Proper PWM brightness for legacy OLED pannels on an Intel GPU

Reverse engineered from the Windows Driver. Thanks Lenovo for including the debugging symbols in your driver package so that even a reverse engineering illiterate like me can do it.

If your computer has an OLED screen and meets one of the following criteria, there's a chance that this driver might work for you:

Your computer is released between 2015-2018, has an Intel processor and uses its integrated GPU.

The .inf file in the Windows driver package for your computer's OLED panel contains the following text: AOR, DELVSS, BrightLevelForACL, and ACLCutoffAndDelta.

This repository contains the required kernel patches and tools to generate the firmware used by the driver.

linux-legacy-oled-brightness.patch: The patch itself. Sorry I didn't bother writing a proper commit message.

gen_panel_prop.py: Generates intel_legacy_panel_data.bin, a firmware file required by the driver.

Read this for more information, I guess.

Instructions for ThinkPad X1 Yoga 1st gen / 2nd gen:

Run gen_panel_prop.py to generate intel_legacy_panel_data.bin. Put the generated file in your firmware directory (and if needed, your initramfs).

Patch the sources for the kernel of your choice. Compile and install it.

Boot your new kernel with an additional kernel parameter i915.enable_dpcd_backlight=99. Check if it works.

Instructions for other laptops:

To be written

This repo will be updated at the same pace as my local system updates (i.e. pretty much randomly) as long as I still have the laptop and haven't been frustrated with it.