[PATCH] console: Prefer currently selected serial console as stdio device

[Simon Glass]

Hi Marek,

On Sun, 15 Mar 2026 at 17:53, Marek Vasut
<marek.vasut+renesas at mailbox.org> wrote:
>
> Adjust the scan for default console stdio device to prefer the
> currently selected serial device. This is useful in combination
> with CONFIG_SERIAL_PROBE_ALL=y, in which case the system would
> instantiate all serial devices as stdio devices in the order in
> which they are listed in control DT. The currently selected serial
> device may not be the first device listed in DT, in which case the
> current console_init_r() implementation unexpectedly switches to
> another serial console after listing stderr using "Err:" line, and
> just before showing U-Boot shell, which is not the desired behavior.
>
> The scan runs twice. The first round looks up the current serial
> console device and tests whether it is suitable as a console. If
> yes, then the scanning ends, otherwise the second round starts.
> The second round of scanning simply picks up the first suitable
> console device.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
> ---
> Cc: Alexander Sverdlin <alexander.sverdlin at siemens.com>
> Cc: Andre Przywara <andre.przywara at arm.com>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: u-boot at lists.denx.de
> ---
>  common/console.c | 38 ++++++++++++++++++++++++++++----------
>  1 file changed, 28 insertions(+), 10 deletions(-)
>
> diff --git a/common/console.c b/common/console.c
> index 48586fd2166..3de53c66094 100644
> --- a/common/console.c
> +++ b/common/console.c
> @@ -1208,17 +1208,35 @@ int console_init_r(void)
>                         outputdev = console_search_dev (DEV_FLAGS_OUTPUT, "serial");
>         }
>
> -       /* Scan devices looking for input and output devices */
> -       list_for_each(pos, list) {
> -               dev = list_entry(pos, struct stdio_dev, list);
> -
> -               if ((dev->flags & DEV_FLAGS_INPUT) && (inputdev == NULL)) {
> -                       inputdev = dev;
> -               }
> -               if ((dev->flags & DEV_FLAGS_OUTPUT) && (outputdev == NULL)) {
> -                       outputdev = dev;
> +       /*
> +        * Scan devices looking for input and output devices.
> +        * The scan runs twice. The first round looks up the current
> +        * serial console device and tests whether it is suitable as
> +        * a console. If yes, then the scanning ends, otherwise the
> +        * second round starts. The second round of scanning simply
> +        * picks up the first suitable console device. This scanning
> +        * method allows retaining the currently selected serial
> +        * console, especially in case DM contains multiple suitable
> +        * serial consoles and the currently selected one is not the
> +        * first stdio device in the list.
> +        */
> +       for (i = 0; i < 1; i++) {

It looks like it only runs once? Is this the loop you are referring to?

> +               list_for_each(pos, list) {
> +                       dev = list_entry(pos, struct stdio_dev, list);
> +                       if (!i && dev->priv != gd->cur_serial_dev)
> +                               continue;
> +
> +                       if ((dev->flags & DEV_FLAGS_INPUT) && (inputdev == NULL)) {

!inputdev

> +                               inputdev = dev;
> +                       }
> +                       if ((dev->flags & DEV_FLAGS_OUTPUT) && (outputdev == NULL)) {
> +                               outputdev = dev;
> +                       }
> +                       if (inputdev && outputdev)
> +                               break;
>                 }
> -               if(inputdev && outputdev)
> +
> +               if (inputdev && outputdev)
>                         break;
>         }

I think you could have a function like is_suitable(), call it on
gd->cur_serial_dev and then go into the loop failing that. It might
give smaller code and avoid the extra loop.

>
> --
> 2.51.0
>

Regards,
Simon