Hi, On 10/24/22 15:14, Pali Rohár wrote: > 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). Right and that is just one example of laptops which can register both vendor + native backlight devices, which is why this whole series is a bad idea. Regards, Hans > 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).
