[Bug 1969434] Re: build backport-iwlwifi-dkms as linux-modules-iwlwifi-ABI

[You-Sheng Yang]

Blocked by https://bugs.launchpad.net/ubuntu/+source/backport-iwlwifi-
dkms/+bug/1970777, backport-iwlwifi-dkms 9858-0ubuntu3 fails to build
against latest linux-unstable=5.18.0-1-generic.

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https://bugs.launchpad.net/bugs/1969434

Title:
  build backport-iwlwifi-dkms as linux-modules-iwlwifi-ABI

Status in backport-iwlwifi-dkms package in Ubuntu:
  Fix Released
Status in linux package in Ubuntu:
  In Progress
Status in linux-oem-5.14 package in Ubuntu:
  Invalid
Status in linux-oem-5.17 package in Ubuntu:
  New
Status in backport-iwlwifi-dkms source package in Focal:
  New
Status in linux source package in Focal:
  Invalid
Status in linux-oem-5.14 source package in Focal:
  New
Status in linux-oem-5.17 source package in Focal:
  Invalid
Status in backport-iwlwifi-dkms source package in Jammy:
  Fix Released
Status in linux source package in Jammy:
  In Progress
Status in linux-oem-5.14 source package in Jammy:
  Invalid
Status in linux-oem-5.17 source package in Jammy:
  New

Bug description:
  [SRU Justfication]

  [Impact]

  Intel AX211 iwlwifi -64 firmware may fail to init under reboot stress,
  and -67 is immune. FW API -64 supported by oem-5.14, and -67 in v5.16.
  Not reproducible on every platform with AX211 installed, and the chances
  of such failures vary from one to another.

  [Fix]

  A few solutions were considered. The very first one is to ask Intel to
  fix -64 firmware directly, and the answer is a solid no claimed -64 is
  not the planned production version of AX211.

  It's also possible to backport FW API from v5.16, but while iwlwifi FW
  API is more or less a black box to us and the new FW APIs also depends
  on updates on the wireless stack, this is going to be very risky and
  actually we had regressions before after such backports.

  The last viable solution is to run backport-iwlwifi-dkms >= rev 8580 on
  the effected platforms. This means oem-5.14 and its migration target,
  hwe-5.15 will not be able to drive this piece of hw flawlessly without
  backport-iwlwifi-dkms installed.

  However, while we need secureboot to be enabled on these platforms,
  backport-iwlwifi-dkms must also be signed somehow. There are two
  possible method to achieve this, too. One, to prebuild this dkms as zfs
  and v4l2loopback does. However, while backport-iwlwifi-dkms generates
  kernel modules with exactly the same name as the in-tree ones, when
  prebuilt, they'll be available directly from the linux-modules package
  and therefore overrides the in-tree ones always, turning the in-tree
  driver completely useless and risk the stability of all other generic
  installations.

  The second one is to build backport-iwlwifi-dkms as nvidia graphic
  drivers in the linux-restricted-modules source package. In this way,
  affected platforms may install the corresponding packages when needed
  without interfering others. However, l-r-m is for restricted modules
  that needs special care of redistribution of its binaries, and
  backport-iwlwifi-dkms is GPL licensed.

  Here a similar but simpler process in the main kernel tree is
  re-implemented. Two additional packages,
  linux-modules-MODULE-PKGVER-ABINUM-FLAVOUR and its meta package
  linux-modules-MODULE-FLAVOUR will be created.

  [Test Case]

  Test builds:
  ./jammy/amd64/linux-modules-iwlwifi-5.15.0-27-generic_5.15.0-27.28_amd64.deb
  ./jammy/amd64/linux-modules-iwlwifi-generic_5.15.0-27.28_amd64.deb
  ./unstable/amd64/linux-modules-iwlwifi-5.17.0-8-generic_5.17.0-8.8_amd64.deb
  ./unstable/amd64/linux-modules-iwlwifi-generic_5.17.0-8.8_amd64.deb
  ./oem-5.17/amd64/linux-modules-iwlwifi-5.17.0-1003-oem_5.17.0-1003.3_amd64.deb
  ./oem-5.17/amd64/linux-modules-iwlwifi-oem_5.17.0-1003.3_amd64.deb
  ./oem-5.14/amd64/linux-modules-iwlwifi-5.14.0-1033-oem_5.14.0-1033.36_amd64.deb
  ./oem-5.14/amd64/linux-modules-iwlwifi-oem_5.14.0-1033.36_amd64.deb

  [Where problems could occur]

  The latest (9858-0ubuntu2) backport-iwlwifi-dkms/jammy actually fails
  to build under this proposed process. Debdiff attached to the same
  bug.

  Different from nvidia packages built from l-r-m, the generated package
  names do not carry an additional short version string, e.g. nvidia-410,
  as there is no such necessity to build multiple versions of iwlwifi.
  The modules are installed to /lib/modules/<kver>/kernel/iwlwifi, not
  iwlwifi-9858/.

  ========== backport-iwlwifi-dkms SRU ==========

  In order to be compiled with dkms-build in kernel source package, the
  kernel header dir will not be /lib/modules/<version>/build but a
  temporary directory. This change specifies KLIB_BUILD from dkms
  variable ${kernel_source_dir}.

  [backport-iwlwifi-dkms]

  Under some circumstances, dkms is invoked as: `/usr/sbin/dkms build
  --kernelsourcedir ...` and yet the dkms make command in this package
  has:

    MAKE="'make' -j$(num_cpu_cores) KLIB=/lib/modules/$kernelver"

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