linux-kernel - Re: [PATCH v2] s390/sclp_vt220: Fix console name to match device

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Message-ID: <80735c89-a18a-5910-4e0c-f27eaa513578@de.ibm.com>
Date:   Wed, 28 Apr 2021 16:44:38 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Hendrik Brueckner <brueckner@...ux.ibm.com>,
        Valentin Vidic <vvidic@...entin-vidic.from.hr>
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, Philipp Kern <pkern@...ian.org>,
        Benjamin Zimmermann <dave@....volkswagen.com>,
        debian-s390@...ts.debian.org,
        Peter Oberparleiter <oberpar@...ux.ibm.com>
Subject: Re: [PATCH v2] s390/sclp_vt220: Fix console name to match device



On 28.04.21 15:38, Hendrik Brueckner wrote:
> Hi Valentin,
> 
> I just had the chance to look into this console topic yesterday.
> 
> On Tue, Apr 27, 2021 at 09:40:10PM +0200, Valentin Vidic wrote:
>> Console name reported in /proc/consoles:
>>
>>    ttyS1                -W- (EC p  )    4:65
> 
> It is been a while ago when working on consoles. However, consoles are
> typically devices without having a device node associated. There is special
> handling for /dev/console wrt. to the preferred console in the tty layer.
> 
> A console device might be associated with a tty device but this is not a
> requirement. For example, consider the net console that streams console
> messages thru UDP and is not associated with a tty.
> 
> Because console and tty are different devices, names can also be different
> which is, unfortunately, the case on s390.

another example is the ttyS0 console which is called sclp_line0 as a tty.
Doesnt the debian installer thus also fails when running in an LPAR?

It might still be a good idea to actually change the console name for the
ascii console as you patch does.

> Therefore my suggestion here is not derive the tty device from the name
> of the console, but rather looking at the associated tty being reported
> as major minor number in /proc/console.

So yes we should definitely try to fix the installer program as well. All other
distros seem to handle this case fine.

> 
>>
>> does not match the char device name:
>>
>>    crw--w----    1 root     root        4,  65 May 17 12:18 /dev/ttysclp0
> 
> In the example above, 4:65 excactly ends up in /dev/ttysclp0.
> 
> I am also in contact with Christian and thanks to him to try this out
> internally.  At least, there are options to bring this forward and let's
> figure out what the best solution will be.
> 
> Thanks and kind regards,
>    Hendrik
> 
h