Hi, On 3/7/23 13:27, Andy Shevchenko wrote: > On Tue, Mar 07, 2023 at 01:05:40PM +0100, Hans de Goede wrote: >> On some MacBooks both the apple_bl and the apple-gmux backlight drivers >> may be able to export a /sys/class/backlight device. >> >> To avoid having 2 backlight devices for one LCD panel until now >> the apple-gmux driver has been calling apple_bl_unregister() to move >> the apple_bl backlight device out of the way when it loads. >> >> Similar problems exist on other x86 laptops and all backlight drivers >> which may be used on x86 laptops have moved to using >> acpi_video_get_backlight_type() to determine whether they should load >> or not. >> >> Switch apple_bl to this model too, so that it is consistent with all >> the other x86 backlight drivers. >> >> Besides code-simplification and consistency this has 2 other benefits: >> >> 1) It removes a race during boot where userspace will briefly see >> an apple_bl backlight and then have it disappear again, leading to e.g.: >> https://bbs.archlinux.org/viewtopic.php?id=269920 >> >> 2) This allows user to switch between the drivers by passing >> acpi_backlight=apple_gmux or acpi_backlight=vendor on the kernel >> commandline. > > ... > >> + depends on ACPI_VIDEO=n || ACPI_VIDEO > > I'm wondering if "imply ACPI_VIDEO" (i.o.w. weak dependency) is what suitable > here. No, because then if apple_bl is builtin and acpi_video is a module we will get unresolved dependencies. The quoted bit of Kconfig magic is exactly to avoid that scenario, other combinations are fine (due to stubs in acpi/video.h when disabled). Regards, Hans
