Laptop monitor backlight won't turn off

[hpetrus]

There is an issue where the laptop monitor backlight won't turn off using the usual dpms methods, such as:

sleep 0.5; xset dpms force off

All the above command does is blank the screen. Backlight remains on behind it.

'xrandr --output "DP-0" --off' does turn it off, but this isn't a dpms function and is therefore inadvisable as an energy saving state, as it is a brute-force method of turning off the monitor (ie: the desktop unassigns itself from that screen completely; no keyboard or mouse event re-awakens the monitor automatically, etc.). The xset command variants (off, suspend, standby) produce the same result.

Furthermore, System Setings>Energy Saving>Screen Energy Saving produces the same result.

This is reproducible on three different Clevo/Sager/Eurocom notebooks, thus far, and has always occurred since the fresh install.

Linux Mint 18 KDE Edition

[Jesse (jesse-boyd)]

I also have this issue
with the following system
Kernel: 4.13.0-36-generic x86_64 (64 bit gcc: 5.4.0)
           Desktop: Cinnamon 3.6.7 (Gtk 3.18.9-1ubuntu3.3) Distro: Linux Mint 18.3 Sylvia
Machine: System: TOSHIBA product: Satellite L55-B v: PSKT4U-08400G
           Mobo: Type2 - Board Vendor Name1 model: Type2 - Board Product Name1 v: Type2 - Board Version
           Bios: INSYDE v: 2.00 date: 12/11/2014
CPU: Dual core Intel Core i3-4025U (-HT-MCP-) cache: 3072 KB
           flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 7582
           clock speeds: max: 1800 MHz 1: 1895 MHz 2: 1895 MHz 3: 1895 MHz 4: 1895 MHz
Graphics: Card: Intel Haswell-ULT Integrated Graphics Controller bus-ID: 00:02.0
           Display Server: X.Org 1.18.4 drivers: (unloaded: fbdev,vesa)
           Resolution: 1366x768@60.00hz, 1920x1080@60.00hz
           GLX Renderer: Mesa DRI Intel Haswell Mobile
           GLX Version: 3.0 Mesa 17.2.8 Direct Rendering: Yes
Audio: Card-1 Intel 8 Series HD Audio Controller driver: snd_hda_intel bus-ID: 00:1b.0
           Card-2 Intel Haswell-ULT HD Audio Controller
           driver: snd_hda_intel bus-ID: 00:03.0
           Sound: Advanced Linux Sound Architecture v: k4.13.0-36-generic
Network: Card-1: Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter
           driver: ath9k bus-ID: 07:00.0
           IF: wlp7s0 state: up mac: 4c:bb:58:52:e8:34
           Card-2: Realtek RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller
           driver: r8169 v: 2.3LK-NAPI port: 3000 bus-ID: 08:00.0
           IF: enp8s0 state: down mac: 2c:60:0c:1d:da:a8
Drives: HDD Total Size: 750.2GB (13.2% used)
           ID-1: /dev/sda model: TOSHIBA_MQ01ABD0 size: 750.2GB
Partition: ID-1: / size: 55G used: 8.9G (17%) fs: ext4 dev: /dev/sda5
           ID-2: /home size: 184G used: 30G (18%) fs: ext4 dev: /dev/sda7
           ID-3: swap-1 size: 12.00GB used: 0.00GB (0%) fs: swap dev: /dev/sda6
RAID: No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors: System Temperatures: cpu: 46.0C mobo: N/A
           Fan Speeds (in rpm): cpu: N/A
Info: Processes: 204 Uptime: 5 min Memory: 1234.1/5880.7MB
           Init: systemd runlevel: 5 Gcc sys: 5.4.0
           Client: Shell (bash 4.3.481) inxi: 2.2.35