Brightess on Lenovo laptop

Maybe I am in the wrong section, in that case I'll move the thread in the right one.
I'm trying to change the brightness level on my laptop (Lenovo b50 series with a intel bay trail card), but without success; I am using intel graph, loaded acpi_video, acpi_ibm, acpi_wmi, acpi_call, but anything seem to work.


# xbacklight
No outputs have backlight property

# xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1366 x 768, current 1366 x 768, maximum 1368 x 768
default connected primary 1366x768+0+0 0mm x 0mm
1366x768 0.00*
1368x768 0.00

# acpi_call -p '\VBRC' -i 10
Unknown object type '0'

# sysctl 70 -> 20

The last one seems to work, but nothing really happens.

I did not run xorg -configure after installation (but Xorg works without problems).
Is there a solution or brightness is just not supported on this terminal?
What's your graphic card? Those laptops came with Intel, NVidia and Radeon.
Most Lenovo Intel graphics laptops' backlight brightness works out of the box without X (at least with FreeBSD 11 and CURRENT).