Bug#977562: systemd: Incorrect order of agetty arguments in serial-getty at ttyS0.service definition file

[Michael Biebl]

Karel,

sorry for poking you directly: Could you weigh in here?

Regards,
Michael

Am 14.01.21 um 17:21 schrieb Marcin Krol:
> 
> Well, I hoped that you'd simply change that order in the service file 
> (I'm new to this, do you expect me to produce patch or something like 
> that?). Otherwise serial comm doesn't work, at least for me.
> 
> 
> 
> 
> On 1/14/21 3:06 PM, Michael Biebl wrote:
>> Am 19.12.20 um 16:47 schrieb Andreas Henriksson:
>>> Control: tags -1 + moreinfo
>>>
>>> On Wed, Dec 16, 2020 at 11:39:06PM +0100, Michael Biebl wrote:
>>>> Am 16.12.20 um 20:49 schrieb MK:
>>>>> Package: systemd
>>>>> Version: 241-7~deb10u5
>>>>> Severity: normal
>>> [...]
>>>>> Incorrect order of arguments to agetty in the 
>>>>> serial-getty at ttyS0.service
>>>>> unit file.
>>>>>
>>>>> It is:
>>>>>
>>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud 
>>>>> 115200,38400,9600 ttyS0 xterm-256color
>>>>>
>>>>>
>>>>> While it should be like:
>>>>>
>>>>> ExecStart=/sbin/agetty --autologin root -8 --keep-baud ttyS0 115200 
>>>>> xterm-256color
>>> [...]
>>>> According to the examples in man agetty, both should work.
>>>>
>>>> Andreas, can you comment here?
>>>> If what MK is saying, should the "EXAMPLE" section in man agetty be 
>>>> updated?
>>>>
>>>
>>> I don't really have much prior knowledge about *getty, but in my past
>>> experience with other util-linux tools it is often the case that
>>> (likely for historical reasons/compatibility) the arguments that
>>> doesn't come in a dash-form is attempted to be accepted in either
>>> order based on guessing which one was specified. In my past experience
>>> something that was guessable in the past might in later years become
>>> sometimes impossible to correctly guess right, so sticking with
>>> what synopsis describes is usually the safest as far as I'm concerned.
>>>
>>> In the agetty case, the guessing is done here:
>>> https://sources.debian.org/src/util-linux/2.36.1-2/term-utils/agetty.c/#L897 
>>>
>>>
>>> is_speed basically checks if the current argument only consists of
>>> either 0-9 or ','.
>>>
>>> It is not obvious to me how it could go wrong in the example originally
>>> described in this bug report.
>>>
>>> Please also note that for example sysvinit's inittab also uses getty
>>> with arguments in both orders.
>>>
>>> Simply it should work either way.
>>>
>>> Please also note that the argument order is not the only thing changed.
>>> It was also changed from specifying 3 speeds to only 1.
>>>
>>> Maybe the real issue here is that line speed detection isn't working?
>>> I'd appreciate if the bug reporter could dive a bit deeper into the
>>> problem.
>>
>>
>> @MK any further feedback? Otherwise I would close this bug report.
>>
>> Regards,
>> Michael
>>
>>


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