Re: [PATCH] console: add new write-only option

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello,

On 10/13/20 9:59 AM, Rouven Czerwinski wrote:
> Add CONFIG_CONSOLE_WRITEONLY to configure the consoles as write-only,
> making the bootup effectively non-interactive.
> 
> Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
> ---
>  common/Kconfig          | 11 +++++++++++
>  common/console.c        |  2 +-
>  common/console_simple.c |  5 ++++-
>  common/startup.c        |  5 +++++
>  4 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/common/Kconfig b/common/Kconfig
> index 1a5bb53182..abf9b7bd73 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -775,6 +775,17 @@ config CONSOLE_ALLOW_COLOR
>  	  compile time default for colored console output. After boot it
>  	  can be controlled using global.allow_color.
>  
> +config CONSOLE_WRITEONLY
> +	prompt "Enable writeonly consoles (non-interactive)"
> +	depends on CONSOLE_FULL || CONSOLE_SIMPLE
> +	bool
> +	help
> +	  If enabled, all consoles are configured to be write-only, meaning
> +	  they will not read any input, making the console effectively
> +	  non-interactive.
> +	  CAUTION: this will also disable input devices, since they are registered as
> +	  consoles.

Did you consider having a serialX.input[1] device parameter instead?
That way you can still:

- Enable some input devices selectively (e.g. reset and power specialkeys) 
- System still has a recovery mode that can be entered if Linux
  writes a value to a SoC-internal register (reboot mode)
- have non-user-facing consoles (remoteproc with co-processor in future)

Cheers
Ahmad

> +
>  config PBL_CONSOLE
>  	depends on PBL_IMAGE
>  	depends on !CONSOLE_NONE
> diff --git a/common/console.c b/common/console.c
> index 3375ecb7e5..fb26886f8c 100644
> --- a/common/console.c
> +++ b/common/console.c
> @@ -93,7 +93,7 @@ int console_set_active(struct console_device *cdev, unsigned flag)
>  {
>  	int ret;
>  
> -	if (!cdev->getc)
> +	if (!cdev->getc || IS_ENABLED(CONFIG_CONSOLE_WRITEONLY))
>  		flag &= ~CONSOLE_STDIN;
>  	if (!cdev->putc)
>  		flag &= ~(CONSOLE_STDOUT | CONSOLE_STDERR);
> diff --git a/common/console_simple.c b/common/console_simple.c
> index 42224842c5..75257c7b08 100644
> --- a/common/console_simple.c
> +++ b/common/console_simple.c
> @@ -92,7 +92,10 @@ int console_register(struct console_device *newcdev)
>  		newcdev->setbrg(newcdev, newcdev->baudrate);
>  	}
>  
> -	newcdev->f_active = CONSOLE_STDIN | CONSOLE_STDOUT | CONSOLE_STDERR;
> +	if (IS_ENABLED(CONFIG_CONSOLE_WRITEONLY))
> +		newcdev->f_active = CONSOLE_STDOUT | CONSOLE_STDERR;
> +	else
> +		newcdev->f_active = CONSOLE_STDIN | CONSOLE_STDOUT | CONSOLE_STDERR;
>  
>  	barebox_banner();
>  
> diff --git a/common/startup.c b/common/startup.c
> index ea7ce6b8da..d7bf99df14 100644
> --- a/common/startup.c
> +++ b/common/startup.c
> @@ -253,6 +253,11 @@ enum autoboot_state do_autoboot_countdown(void)
>  
>  	menu_exists = stat(MENUFILE, &s) == 0;
>  
> +	if (IS_ENABLED(CONFIG_CONSOLE_WRITEONLY)) {
> +		printf("\nNon-interactive console, booting system\n");
> +		return autoboot_state = AUTOBOOT_BOOT;
> +	}
> +
>  	if (menu_exists) {
>  		printf("\nHit m for menu or %s to stop autoboot: ",
>  		       global_autoboot_abort_keys[global_autoboot_abort_key]);
> 

-- 
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