Currently, when a Mac is rebooted, the display brightness does not reflect
the level used during the previous boot. Instead, the brightness is
reset to the value last stored by macOS, causing the system to
ignore any changes made since that time.

We fix this by writing the brightness value to efivar "backlight-level"
every 300ms.

Atharva Tiwari (2):
  efi: Save Brightness using EFI on Macs
  platform/apple-gmux: use apple_brightness to save brightness to EFI

 drivers/firmware/efi/Kconfig                  | 10 ++
 drivers/firmware/efi/Makefile                 |  1 +
 drivers/firmware/efi/apple-brightness.c       | 91 +++++++++++++++++++
 drivers/platform/x86/apple-gmux.c             |  7 ++
 .../linux/platform_data/apple-brightness.h    | 21 +++++
 5 files changed, 130 insertions(+)
 create mode 100644 drivers/firmware/efi/apple-brightness.c
 create mode 100644 include/linux/platform_data/apple-brightness.h

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2.43.0