- There must be a GPU driver for these laptops somewhere?
Even if out of tree using a laptop without a GPU these days just does not give a good user experience. So fix the GPU driver to call acpi_video_register_backlight().
Note acpi_video_register_backlight() is deliberately exported without requiring the consuming out of tree kernel module to be GPL to allow this.
Other options would be:
- Add some special heuristics for Zhaoxin CPUs,
the kernel already has a CPUID match mechanism for things like this. This could potentially be combined with a DMI system-vendor check to only do this special case handling on e.g. Lenovo and Inspur laptops.
- Instead of adding the CPU-id based special case
just outright use DMI quirks. In this case lets try to use substring matches to cover multiple models with a single entry so as to not grow the quirk table too much.
Got it, thanks!
In fact, we have tried a few approaches (cmdline option, CPU-ID based quirk, and DMI quirk), and all of them work. I will sync this information with Zhaoxin to see which way they prefer.