Public bug reported:
Kubuntu 26.04:
With the recent 7.0.0-28.28 kernel, backlight brightness control
completely breaks and causes the screen to go to max brightness. No user
interaction in the GUI or via the brightness control keys on laptops is
able to alter mentioned brightness setting.
Steps to reproduce:
On systems with screen brightness control, update to 7.0.0-28.28 and try to
alter mentioned setting.
Expected result:
Brightness should change, either by using the GUI-based controls or the
dedicated shortcuts on most laptops ("Fn-keys" and similar setups).
Workaround:
Booting into the previous 7.0.0-27 kernel solves the issue.
Find the debug info regarding the test system attached.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Fri Jul 17 08:59:40 2026
InstallationDate: Installed on 2025-12-13 (216 days ago)
InstallationMedia: Kubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
MachineType: FUJITSU CLIENT COMPUTING LIMITED LIFEBOOK U749
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-28-generic root=UUID=xxxx ro
i8042.nomux=1 i8042.reset
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-12 (96 days ago)
dmi.bios.date: 03/28/2025
dmi.bios.release: 2.31
dmi.bios.vendor: FUJITSU // Insyde Software Corp.
dmi.bios.version: Version 2.31
dmi.board.vendor: FUJITSU
dmi.board.version: B4
dmi.chassis.type: 10
dmi.chassis.vendor: FUJITSU
dmi.chassis.version: LIFEBOOK U749
dmi.product.family: LIFEBOOK-FTS
dmi.product.name: LIFEBOOK U749
dmi.sys.vendor: FUJITSU CLIENT COMPUTING LIMITED
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
** Description changed:
Kubuntu 26.04:
With the recent 7.0.0-28.28 kernel, backlight brightness control
completely breaks and causes the screen to go to max brightness. No user
interaction in the GUI or via the brightness control keys on laptops is
able to alter mentioned brightness setting.
Steps to reproduce:
On systems with screen brightness control, update to 7.0.0-28.28 and try to
alter mentioned setting.
Expected result:
Brightness should change, either by using the GUI-based controls or the
dedicated shortcuts on most laptops ("Fn-keys" and similar setups).
Workaround:
Booting into the previous 7.0.0-27 kernel solves the issue.
Find the debug info regarding the test system attached.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
- AudioDevicesInUse:
- USER PID ACCESS COMMAND
- /dev/snd/controlC0: pascal 1687 F.... wireplumber
- /dev/snd/seq: pascal 1666 F.... pipewire
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Fri Jul 17 08:59:40 2026
InstallationDate: Installed on 2025-12-13 (216 days ago)
InstallationMedia: Kubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
MachineType: FUJITSU CLIENT COMPUTING LIMITED LIFEBOOK U749
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-28-generic
root=UUID=cb8b7c20-c2e6-44cf-a885-f622cd70b94f ro i8042.nomux=1 i8042.reset
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-12 (96 days ago)
dmi.bios.date: 03/28/2025
dmi.bios.release: 2.31
dmi.bios.vendor: FUJITSU // Insyde Software Corp.
dmi.bios.version: Version 2.31
- dmi.board.name: FJNB2CB
dmi.board.vendor: FUJITSU
dmi.board.version: B4
dmi.chassis.type: 10
dmi.chassis.vendor: FUJITSU
dmi.chassis.version: LIFEBOOK U749
dmi.modalias:
dmi:bvnFUJITSU//InsydeSoftwareCorp.:bvrVersion2.31:bd03/28/2025:br2.31:svnFUJITSUCLIENTCOMPUTINGLIMITED:pnLIFEBOOKU749:pvr10601736746:rvnFUJITSU:rnFJNB2CB:rvrB4:cvnFUJITSU:ct10:cvrLIFEBOOKU749:skuSK01:pfaLIFEBOOK-FTS:
dmi.product.family: LIFEBOOK-FTS
dmi.product.name: LIFEBOOK U749
- dmi.product.sku: SK01
- dmi.product.version: 10601736746
dmi.sys.vendor: FUJITSU CLIENT COMPUTING LIMITED
** Description changed:
Kubuntu 26.04:
With the recent 7.0.0-28.28 kernel, backlight brightness control
completely breaks and causes the screen to go to max brightness. No user
interaction in the GUI or via the brightness control keys on laptops is
able to alter mentioned brightness setting.
Steps to reproduce:
On systems with screen brightness control, update to 7.0.0-28.28 and try to
alter mentioned setting.
Expected result:
Brightness should change, either by using the GUI-based controls or the
dedicated shortcuts on most laptops ("Fn-keys" and similar setups).
Workaround:
Booting into the previous 7.0.0-27 kernel solves the issue.
Find the debug info regarding the test system attached.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Fri Jul 17 08:59:40 2026
InstallationDate: Installed on 2025-12-13 (216 days ago)
InstallationMedia: Kubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
MachineType: FUJITSU CLIENT COMPUTING LIMITED LIFEBOOK U749
ProcFB: 0 i915drmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-28-generic
root=UUID=cb8b7c20-c2e6-44cf-a885-f622cd70b94f ro i8042.nomux=1 i8042.reset
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-12 (96 days ago)
dmi.bios.date: 03/28/2025
dmi.bios.release: 2.31
dmi.bios.vendor: FUJITSU // Insyde Software Corp.
dmi.bios.version: Version 2.31
dmi.board.vendor: FUJITSU
dmi.board.version: B4
dmi.chassis.type: 10
dmi.chassis.vendor: FUJITSU
dmi.chassis.version: LIFEBOOK U749
- dmi.modalias:
dmi:bvnFUJITSU//InsydeSoftwareCorp.:bvrVersion2.31:bd03/28/2025:br2.31:svnFUJITSUCLIENTCOMPUTINGLIMITED:pnLIFEBOOKU749:pvr10601736746:rvnFUJITSU:rnFJNB2CB:rvrB4:cvnFUJITSU:ct10:cvrLIFEBOOKU749:skuSK01:pfaLIFEBOOK-FTS:
dmi.product.family: LIFEBOOK-FTS
dmi.product.name: LIFEBOOK U749
dmi.sys.vendor: FUJITSU CLIENT COMPUTING LIMITED
** Attachment removed: "WifiSyslog.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982748/+files/WifiSyslog.txt
** Description changed:
Kubuntu 26.04:
With the recent 7.0.0-28.28 kernel, backlight brightness control
completely breaks and causes the screen to go to max brightness. No user
interaction in the GUI or via the brightness control keys on laptops is
able to alter mentioned brightness setting.
Steps to reproduce:
On systems with screen brightness control, update to 7.0.0-28.28 and try to
alter mentioned setting.
Expected result:
Brightness should change, either by using the GUI-based controls or the
dedicated shortcuts on most laptops ("Fn-keys" and similar setups).
Workaround:
Booting into the previous 7.0.0-27 kernel solves the issue.
Find the debug info regarding the test system attached.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: linux-generic 7.0.0-28.28
ProcVersionSignature: Ubuntu 7.0.0-28.28-generic 7.0.12
Uname: Linux 7.0.0-28-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Fri Jul 17 08:59:40 2026
InstallationDate: Installed on 2025-12-13 (216 days ago)
InstallationMedia: Kubuntu 25.10 "Questing Quokka" - Release amd64 (20251007)
MachineType: FUJITSU CLIENT COMPUTING LIMITED LIFEBOOK U749
ProcFB: 0 i915drmfb
- ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-28-generic
root=UUID=cb8b7c20-c2e6-44cf-a885-f622cd70b94f ro i8042.nomux=1 i8042.reset
+ ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-7.0.0-28-generic root=UUID=xxxx ro
i8042.nomux=1 i8042.reset
PulseList: Error: command ['pacmd', 'list'] failed with exit code 1: No
PulseAudio daemon running, or not running as session daemon.
SourcePackage: linux
UpgradeStatus: Upgraded to resolute on 2026-04-12 (96 days ago)
dmi.bios.date: 03/28/2025
dmi.bios.release: 2.31
dmi.bios.vendor: FUJITSU // Insyde Software Corp.
dmi.bios.version: Version 2.31
dmi.board.vendor: FUJITSU
dmi.board.version: B4
dmi.chassis.type: 10
dmi.chassis.vendor: FUJITSU
dmi.chassis.version: LIFEBOOK U749
dmi.product.family: LIFEBOOK-FTS
dmi.product.name: LIFEBOOK U749
dmi.sys.vendor: FUJITSU CLIENT COMPUTING LIMITED
** Attachment removed: "AlsaInfo.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982729/+files/AlsaInfo.txt
** Attachment removed: "CRDA.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982730/+files/CRDA.txt
** Attachment removed: "acpidump.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982749/+files/acpidump.txt
** Attachment removed: "UdevDb.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982747/+files/UdevDb.txt
** Attachment removed: "RfKill.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982746/+files/RfKill.txt
** Attachment removed: "ProcModules.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982745/+files/ProcModules.txt
** Attachment removed: "ProcInterrupts.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982744/+files/ProcInterrupts.txt
** Attachment removed: "ProcEnviron.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982743/+files/ProcEnviron.txt
** Attachment removed: "ProcCpuinfoMinimal.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982742/+files/ProcCpuinfoMinimal.txt
** Attachment removed: "CurrentDmesg.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982731/+files/CurrentDmesg.txt
** Attachment removed: "Dependencies.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982732/+files/Dependencies.txt
** Attachment removed: "DpkgList.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982733/+files/DpkgList.txt
** Attachment removed: "IwDevWlp0s20f3Link.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982734/+files/IwDevWlp0s20f3Link.txt
** Attachment removed: "Lspci.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982735/+files/Lspci.txt
** Attachment removed: "Lspci-vt.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982736/+files/Lspci-vt.txt
** Attachment removed: "ProcCpuinfo.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982741/+files/ProcCpuinfo.txt
** Attachment removed: "PaInfo.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982740/+files/PaInfo.txt
** Attachment removed: "Lsusb-v.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982739/+files/Lsusb-v.txt
** Attachment removed: "Lsusb-t.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982738/+files/Lsusb-t.txt
** Attachment removed: "Lsusb.txt"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2161053/+attachment/5982737/+files/Lsusb.txt
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https://bugs.launchpad.net/bugs/2161053
Title:
Backlight brightness control breaks in 7.0.0-28.28
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