I found a potential way to turn the display off fully via a software called "vbetool" and using the "vbetool dpms off" command. However there is no available openwrt package for it, and the binary I copied from arch and debian releases do not work (I tried running it in bash instead of ash).
Does anyone know the solution to this problem? How can I compile this software on openwrt? Is there any other way to mitigate the problem? Any help will be appreciated.
After some digging I found that this is a very common problem on Bay Trail Laptops/Tablets running Linux. Backlight/Brightness control does not work correctly.
I found a way to address this, by setting “video=LVDS-1:d” flag in grub config. Will try this and update when I wake up tomorrow.
probably asking a dumb question:
many laptops turn off the screen and backlight at hardware level (so this works regardless of the OS) if you close the lid. Did you check if your laptop does this? Does the screen remain on if you close the laptop screen on the keyboard?
OK. So this didn't work. Seems like all those software lvl changes rely on the driver to work properly, but it wasn't working properly, it failed to grab GPIO control for the backlight.
What I ended up doing is prying the enclosure open and disconnecting the display cable. That worked like a charm.
For anyone trying to turn their Bay Trail Tablet/Laptop into a router running openwrt, and wanting to turn off the display, you need to:
1.pry your device open
2.do not disconnect the battery cable
3.disconnect the display cable
4.assemble your device
Reason why u can't disconnect the battery:
Because when you disconnect the battery the BIOS settings will be cleared automatically, and you need to access the bios to turn off secure boot, which is very difficult with out a display.
Even if u manage to do that, on the next boot it will ask u to enter a password to ensure you want to disable secure boot. And that password is randomly generated, so u can't see it without a screen.
