[U-Boot] [PATCH 06/11] efi_loader: Decouple EFI input/output from stdin/stdout

[Rob Clark]

On Wed, Oct 11, 2017 at 10:45 AM, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 10.10.17 14:23, Rob Clark wrote:
>> In some cases, it is quite useful to have (for example) EFI on screen
>> but u-boot on serial port.
>>
>> This adds two new optional environment variables, "efiin" and "efiout",
>> which can be used to set EFI console input/output independently of
>> u-boot's input/output.  If unset, EFI console will default to stdin/
>> stdout as before.
>>
>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>
> With this patch, we lose the ability to have the efi in/out go to both
> graphical and serial console, right? This is critical functionality to
> have, since we don't necessarily know which output/input a user ends up
> using.

I'll think about how to support iomux.. but some things like console
size are just not going to work properly there.  And as long as we fix
the stdout shenanigans (ie. what I was seeing w/ qemu-x86) you can
simply not set efiout var and have things working as before, so you
don't loose any existing functionality (although, like I said, if the
two different consoles have different sizes things aren't going to
work properly for anything other than simple cases).

In most cases, the display driver should be able to detect whether a
display is connected.. this is what I've done on dragonboard410c, so
if no display plugged in, 'efiout=vidconsole' fails and you fall back
to serial, else you get efi on screen like you would on a "real"
computer.  For boards that have a display driver that isn't able to do
the basic check of whether a cable is plugged in, just don't set
"efiout" (or fix the display driver) ;-)

BR,
-R


>
> Alex