[Bug 2091294] Re: ddcci-dkms FTBS in Noble with linux-6.11-hwe kernel

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https://bugs.launchpad.net/bugs/2091294

Title:
  ddcci-dkms FTBS in Noble with linux-6.11-hwe kernel

Status in ddcci-driver-linux package in Ubuntu:
  In Progress
Status in ddcci-driver-linux source package in Noble:
  In Progress

Bug description:
  [ Impact ]

  The DKMS does not compile from source in Noble with kernel 6.11:

  /var/lib/dkms/ddcci/0.4.4/build/ddcci/ddcci.c:1300:27: error: initialization of ‘int (*)(struct device *, const struct device_driver *)’ from incompatible pointer type ‘int (*)(struct device *, struct device_driver *)’ [-Werror=incompatible-pointer-types]
   1300 |         .match          = ddcci_device_match,
        |                           ^~~~~~~~~~~~~~~~~~
  /var/lib/dkms/ddcci/0.4.4/build/ddcci/ddcci.c:1300:27: note: (near initialization for ‘ddcci_bus_type.match’)

  
  /var/lib/dkms/ddcci/0.4.4/build/ddcci-backlight/ddcci-backlight.c:138:10: error: ‘const struct backlight_ops’ has no member named ‘check_fb’
    138 |         .check_fb       = ddcci_backlight_check_fb,
        |          ^~~~~~~~
  /var/lib/dkms/ddcci/0.4.4/build/ddcci-backlight/ddcci-backlight.c:138:27: error: initialization of ‘bool (*)(struct backlight_device *, struct device *)’ {aka ‘_Bool (*)(struct backlight_device *, struct device *)’} from incompatible pointer type ‘int (*)(struct backlight_device *, struct fb_info *)’ [-Werror=incompatible-pointer-types]
    138 |         .check_fb       = ddcci_backlight_check_fb,
        |                           ^~~~~~~~~~~~~~~~~~~~~~~~
  /var/lib/dkms/ddcci/0.4.4/build/ddcci-backlight/ddcci-backlight.c:138:27: note: (near initialization for ‘ddcci_backlight_ops.controls_device’)

  [Test case]

  Install the latest linux-6.11 kernel on Noble:

  $ sudo add-apt-repository ppa:canonical-kernel-team/ppa
  $ sudo apt update
  $ sudo apt install linux-image-6.11.0-12-generic \
                     linux-modules-6.11.0-12-generic \
                     linux-modules-extra-6.11.0-12-generic \
                     linux-headers-6.11.0-12-generic

  Install ddcci-dkms:

  $ sudo apt install ddcci-dkms

  Load the module:

  $ sudo modprobe ddcci-backlight

  [ Fix ]

  Patch the code to properly support the new linux 6.11 ABI.

  [Regression potential]

  DDC/CI is a driver for compatible monitors and their integration into the backlight system class.
  We may experience graphical regressions in systems that are using this particular driver with kernel >= 6.11.

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