sleeping function called from invalid context

[Neil Bird <neil@fnxweb.com>]

   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).

   This is on Fedora Core 5, kernel 2.6.17-1.2174_FC5.

-- 
[neil@fnx ~]# rm -f .signature
[neil@fnx ~]# ls -l .signature
ls: .signature: No such file or directory
[neil@fnx ~]# exit

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