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

[Alexander Graf]

On 12.10.17 00:07, Rob Clark wrote:
> 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

Yeah, those probably would need to get special cased.

> 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) ;-)

Are you sure that's what happens on a "real" computer? As far as I
remember from all ARM servers running edk2 based firmware that I've
touched so far, the default is always to display on serial *and*
graphical output at the same time.


Alex