Thank you. I checked the RC5 kernel log. It confirms that the internal
panel is connected to the Intel Xe driver as eDP-1. The panel reports
DisplayPort eDP 1.4 capabilities.
The log contains no backlight, PWM, or AUX errors. However, the kernel
was started without detailed DRM logging, so it does not show whether Xe
selected PWM, standard VESA AUX, or Intel AUX brightness control.
One correction is needed for the WMI check. The previous readlink -f
command can print a path even when the WMI device is not bound to a
driver. Please run:
if [[ -L /sys/bus/wmi/devices/603E9613-EF25-4338-A3D0-C46177516DB7/driver ]];
then
readlink /sys/bus/wmi/devices/603E9613-EF25-4338-A3D0-C46177516DB7/driver
else
echo "WMI device is not bound to a driver"
fi
We can also try to enable more verbose logging by drm. To do so, you'll
need to add a boot param, which is:
drm.debug=0x1e log_buf_len=4M
To add it, you will need to do:
1. Reboot your computer and once you get to Grub (bootloader) select "Advanced
options for Ubuntu" and press ENTER. If you don't see Grub screen, reboot your
PC and hold SHIFT key in meantime during booting.
2. Highlight the entry containing "Ubuntu, with Linux 7.2.0-070200rc5-generic",
don't press ENTER.
3. Press "E" key
4. Find the long line beginning with linux. It should contain the RC5 kernel
name and parameters such as ro, quiet, and splash. For example:
linux /boot/vmlinuz-7.2.0-070200rc5-generic ... ro quiet splash
5. Move the cursor to the end of that linux line.
6. Add one space followed by:
drm.debug=0x1e log_buf_len=4M
The end of the line should look similar to:
ro quiet splash drm.debug=0x1e log_buf_len=4M
7. Press CTRL+X to boot.
8. Verify that the paremeters were applied with:
uname -r
cat /proc/cmdline
9. Repeat steps 2-4 from post #9 like you did before.
Afterwards save the diagnostic log:
sudo journalctl -b -k --no-pager > ~/brightness-rc5-drm.log and attach
it to this ticket.
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https://bugs.launchpad.net/bugs/2163244
Title:
Ubuntu 26.04 LTS -- Lenovo Yoga 7 Pro 15IPH11 Screen Brightness not
Working
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