[Q] Brightness recovery CM-11

Hello Guys,
I'm trying to port CM-11 to the Samsung s5 mini.
I've built a test recovery image as described here http://wiki.cyanogenmod.org/w/Doc:_p...files_manually and then I've flashed it with odin. It works but the brightness is too low and is illegible.

How can I set the brightness for the recovery ?
Is there any property to set in the system.prop file or in the BoardConfig.mk file to set the brightness ?

Thanks
Manuel