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Re: U-Boot, d-i and selecting the console device

On 2015-06-21, Karsten Merker wrote:
> If we don't pass a console variable to the kernel, d-i starts
> on the console device defined by the platform's stdout-path
> property, i.e. usually on a serial console - again bad luck
> for people having only a framebuffer console.
> If we set the console variable to tty0, d-i starts on the
> framebuffer console if it is available, or on a dummy console,
> if no framebuffer console is available. The dummy console is
> invisible, i.e. a serial-console-only user doesn't get any
> output, so bad luck for the people using a serial console
> in this case.

What about adding support in debian-installer to dsisplay on both the
serial console and framebuffer?

> AFAICS there is no way to determine the "active" console in
> u-boot and set either the u-boot console variable or the
> stdout-path property accordingly.  Even if there was such a
> mechanism, the question remains: what is the "active" console? 
> With our d-i SD-card images, the system autoboots directly into
> d-i without any user interaction required, to there is no way for
> u-boot to determine which console the user is intending to use.

Failing automatic selection, we could use u-boot's extlinux.conf support
to present the user with a menu to select between unspecified console,
console=${console}, and console=tty0...  Although I'm not sure if
variables are suported... hrm. Not a pretty user-interface, either.

Other options that come to mind are adding the ability to read a file on
the boot media and use that to determine which console to set... such as
uEnv.txt implemented in some boards. Or even just checking for the
presence of certain files on the boot media...

live well,

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