[U-Boot] [PATCH] Document the format of the console environment variable

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 29-03-15 17:55, Karsten Merker wrote:
> config_distro_bootcmd.h defines a common boot environment for
> multiple platforms.  Document the format of the console
> environment variable to allow the use of generic boot scripts
> on all supported platforms.
>
> Signed-off-by: Karsten Merker <merker@debian.org>

Maybe add something that distros are not encouraged to use this ?

At least on Fedora we do not want to use it, as adding
console=${console} to bootargs on systems with both video-output
(e.g. hdmi out) and a serial port will cause boot messages to
only be shown on the serial port as that is where the /dev/console
then points.

Whereas when using the devicetree chosen/stdout-path property (which
can be set either by u-boot or in the dts with the kernel),
the kernel will use both /dev/tty0 (so the hdmi out) and the serial
port pointed to by chosen/stdout as console, showing boot messages
on both, and systemd will still automatically spawn a getty on the
serial console.

Regards,

Hans




> ---
>   doc/README.distro |    9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/doc/README.distro b/doc/README.distro
> index 0308a4c..3f7ee85 100644
> --- a/doc/README.distro
> +++ b/doc/README.distro
> @@ -201,6 +201,15 @@ variables be set. Default values for these variables are often hard-coded into
>   CONFIG_EXTRA_ENV_SETTINGS in the board's U-Boot configuration file, so that
>   the user doesn't have to configure them.
>
> +console:
> +
> +  Mandatory. The default console device to be passed to the Linux kernel.
> +
> +  The console device is specified in accordance with the guidelines
> +  described in Documentation/serial-console.txt in the Linux kernel sources.
> +  If the device is a serial port, the console variable must specify the
> +  console baudrate in addition to the console device, e.g. "ttyS0,115200".
> +
>   fdt_addr:
>
>     Mandatory for any system that provides the DTB in HW (e.g. ROM) and wishes
>