linux-kernel - Re: [PATCH] console: don't select first registered console if stdout-path used

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Date:   Sat, 26 Aug 2017 02:44:48 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] console: don't select first registered console if
 stdout-path used

On (08/25/17 16:14), Eugeniy Paltsev wrote:
> In the current implementation we take the first console that
> registers if we didn't select one.
> 
> But if we specify console via "stdout-path" property in device tree
> we don't want first console that registers here to be selected.
> Otherwise we may choose wrong console - for example if some console
> is registered earlier than console is pointed in "stdout-path"
> property because console pointed in "stdout-path" property can be add as
> preferred quite late - when it's driver is probed.
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>

hm... this is not the first time we see DT and stdout-path.
and so far it was pretty painful :) e.g. commits c6c7d83b9c9e, 05fd007e4629.

	-ss

> ---
>  kernel/printk/printk.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 512f7c2..23262c1 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -26,6 +26,7 @@
>  #include <linux/nmi.h>
>  #include <linux/module.h>
>  #include <linux/moduleparam.h>
> +#include <linux/of.h>
>  #include <linux/delay.h>
>  #include <linux/smp.h>
>  #include <linux/security.h>
> @@ -2431,6 +2432,16 @@ void register_console(struct console *newcon)
>  	if (!has_preferred || bcon || !console_drivers)
>  		has_preferred = preferred_console >= 0;
>  
> +
> +	/*
> +	 * If we specify console via "stdout-path" property in device tree
> +	 * we don't want first console that registers here to be selected.
> +	 */
> +#ifdef CONFIG_OF
> +	if (of_stdout)
> +		has_preferred = true;
> +#endif
> +
>  	/*
>  	 *	See if we want to use this console driver. If we
>  	 *	didn't select a console we take the first one
> -- 
> 2.9.3
>