linux 5.2.0-8.9 disabled backlight on s390x.

[Gianfranco Costamagna]

Looks like ddcci-driver-linux started to fail on s390x with the switch from kernel 5.0.0-21-generic to 5.2.0-8-generic

http://autopkgtest.ubuntu.com/packages/d/ddcci-driver-linux/eoan/s390x

According to changelog and diff:
    - [Config] CONFIG_BACKLIGHT_CLASS_DEVICE=n on s390x

from Seth Forshee.

According to the build log of ddci backlight

rm: cannot remove '.tmp_versions/ddcci-backlight.mod': No such file or directory
Makefile:227: ================= WARNING ================
Makefile:228: 'SUBDIRS' will be removed after Linux 5.3
Makefile:229: Please use 'M=' or 'KBUILD_EXTMOD' instead
Makefile:230: ==========================================
Makefile:227: ================= WARNING ================
Makefile:228: 'SUBDIRS' will be removed after Linux 5.3
Makefile:229: Please use 'M=' or 'KBUILD_EXTMOD' instead
Makefile:230: ==========================================
ERROR: "devm_backlight_device_register" [/var/lib/dkms/ddcci/0.3.2/build/ddcci-backlight/ddcci-backlight.ko] undefined!
make[3]: *** [scripts/Makefile.modpost:91: __modpost] Error 1
make[2]: *** [Makefile:1628: modules] Error 2
make[1]: *** [Makefile:37: ddcci-backlight.ko] Error 2

[Gianfranco Costamagna (costamagnagianfranco)]

We should
1) re-enable that on s390x

2) make the ddcci-driver-linux package stop providing binaries on s390x or hint the testsuite in case the user wants to dkms on previous kernels.

[Seth Forshee (sforshee)]

This driver is not useful for s390 so we should not change the kernel config just to get it building. An example was posted of how to disable a dkms build based on whether a required option is enabled the the kernel config, here:

https://bugs.launchpad.net/ubuntu/+source/acpi-call/+bug/1830040/comments/8

I think we should try something similar here.

[Paolo Pisati (p-pisati)]

Source package with fix in: https://people.canonical.com/~ppisati/lp1837073/

[Gianfranco Costamagna (costamagnagianfranco)]

thanks

[Gianfranco Costamagna (costamagnagianfranco)]

@Paolo Pisati, the fix didn't work...

[Seth Forshee (sforshee)]

We need a fix to the dkms test script. When the build is skipped due to the BUILD_EXCLUSIVE directive the tar command fails, causing the script to fail since it contains "set -eu". I'd suggest we do something like the attached.

[Gianfranco Costamagna (costamagnagianfranco)]

it is still failing...

[Seth Forshee (sforshee)]

Yes I saw, it seems to be behaving differently than when I tested those changes locally. Will try to investigate today.

[Seth Forshee (sforshee)]

I double checked that my dkms-autopkgtest updates work as I expect in an s390 instance against ddcci-driver-linux. My best guess is that autopkgtest is not using the dkms-autopktest script from the -proposed package, I'm inquiring to try and confirm this.

[Gianfranco Costamagna (costamagnagianfranco)]

sforshee now your fix has migrated but the dkms is still failing...

[Launchpad Janitor (janitor)]

This bug was fixed in the package ddcci-driver-linux - 0.3.2-2ubuntu2

---------------
ddcci-driver-linux (0.3.2-2ubuntu2) eoan; urgency=medium

  * Fix build warnings and errors with Linux 5.3 (LP: #1842671)
    - debian/patches/0003-Update-ddcci_remove_helper-prototype-for-Linux-5.3.patch
    - debian/patches/0004-Use-M-instead-of-SUBDIRS-for-specifying-module-sourc.patch

 -- Seth Forshee <email address hidden> Wed, 04 Sep 2019 09:31:18 -0500

[Seth Forshee (sforshee)]

Yes, I was talking to xnox a while back and he has in mind some changes to fix the testing. I'll check in with him about the status of those, but the issue is the testing and not ddcci-driver-linux.

[Seth Forshee (sforshee)]

In the mean time, closing the linux bug as invalid. Backlight device support is legitimately disabled in the s390x kernel configs, no kernel changes are required.

[Seth Forshee (sforshee)]

Testing has been fixed now, the most recent ddcci-driver-linux tests for s390x passed.