[maemo-leste] [PATCH] bootmenu: Allow to quit it via CTRL+C

[Heinrich Schuchardt]

On 12/26/20 11:42 PM, Pali Rohár wrote:
> On Saturday 26 December 2020 23:32:27 Pavel Machek wrote:
>> On Sat 2020-12-26 20:15:40, Pali Rohár wrote:
>>> On Saturday 26 December 2020 20:10:10 Heinrich Schuchardt wrote:
>>>> Am 26. Dezember 2020 20:03:56 MEZ schrieb "Pali Rohár" <pali at kernel.org>:
>>>>> On Saturday 26 December 2020 19:44:23 Heinrich Schuchardt wrote:
>>>>>> Am 26. Dezember 2020 19:02:25 MEZ schrieb "Pali Rohár"
>>>>> <pali at kernel.org>:
>>>>>>> When CTRL+C is pressed interrupt bootmenu and jump into U-Boot
>>>>> console.
>>>>>>> As the last entry in bootmenu is always U-Boot console just choose
>>>>> the
>>>>>>> last
>>>>>>> entry when CTRL+C is pressed.
>>>>>>>
>>>>>>> It is useful when bootmenu is part of boot process and you want to
>>>>>>> interrupt boot process by scripts which control U-Boot (serial)
>>>>>>> console.
>>>>>>
>>>>>> Wouldn't the escape key be a better choice?
>>>>>
>>>>> I can add also escape key. But has escape key stable ANSI sequence
>>>>> which
>>>>> is needed to catch? If you tell me which bytes to catch (for escape
>>>>> key)
>>>>> I will add it.
>>>>
>>>> 0x1b is Escape
>>>
>>> Does not work. 0x1b is not escape key. It is start of the ANSI escape
>>> sequence which matches also existing keys up and down.
>>
>> Unfortunately, 0x1b _is_ escape key. That is long standing bug of
>> vt100 terminal.
>
> Ok. And has xterm (or other terminals) somehow fixed it? Should we
> expect that some other terminals send something different for ESC key?
>
>> Usually timeout is used for detection. 0x1b followed by delay is
>> escape key; 0x1b followed by [ is some other key.
>
> Any idea how long timeout should be used for this detection?
>
> Heinrich wrote in his patch that sequence of 0x1b 0x1b should be handled
> by escape key. Does it mean that we need to handle both 0x1b+timeout and
> also 0x1b+0x1b as a escape key? Or we should handle 0x1b+timeout or 0x1
> followed by any non '[' character as escape key?

'man console_codes' teaches that that there are escape sequences not
starting with CSI (ESC, '[').

At 1200 baud waiting for 10 ms would be enough to differentiate between
a single key stroke an escape sequence. The 1 ms wait used in
do_conitrace() will only work at >= 19200 baud.

>
>
> Anyway, this bootmenu was initially written for Nokia N900 (used on LCD
> display with integrated keyboard) and this device does not have ESC key.
> So I would like to have CTRL+C in bootmenu working independently of ESC
> key support.
>