Brightness cannot be adjusted on acer aspire

On my acer aspire 5750g with intel graphics I cannot adjust brightness in kde. It worked well in 42.2
any help acknowledged
Tobias

here some additional infos:

/usr/sbin/hwinfo --gfxcard

09: PCI 02.0: 0300 VGA compatible controller (VGA)              
  [Created at pci.378]
  Unique ID: _Znp.BHyaPa4eX38
  SysFS ID: /devices/pci0000:00/0000:00:02.0
  SysFS BusID: 0000:00:02.0
  Hardware Class: graphics card
  Model: "Intel 2nd Generation Core Processor Family Integrated Graphics Controller"
  Vendor: pci 0x8086 "Intel Corporation"
  Device: pci 0x0126 "2nd Generation Core Processor Family Integrated Graphics Controller"
  SubVendor: pci 0x1025 "Acer Incorporated [ALI]"
  SubDevice: pci 0x0504 
  Revision: 0x09
  Driver: "i915"
  Driver Modules: "i915"
  Memory Range: 0xd1400000-0xd17fffff (rw,non-prefetchable)
  Memory Range: 0xc0000000-0xcfffffff (ro,non-prefetchable)
  I/O Ports: 0x3000-0x303f (rw)
  IRQ: 26 (15707 events)
  Module Alias: "pci:v00008086d00000126sv00001025sd00000504bc03sc00i00"
  Driver Info #0:
    Driver Status: i915 is active
    Driver Activation Cmd: "modprobe i915"
  Config Status: cfg=new, avail=yes, need=no, active=unknown

19: PCI 100.0: 0300 VGA compatible controller (VGA)
  [Created at pci.378]
  Unique ID: VCu0.xwI43qq8yh2
  Parent ID: vSkL.DFSSDU3IBNC
  SysFS ID: /devices/pci0000:00/0000:00:01.0/0000:01:00.0
  SysFS BusID: 0000:01:00.0
  Hardware Class: graphics card
  Model: "nVidia GF108M [GeForce GT 630M]"
  Vendor: pci 0x10de "nVidia Corporation"
  Device: pci 0x0de9 "GF108M [GeForce GT 630M]"
  SubVendor: pci 0x1025 "Acer Incorporated [ALI]"
  SubDevice: pci 0x0505 
  Revision: 0xa1
  Driver: "nouveau"
  Driver Modules: "drm"
  Memory Range: 0xd0000000-0xd0ffffff (rw,non-prefetchable)
  Memory Range: 0xa0000000-0xafffffff (ro,non-prefetchable)
  Memory Range: 0xb0000000-0xb1ffffff (ro,non-prefetchable)
  I/O Ports: 0x2000-0x2fff (rw)
  Memory Range: 0xd1000000-0xd107ffff (ro,non-prefetchable,disabled)
  IRQ: 25 (316 events)
  Module Alias: "pci:v000010DEd00000DE9sv00001025sd00000505bc03sc00i00"
  Driver Info #0:
    Driver Status: nouveau is active
    Driver Activation Cmd: "modprobe nouveau"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #8 (PCI bridge)

Primary display adapter: #9

ls -l /sys/class/backlight

lrwxrwxrwx 1 root root 0 Feb 19 22:04 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
lrwxrwxrwx 1 root root 0 Feb 19 22:04 nv_backlight -> ../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card1/card1-LVDS-2/nv_bac

cat /proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-4.4.114-42-default root=UUID=208ba184-e0ee-4f46-a3cb-74c0210b7e57 resume=/dev/disk/by-uuid/59eb1619-ca99-4b66-b2a4-3246efb30f9b splash=silent quiet showopts

xbacklight -set 20 yields
‘No outputs have backlight property’

Adding the device section in the xorg config files prevents kde-start, boot ends in a terminal.

Any clue appreciated
Thanks

And the solution is

https://forums.opensuse.org/showthread.php/527615-OpenSUSE-42-3-on-Dell-Inspiron-14R-Laptop-Screen-Brightness-not-working?highlight=Brightness

Thanks for sharing your solution.