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I use an HP laptop with an AMD R7-5800U CPU and Ubuntu 18.04, and I can't adjust display brightness with kernel versions 5.4 or 5.10.3.

I also tried other solutions, including adjust the brightness in /sys/class/backlight, and in this path, there is a directory named as api_video0.

When I change the brightness from settings, the brightness in this path is changed while the screen brightness didn't change at all.

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  • What is the model of the notebook? Some machines need to have an extra setting applied to a few files … – user1091774 Mar 6 at 5:02
  • it's the latest hp laptop in China with the latest AMD R7-5800U cpu. I found similar problems in previous 5600u cpu and it can be solved with linux kernel 5.4. – Roger1219 Mar 6 at 6:25
  • In other words - when changing brightness levels, the file /sys/class/backlight/acpi_video0/brightness changes the value written inside but the actual physical brightness does not change? – Pizza Mar 7 at 7:21
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    Is it possible that the new ubuntu system doesn't have proper driver for the new graphic card in new AMD 5800U cpu? And I search driver in AMD website. There is only a windows version driver. – Roger1219 Mar 8 at 14:14
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I'm having the same problem with the same laptop. I tried 20.04, 20.10, but none of them works. Also the USB-C and hdmi doesn't work either.

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This is a problem common with Nvidia cards. If you do have an Nvidia video card, you are going to need to load the driver.

First of all do a uname -a, it will show something like 4.15.0-142-generic, not exactly that, but something like that in the output.

After that do sudo apt install linux-headers-4.15.0-142 linux-headers-4.15.0-142-generic. It's not going to be that exact version, but the numbers have to match whatever uname -a gave you.

Then you are going to add the graphics driver repository: sudo add-apt-repository ppa:graphics-drivers/ppa

Now you can check what driver is available: sudo ubuntu-drivers devices

It should display a list and some entry is going to say "recommended" next to it. So you can go ahead and install it. sudo ubuntu-drivers autoinstall

Make sure to reboot and you should be all set. All that said, I really do hope that somebody fixes the issue that linux-headers packages are never part of any dependencies even though you can't load the video drivers correctly without them. 16.04 had a huge problem where it lost its mind every time the kernel updated. Every time there was a kernel update, before rebooting had to remember to go in and manually install the correct header set. Otherwise pain was inevitable.

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