Re: [PATCH v2 3/3] multiboot2: do not set StdOut mode unconditionally

[Jan Beulich <jbeulich@xxxxxxxx>]

On 31.05.2023 12:57, Roger Pau Monné wrote:
> On Wed, Apr 05, 2023 at 12:36:55PM +0200, Jan Beulich wrote:
>> On 31.03.2023 11:59, Roger Pau Monne wrote:
>>> @@ -887,6 +881,15 @@ void __init efi_multiboot2(EFI_HANDLE ImageHandle, 
>>> EFI_SYSTEM_TABLE *SystemTable
>>>  
>>>          efi_arch_edid(gop_handle);
>>>      }
>>> +    else
>>> +    {
>>> +        /* If no GOP, init ConOut (StdOut) to the max supported size. */
>>> +        efi_console_set_mode();
>>> +
>>> +        if ( StdOut->QueryMode(StdOut, StdOut->Mode->Mode,
>>> +                               &cols, &rows) == EFI_SUCCESS )
>>> +            efi_arch_console_init(cols, rows);
>>> +    }
>>
>> Instead of making this an "else", wouldn't you better check that a
>> valid gop_mode was found? efi_find_gop_mode() can return ~0 after all.
> 
> When using vga=current gop_mode would also be ~0, in order for
> efi_set_gop_mode() to not change the current mode,

And then we'd skip efi_console_set_mode() here as well, which I think
is what we want with "vga=current"?

> I was trying to
> avoid exposing keep_current or similar extra variable to signal this.
> 
>> Furthermore, what if the active mode doesn't support text output? (I
>> consider the spec unclear in regard to whether this is possible, but
>> maybe I simply didn't find the right place stating it.)
>>
>> Finally I think efi_arch_console_init() wants calling nevertheless.
>>
>> So altogether maybe
>>
>>     if ( gop_mode == ~0 ||
>>          StdOut->QueryMode(StdOut, StdOut->Mode->Mode,
>>                            &cols, &rows) != EFI_SUCCESS )
> 
> I think it would make more sense to call efi_console_set_mode() only
> if the current StdOut mode is not valid, as anything different from
> vga=current will already force a GOP mode change.

Hmm, this may also make sense. I guess I'd like to see the combined
result to be better able to judge.

Jan