This kernel parameter does make the backlight respond to keyboard input, as
well as manually changing the brightness values in
`/sys/class/backlight/intel_backlight/brightness`. However the behavior is
odd. Adjusting the brightness using the keyboard results in erratic changes
rather than a smooth change in brightness. The brightness settings appear
to range between 655 and 65535 in
`/sys/class/backlight/intel_backlight/brightness` when using the keyboard
keys. However, the max screen brightness appears to be at 2047 when
manually setting a brightness value in
`/sys/class/backlight/intel_backlight/brightness`.

On Thu, Feb 13, 2020 at 12:30 AM Kai-Heng Feng <email address hidden>
wrote:

> Does kernel parameter "i915.enable_dpcd_backlight=1" help?
>
> ** Changed in: linux (Ubuntu)
>        Status: Confirmed => Incomplete
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1860303
>
> Title:
>   Backlight brightness cannot be adjusted using keys
>
> Status in linux package in Ubuntu:
>   Incomplete
>
> Bug description:
>   I cannot adjust the screen brightness using the keyboard keys or
>   changing /sys/call/backlight/intel_backlight/brightness values. I've
>   only been able to adjust the backlight using xrandr.
>
>   Followed bug report on
> https://wiki.ubuntu.com/Kernel/Debugging/Backlight#Diagnostic_Techniques
> and attached files. Additional information:
>   1. echo 8 > /sys/class/backlight/intel_backlight/brightness does not
> change the screen brightness
>   2. video.use_bios_initial_backlight=0 does not enable brightness to be
> changed
>   3. Cannot login to when using kernel paramater acpi_osi=. Login does not
> work and on one boot "y"s were being continuously typed without any keys
> being depressed. It was odd.
>   4. video.use_native_backlight=1 does not enabel brightness to be changed
>   5. Created file /usr/share/X11/xorg.conf.d/80-backlight.conf and it had
> no impact
>
>   ProblemType: Bug
>   DistroRelease: Ubuntu 19.10
>   Package: linux-image-5.3.0-26-generic 5.3.0-26.28
>   ProcVersionSignature: Ubuntu 5.3.0-26.28-generic 5.3.13
>   Uname: Linux 5.3.0-26-generic x86_64
>   ApportVersion: 2.20.11-0ubuntu8.2
>   Architecture: amd64
>   AudioDevicesInUse:
>    USER        PID ACCESS COMMAND
>    /dev/snd/controlC0:  jaredy     1649 F.... pulseaudio
>    /dev/snd/pcmC0D0p:   jaredy     1649 F...m pulseaudio
>   CurrentDesktop: ubuntu:GNOME
>   Date: Sun Jan 19 19:51:45 2020
>   InstallationDate: Installed on 2020-01-03 (16 days ago)
>   InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Release amd64 (20191017)
>   MachineType: HP HP Spectre x360 Convertible 13t-aw100
>   ProcEnviron:
>    TERM=xterm-256color
>    PATH=(custom, no user)
>    XDG_RUNTIME_DIR=<set>
>    LANG=en_US.UTF-8
>    SHELL=/bin/bash
>   ProcFB: 0 i915drmfb
>   ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.3.0-26-generic
> root=UUID=5f505587-b59b-4abd-b8f2-28c04ab84c64 ro quiet splash
> acpi_backlight=vendor vt.handoff=7
>   RelatedPackageVersions:
>    linux-restricted-modules-5.3.0-26-generic N/A
>    linux-backports-modules-5.3.0-26-generic  N/A
>    linux-firmware                            1.183.3
>   SourcePackage: linux
>   UpgradeStatus: No upgrade log present (probably fresh install)
>   dmi.bios.date: 11/15/2019
>   dmi.bios.vendor: AMI
>   dmi.bios.version: F.10
>   dmi.board.asset.tag: Base Board Asset Tag
>   dmi.board.name: 86FA
>   dmi.board.vendor: HP
>   dmi.board.version: 87.43
>   dmi.chassis.type: 31
>   dmi.chassis.vendor: HP
>   dmi.chassis.version: Chassis Version
>   dmi.modalias:
> dmi:bvnAMI:bvrF.10:bd11/15/2019:svnHP:pnHPSpectrex360Convertible13t-aw100:pvr:rvnHP:rn86FA:rvr87.43:cvnHP:ct31:cvrChassisVersion:
>   dmi.product.family: 103C_5335KV HP Spectre
>   dmi.product.name: HP Spectre x360 Convertible 13t-aw100
>   dmi.product.sku: 6YG70AV
>   dmi.sys.vendor: HP
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860303/+subscriptions
>