• Len Brown's avatar
    ACPI: delete un-reliable concept of cooling mode · eaca2d3f
    Len Brown authored
    The scheme where the thermal driver displayed the
    cooling mode /proc/acpi/thermal_zone/*/cooling_mode
    was flawed in two ways.
    
    First, the success of _SCP doesn't actually mean
    that the BIOS moved any trip points.
    On many BIOS, _SCP is present, but does nothing.
    So displaying what _SCP executed actually
    was wrong more times than it was right.
    
    Second, examining the relative position of the
    trip points when the thermal_zone is added
    is insufficient -- as the BIOS reserves the right
    to change the trip points at run-time.
    
    The only reliable way for the user to determine if
    the thermal zone is in active, passive, or critical
    mode is to examine the relative position of the trip points.
    The user can do this without the kernel doing it
    for them by looking in /proc/acpi/thermal_zone/*/trip_points
    
    New contents for /proc/acpi/thermal_zone/*/cooling_mode:
    
    If _SCP available:
    "0 - Active; 1 - Passive\n"
    
    If _SCP unavailable:
    "<setting not supported>\n"
    Signed-off-by: default avatarLen Brown <len.brown@intel.com>
    eaca2d3f
thermal.c 32.9 KB