Hi Dennis, On Tue, Mar 06, 2018 at 12:33:23PM +0200, Andy Shevchenko wrote: > On Sun, Mar 4, 2018 at 5:28 PM, Dennis New <dennisn@xxxxxxxxxxxxxxxx> wrote: > > The /sys/class/backlight (drivers/video/backlight/apple_bl.c) > > functionality on my Apple "MacBook2,1" no longer works. It did work > > before my harddrive crashed but I no longer have those kernel .config > > files, but I'm beginning to think the problem might not be with my > > configuration. A notable difference with the way I'm running the laptop > > now is that I no longer boot "normally" off an internal sata harddrive, > > but rather using the alternative method (pressing the on button while > > holding down the Alt key) which allows me to boot off a usb stick -- > > which, I think (not sure), involves a lot more EFI stuff. > > > > I tried testing with kernels ranging from the most recent stable > > 4.15.7, 4.10, 4.8 and 4.7, and all basically behave the same way -- an > > empty /sys/class/backlight directory, and no errors in dmesg, nor when > > I load apple_bl as a module. Kudos for using this nice vintage machine. I'm not familiar with apple_bl.c but I notice that it only binds to ACPI device APP0002. Do you actually have that device in your system? It's not apparent from the information you included. It would probably be best if you could open a bugzilla on bugzilla.kernel.org and attach a full acpidump, full dmesg output and full lspci -vvvv -xxxx output. Please include "dump_apple_properties" on the command line when generating the dmesg output as I'm curious which properties are supplied on older machines and if this works at all because this might even be an EFI mixed-mode machine depending on if this is the Late 2006 or Mid 2007 version. The former used mixed-mode (64 bit CPU but 32 bit EFI) and noone ever tested whether the code to retrieve Apple EFI properties works in mixed-mode. Thanks, Lukas
