[PATCH v2] efi_loader: Improve console screen clearing and reset

[Jan Kiszka]

On 09.05.22 11:05, Jan Kiszka wrote:
> On 09.05.22 10:31, Jan Kiszka wrote:
>> On 06.05.22 18:46, Heinrich Schuchardt wrote:
>>> On 5/6/22 16:50, Jan Kiszka wrote:
>>>> From: Jan Kiszka <jan.kiszka at siemens.com>
>>>>
>>>> Before clearing the screen, ensure that no previous output of firmware
>>>> or UEFI programs will be overwritten on serial devices or other
>>>> streaming consoles. This helps generating complete boot logs.
>>>>
>>>> Tested regarding multi-output against qemu-x86_defconfig.
>>>>
>>>> Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
>>>> ---
>>>>
>>>> Changes in v2:
>>>>   - rebased and tested against more scenarios, sucessfully
>>>>
>>>>   lib/efi_loader/efi_console.c | 16 +++++++++++++---
>>>>   1 file changed, 13 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
>>>> index 60a3fc85ac4..0270b20bafe 100644
>>>> --- a/lib/efi_loader/efi_console.c
>>>> +++ b/lib/efi_loader/efi_console.c
>>>> @@ -463,8 +463,18 @@ static efi_status_t EFIAPI efi_cout_set_attribute(
>>>>   static efi_status_t EFIAPI efi_cout_clear_screen(
>>>>               struct efi_simple_text_output_protocol *this)
>>>>   {
>>>> +    unsigned int row;
>>>> +
>>>>       EFI_ENTRY("%p", this);
>>>>
>>>> +    /* Avoid overwriting previous outputs on streaming consoles */
>>>> +    for (row = 1; row < efi_cout_modes[efi_con_mode.mode].rows; row++)
>>>> +        printf("\n");
>>>
>>> Unfortunately you seem to have missed to consider my review comments in
>>> https://lists.denx.de/pipermail/u-boot/2022-April/482754.html
>>
>> Nope, I address them or verified them to not apply. Please highlight
>> what I either missed or what I have to reproduce how.
>>
> 
> Ok, one thing I actually ignored as not directly related was the "cls"
> command and possibly other U-Boot internal clear-screen triggers. Those
> might be addressed similarly, but that is a different story for me. The
> purpose of this patch is to avoid that U-Boot external workload, EFI
> executables, can trigger overwriting console logs of U-Boot. If U-Boot
> decides to do that itself, or if the user does that on the command line,
> that is a different thing for me.
> 
> BTW, the bootmenu would likely be fine an in-place approach as well, but
> nothing at UART level.
> 

This one is still open. Can you please help clarifying what you would
like me to address in addition?

The patch is required for our boards which are being migrated to UEFI
and shall maintain their complete boot logs.

Thanks,
Jan

-- 
Siemens AG, Technology
Competence Center Embedded Linux