[U-Boot] [PATCH] efi: Update README.efi to clarify build and test instructions

[Bin Meng]

Hi Igor,

On Fri, Aug 14, 2015 at 8:46 PM, Stoppa, Igor <igor.stoppa at intel.com> wrote:
> Hi Bin,
>
> On 14 August 2015 at 15:34, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Hi Igor,
>>
>> On Fri, Aug 14, 2015 at 7:46 PM, Stoppa, Igor <igor.stoppa at intel.com> wrote:
>
> [...]
>
>>> I'm still not sure I got that right, even after consulting the EFI specs.
>>
>> It is already documented, see section "Inner workings" in the same file.
>
> Yes, I did read it. That section is - unsurprisingly - written from
> the perspective of a U-Boot developer/user.

Yes, they are for hackers.

>
> However the remaining lingering doubt is: is EFI application vs
> payload something that exists only from U-Boot perspective or does the
> EFI BIOS have this concept?
> The fact that I couldn't find anything about this differentiation on
> the EFI specs probably means that it's a concept specific to U-Boot,
> but it's inferred rather than stated by the docs.
>

I did not check EFI spec, but I believe only application is mentioned
on the spec. From EFI perspective, they don't have any difference.
U-Boot EFI application and payload, they are actually the same
application type images from EFI perspective.

> [...]
>
>> This is the default naming convention that U-Boot uses. U-Boot see a
>> *board*. The efi-x86 is a *board* that represents the EFI application.
>> In the future we may add efi-arm for ARM EFI application.
>
> I see, probably this ties into my previous question about payload vs app.
>
> [...]
>
>> This is probably out of this scope for this doc. I don't know if this
>> is something special related to how the prebuilt EFI BIOS was built,
>> but I built a BIOS from the source and it worked fine. And it even
>> worked without 'fs0' and just type 'u-boot-payload.efi'. You probably
>> could ask in the edk2 community.
>
> Ok, I didn't know either if it was an issues with the specific build I used.
> I just wanted to mention it.
>
> [...]
>
>>> One more thing that I found somewhat confusing, but maybe it's just
>>> because of my very limited experience with U-Boot on x86: where is the
>>> prompt supposed to appear vs where is the logging happening?
>>>
>>
>> I don't understand. U-Boot does not require login.
>
> "logging" as: printing/showing traces

Oops, I misread. Do you mean the console output from U-Boot
application and payload?

>
>>> In some cases the logging seems to go to the screen (that's what I
>>> used), but in some other cases the logging goes to a serial port.
>>> And maybe (but I could have misunderstood) it goes also to some
>>> reserved memory area (maybe inspected with an ICE/ICD tool?).
>

Regards,
Bin