Not entirely sure this is the correct place for this, but Google didn't show up anything obviously better.
I'm trying to add functionality to a kernel module which processes various input from Sony Vaio laptops (brightness and the Fn keys) by reading from ACPI. This originally did the ACPI reads during a /proc entry read (user driven).
I'm now trying to drive this read automatically by catching key press events and using that as a trigger.
However, in the input event callback, and also (as another attempt) in a tasklet process/callback the necessary call 'acpi_evaluate_object()' fails with an error “sleeping function called from invalid context”.
The kernel trace suggests this is something to do with a kmalloc() under a variant of the acpi read that involves having a 'relative ACPI path' (the string names of the registers (?) are 4-chars, not fully qualified†); I'm afraid I forget the exact function called by acpi_evaluate_object() that's listed.
Does anyone know the rules for when acpi_evaluate_object() can be called, or maybe suggest another way of getting the data? (please bear in mind I know little of ACPI!). I tried to determine the full path in case the call worked in that context; it looked like it ought to be something like _SB.xxx.xxx.GBRT instead of GBRT, and I can find this sort of hierarchy under acpi under /sys but I *can't* find the actual fields I want (e.g., GBRT) listed, even though they work (I may well be mis-interpreting this /sys tree).
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