Naming inconsistency for serial device on sparc

Naming inconsistency for serial device on sparc

[John Paul Adrian Glaubitz]

Hello!

We recently ran into a regression in the debian-installer on
sparc64 which made the serial console unusable during installation.

It turned out that the regression was introduced by a change in
the rootskel package [1] and the problem is that "steal-tty" is
not able to find the active serial console and pick it up for
the installer.

After looking at the code changes, we found out that the problem is
that in the sparc64 kernel, the device names for the serial console
in /proc/consoles does not match the one under /sys:

root@landau:~# cat /proc/consoles 
ttyHV0               -W- (EC p  )    4:64
tty0                 -WU (E     )    4:1
root@landau:~#

root@landau:~# readlink /sys/dev/char/4:64
../../devices/root/f0299a70/f029b788/tty/ttyS0
root@landau:~#

Thus, any software reading /proc/consoles will not be able to figure
out what the name of the serial device is.

Is there any particular reason this device name mismatch exists or
is it just a bug we can fix?

Thanks,
Adrian

> [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug’6539
> [2] https://salsa.debian.org/installer-team/rootskel/commit/b6048aafed7d73ba42da04d6f7a798710f271384#11da32c570b25101c7d830e4fd6c254c323cddc8_21_16

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: Naming inconsistency for serial device on sparc

[David Miller]

From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Date: Sun, 14 Apr 2019 09:21:32 +0200

> Is there any particular reason this device name mismatch exists or
> is it just a bug we can fix?

It's probably been there for so long that changing it is likely to
have a risk of breaking some other piece of software.

Re: Naming inconsistency for serial device on sparc

[John Paul Adrian Glaubitz]

On 4/14/19 10:18 PM, David Miller wrote:
> From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
> Date: Sun, 14 Apr 2019 09:21:32 +0200
> 
>> Is there any particular reason this device name mismatch exists or
>> is it just a bug we can fix?
> 
> It's probably been there for so long that changing it is likely to
> have a risk of breaking some other piece of software.

Hmm, good point. We could maybe change it in the Debian kernel for testing
purposes and see if anything breaks for our users.

I'll report back.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: Naming inconsistency for serial device on sparc

[David Miller]

From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Date: Sun, 14 Apr 2019 22:25:57 +0200

> On 4/14/19 10:18 PM, David Miller wrote:
>> From: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
>> Date: Sun, 14 Apr 2019 09:21:32 +0200
>> 
>>> Is there any particular reason this device name mismatch exists or
>>> is it just a bug we can fix?
>> 
>> It's probably been there for so long that changing it is likely to
>> have a risk of breaking some other piece of software.
> 
> Hmm, good point. We could maybe change it in the Debian kernel for testing
> purposes and see if anything breaks for our users.
> 
> I'll report back.

That would cover Debian, but what about other distros whose components
are looking for the "wrong" name?

Re: Naming inconsistency for serial device on sparc

[John Paul Adrian Glaubitz]

On 4/14/19 11:13 PM, David Miller wrote:
>> Hmm, good point. We could maybe change it in the Debian kernel for testing
>> purposes and see if anything breaks for our users.
>>
>> I'll report back.
> 
> That would cover Debian, but what about other distros whose components
> are looking for the "wrong" name?

I'm not aware of any actively maintained sparc(64) Linux distributions
besides Debian and Gentoo and I know the folks from the latter, so I
could ask them for their opinion as well.

Oracle unfortunately stopped development of Oracle Linux for SPARC.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

Re: Naming inconsistency for serial device on sparc

[John Paul Adrian Glaubitz]

Hello!

On 4/14/19 11:13 PM, David Miller wrote:
>>> It's probably been there for so long that changing it is likely to
>>> have a risk of breaking some other piece of software.
>>
>> Hmm, good point. We could maybe change it in the Debian kernel for testing
>> purposes and see if anything breaks for our users.
>>
>> I'll report back.
> 
> That would cover Debian, but what about other distros whose components
> are looking for the "wrong" name?

I have talked with the Gentoo SPARC people on #gentoo-sparc OFTC now and
then don't have a particularly strong on opinion on the subject, so I think
it should be safe to fix the inconsistency bug in the driver.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913