FreeBSD/Linux Kernel Cross Reference
sys/Documentation/acpi-hotkey.txt

     driver/acpi/hotkey.c implement:
     1. /proc/acpi/hotkey/event_config 
     (event based hotkey or event config interface):
     a. add a  event based hotkey(event) : 
     echo "0:bus::action:method:num:num" > event_config
     
     b. delete a event based hotkey(event): 
     echo "1:::::num:num" > event_config
     
    c.  modify a event based hotkey(event):    
    echo "2:bus::action:method:num:num" > event_config
    
    2. /proc/acpi/hotkey/poll_config 
    (polling based hotkey or event config interface):
    a.add a polling based hotkey(event) :   
    echo "0:bus:method:action:method:num" > poll_config
    this adding command will create a proc file 
    /proc/acpi/hotkey/method, which is used to get 
    result of polling.
    
    b.delete a polling based hotkey(event):         
    echo "1:::::num" > event_config
    
    c.modify a polling based hotkey(event):    
    echo "2:bus:method:action:method:num" > poll_config
    
    3./proc/acpi/hotkey/action 
    (interface to call aml method associated with a 
    specific hotkey(event))
    echo "event_num:event_type:event_argument" > 
            /proc/acpi/hotkey/action.
    The result of the execution of this aml method is 
    attached to /proc/acpi/hotkey/poll_method, which is dynamically
    created.  Please use command "cat /proc/acpi/hotkey/polling_method" 
    to retrieve it.
    
    Note: Use cmdline "acpi_generic_hotkey" to over-ride
    platform-specific with generic driver.

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