!user_specified)
		return;

	console_set_on_cmdline = 1;
}

Re: [PATCH v2] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Petr Mladek]

On Tue 2022-02-15 12:15:58, Sergey Senozhatsky wrote:
> On (22/02/14 14:21), Andre Kalb wrote:
> > +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;
> > +}
> 
> In original code we always set c->user_specified. Is it guaranteed that
> ->user_specified is properly initialized to 0? Maybe can do something like:

It is guaranteed. console_cmdline is a static array initialized with
zeroes. The 2nd set_user_specified() call is done for a not-yet-used
slot in the array, so it must be zero.


> static void set_user_specified(struct console_cmdline *c, bool user_specified)
> {
> 	c->user_specified = user_specified;

This will change the behavior for the 1st set_user_specified() call.
It happens when the same console is added more times by device tree,
SPCR, and/or command line. c->user_specified must stay "true" when
at least one __add_preferred_console() call added it from the command line.

> 	if (!user_specified)
> 		return;
> 
> 	console_set_on_cmdline = 1;
> }

I agree that it is not obvious. It would make sense to add a comment
into the code. I am going to propose something in a reply to the
original post.

Best Regards,
Petr

Re: [PATCH v2] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Petr Mladek]

On Mon 2022-02-14 14:21:29, 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>
> ---
> 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.
> ---
>  kernel/printk/printk.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> 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
>  

We should add a comment explaining the less obvious behavior as
discussed in the thread. Something like:

> +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)
>  {

With the above comments:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Sergey, is it enough from your POV, please?

Best Regards,
Petr

Re: [PATCH v2] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Sergey Senozhatsky]

On (22/02/15 19:10), Petr Mladek wrote:
[..]
> We should add a comment explaining the less obvious behavior as
> discussed in the thread. Something like:
> 
> > +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)
> >  {
> 
> With the above comments:
> 
> Reviewed-by: Petr Mladek <pmladek@suse.com>
> 
> Sergey, is it enough from your POV, please?

Yes, Petr. Thank you.

Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>

[PATCH v3] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Andre Kalb]

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

Re: [PATCH v3] printk: Set console_set_on_cmdline=1 when __add_preferred_console() is called with user_specified == true

[Petr Mladek]

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