On Monday 24 October 2022 21:58:57 Akihiko Odaki wrote:

Regarding the second limitation, I don't even understand the difference
between vendor and native. My guess is that a vendor backlight device uses
vendor-specific ACPI interface, and a native one directly uses hardware
registers. If my guess is correct, the difference between vendor and native
does not imply that both of them are likely to exist at the same time. As
the conclusion, there is no more motivation to try to de-duplicate the
vendor/native combination than to try to de-duplicate combination of devices
with a single type.

Hello! I just want to point one thing. On some Dell laptops there are
3 different ways (= 3 different APIs) how to control display backlight.
There is ACPI driver (uses ACPI), GPU/DRM driver (i915.ko; uses directly
HW) and platform vendor driver (dell-laptop.ko; uses vendor BIOS or
firmware API). Just every driver has different pre-calculated scaling
values. So sometimes user wants to choose different driver just because
it allows to set backlight level with "better" granularity. Registering
all 3 device drivers is bad as user does not want to see 3 display
panels and forcing registration of specific one without runtime option
is also bad (some of those drivers do not have to be suitable or has
worse granularity as other).