Hi All, Some apple laptop models have an ACPI device with a HID of APP000B and that device has an IO resource (so it does not describe the new unsupported MMIO based gmux type), but there actually is no gmux in the laptop at all. This patch-series improves the drivers/acpi/video_detect.c so that it no longer tries to use the non present gmux in this case. Note I'm still waiting for testing feedback from the reporter of this problem. But from the logs the problem is clear (the logs show: "apple_gmux: gmux device not present") and the detection code is not changed, just moved so these patches should be fine, but they can definitely use a good review. Aditya, can you perhaps test this on a model macbook which does actually use the apple-gmux driver for backlight control (assuming you have such a model) ? Rafael, since this ultimately fixes a drivers/acpi/video_detect.c bug I think it is best if you take this entire series including the platform/x86 changes. Regards, Hans Hans de Goede (3): platform/x86: apple-gmux: Move port defines to apple-gmux.h platform/x86: apple-gmux: Add apple_gmux_detect() helper ACPI: video: Fix apple gmux detection drivers/acpi/video_detect.c | 24 +------ drivers/platform/x86/apple-gmux.c | 93 +++++-------------------- include/linux/apple-gmux.h | 108 +++++++++++++++++++++++++++++- 3 files changed, 127 insertions(+), 98 deletions(-) -- 2.39.0