Re: [PATCH v6 12/12] test: efi: boot: Add a test for the efi bootmeth

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 15.10.24 12:19, Mark Kettenis wrote:
>> Date: Mon, 14 Oct 2024 15:11:50 -0600
>> From: Tom Rini <trini@konsulko.com>
>>
>> On Mon, Oct 14, 2024 at 01:13:41PM -0600, Simon Glass wrote:
>>
>> [snip]
>>> Or perhaps just have a way to turn it off? I first sent this patch
>>> last November. It is just wrong to generate output like this which we
>>> don't want. There isn't even a test for it, so just add a way to
>>> disable it, and be done!
>>
>> I don't know that it's unwanted. As I'm trying to get Heinrich to
>> explain, _why_ does efi_setup_console_size need to exist, and do what it
>> does? This isn't the case of color-coding the output of tests as they
>> happen, there must be a reason we care about knowing the console size.
>> At that point we can figure out if the right answer is:
>> - Don't generate that check on serial ports, it's somewhere between
>>    misleading to wrong.
>> - text-based tests just need to expect and skip it because there's a
>>    good reason to need to know the console size and not just assume
>>    80x24.
>> - Something else we won't know until it's clearly explained why we do
>>    this.
>
> Sadly this is a misfeature of UEFI.  The EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL
> is required if console devices are supported by the UEFI
> implementation, and is built around the concept of "text mode" with a
> fixed number of character rows and columns.  That pretty much assumes
> there is some sort of terminal emulator on the other end.  And this is
> pretty much incompatible with anything that just want to log serial
> output.
>
> I think it is possible to do better though.  Instead of calling
> efi_setup_console_size() in efi_init_obj_list(), we could postpone
> this until the application makes a call that requires us to know the
> size.  This would mean that a simple EFI application that just uses
> EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.OutputString() (such as the Hello
> world EFI application or the OpenBSD EFI bootloader) wouldn't have to
> do the size query.

The implementation of EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.OutputString()
needs to know the output size to update the cursor position in

   EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.MODE.CursorColumn
   EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.MODE.CursorRow

The EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL is passed to the entry point of any
EFI application via the system table.

We could delay the invocation of efi_setup_console_size() to the launch
of the first EFI application (efi_start_image()).

Best regards

Heinrich