Hello, 

I can't adjust the display brightness on an ASUS X551CAP laptop running 10-RELEASE (amd64).

There's a `hw.acpi.video.lcd0.brigthness' sysctl, which i can modify, but no change actual brightness can be observed:
# sysctl hw.acpi.video.lcd0.brigthness=1
hw.acpi.video.lcd0.brightness: 20 -> 1
# sysctl hw.acpi.video.lcd0.brigthness=100
hw.acpi.video.lcd0.brightness: 1 -> 100 

Nor can the 'hw.acpi.video.lcd0.active=0' be changed by using 

# sysctl hw.acpi.video.lcd0.active=1
hw.acpi.video.lcd0.active: 0 -> 0

(acpi_video.ko module was loaded while testing this, I made sure of that) 
After none of this worked I loaded the acpi_call module. A lot of the commands I threw at that had no effect or returned 'Unknown object type '0' 

(including these ones:)
#acpi_call -p '\_SB-PCI0-GFX0.DD02._BCM' -i 4
#acpi_call -p '\VBRU' '(Brightness Up)'
#acpi_call -p \VBRD' 
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BQC' 0
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BQC' 
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BCM'
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BCL'
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BCL' 10
#acpi_call -p '\-SB.PCI0.GFX0.DD02._BCL' 4



i3 window manager on Xorg
CPU: Intel(R) Celeron(R) CPU 1007U @ 1.50GHz (1496.64-M)
My make.conf file has nothing specified but:
PACKAGES=/usr/ports/packages

PS: fn+f5 and fn+f6 cannot be used to affect the brightness either and do not change the value for “ hw.acpi.video.lcd0.brigthness” either. 
I came across more people experiencing the same issue as me while on my quest to find a solution on the Internet.