[U-Boot] [PATCH 14/18] efi: stub: Pass EFI GOP information to U-Boot payload

[Bin Meng]

Hi Alex,

On Mon, Jun 11, 2018 at 1:52 PM, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 11.06.18 01:29, Bin Meng wrote:
>> On Mon, Jun 11, 2018 at 3:16 AM, Alexander Graf <agraf at suse.de> wrote:
>>>
>>>
>>> On 10.06.18 15:25, Bin Meng wrote:
>>>> If UEFI BIOS has the graphics output protocol (GOP), let's pass its
>>>> information to U-Boot payload so that U-Boot can utilize it (eg:
>>>> an EFI framebuffer driver).
>>>>
>>>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>>
>>> Why can't the FB drive determine all of this on its own and just fail
>>> probe if no GOP protocol can be found?
>>>
>>
>> It cannot. Once U-Boot payload is running, the boot services are gone.
>> There is no way to determine the GOP protocol.
>
> Interesting. Is there a particular reason you're not preserving boot
> services?
>

This is EFI payload support with CONFIG_EFI_STUB. Preserving boot
services is EFI application, with CONFIG_EFI_APP. For example, see
serial_efi.c which is the serial driver that uses EFI's boot services
to output characters on the serial port.

> It might be quite handy to reuse UEFI block interfaces for example. It
> might also be useful to preserve (parts of?) the memory map so we don't
> overwrite random SMM code for example.
>
> Maybe I misunderstand the purpose of the UEFI U-Boot support though ;).

Looks there is some misunderstanding around the EFI payload support.

Regards,
Bin