# Help to enable backlight on AMD APU?



## Androprise (May 30, 2019)

I have recently been trying to get FreeBSD setup on my HP Pavilion 15-p051us laptop with an AMD A10-5745M APU. Everything is working except for backlight control via the acpi_video module. I found the HP Envy Touchsmart page (https://wiki.freebsd.org/Laptops/HP_Envy_TouchSmart_m6), which has the same CPU and a DSDT patch and radeonkms patch are given to fix the issue. I have made my own DSDT patch from my DSDT (I am not just using the patch from another laptop) and have eliminated error messages about _BQC functions missing in ACPI, however the brightness control still does not work, presumably because of the radeonkms driver.

I have downloaded the provided patch (have to get off archived page as links are now dead https://web.archive.org/web/20180218092110/https://wiki.freebsd.org/Laptops/HP_Envy_TouchSmart_m6) and placed it in /usr/src. I applied the patch and rebuild the drm2 module, installed it and rebooted (procedure below). The output from any of the commands below looks OK and does not give any indication that an error has occurred. 

When I reboot the driver loads (I can see the console which only works once radeonkms loades because I set "hw.syscons.disable=1" in boot/loader.conf) ,however the X11 xf86-video-ati driver does not seem to work. Upon trying to startx I get a black screen (LCD turned off completely) and see the following message in the console (which still works even after trying to startx)


```
drmn0: error: No GEM object associated to handle 0x00000300, can't create framebuffer
```

Similar errors on this forum have been solved by installing drm-kmod or drm-next-kmod or  drm-stable-kmod, however this is not an option beacuse I need the patched radeonkms driver to be able to use the backlight for this laptop. Any ideas I could try to fix this issue?

Process I used to patch and build drm2
----------------------------------------------------
sudo su
cd /usr/src
patch < radeon_backlight.patch
cd sys/modules/drm2
make -j4
make install


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