ASMC(4)                FreeBSD Kernel Interfaces Manual                ASMC(4)

NAME
     asmc - device driver for the Apple System Management Controller (SMC)

SYNOPSIS
     To compile this driver into the kernel, place the following line in your
     kernel configuration file:

           device asmc

     Alternatively, to load the driver as a module at boot time, place the
     following line in loader.conf(5):

           asmc_load="YES"

DESCRIPTION
     The asmc driver controls the Apple System Management Controller (SMC for
     short) found on Intel Apple systems.

     The SMC is known to be found on the following systems:

           •   MacBook
           •   MacBook Pro
           •   Intel MacMini
           •   Mac Pro
           •   MacBook Air
           •   Intel iMac

     With this driver, you can configure your keyboard backlight brightness,
     check temperatures of several sensors, check the speed of the internal
     fans and check the status of the Sudden Motion Sensor.

     Variables related to the SMC control and inspection are exported via
     sysctl(3) under the device tree dev.asmc.

KEYBOARD BACKLIGHT
     On MacBook Pro systems, you can control the keyboard brightness by
     writing a value to the dev.asmc.%d.light.control sysctl MIB.

     The following sysctl MIBs contains the raw value returned by the left and
     right light sensors: dev.asmc.%d.light.left or dev.asmc.%d.light.right.

TEMPERATURES
     The number of temperature sensors and their description varies among
     systems.  You can inspect the temperature sensors on your system by
     traversing the dev.asmc.temp sysctl MIB.

     All values are in degrees celsius.

SYSTEM FANS
     The dev.asmc.fan.%d sysctl tree contains the leaf nodes speed, safespeed,
     minspeed, maxspeed and targetspeed.  Each of these leaf nodes represent
     the current fan speed, the safest minimum fan speed, the minimum speed
     and the maximum speed respectively.

     All values are in RPM.

SUDDEN MOTION SENSOR
     The Sudden Motion Sensor (SMS for short) is a device that detects laptop
     movement and notifies the operating system via an interrupt.  The sysctl
     MIBs present under dev.asmc.sms all relate to the SMS.

     The most interesting usage of this device is to park the disk heads when
     the laptop is moved harshly.  First, you need to install ataidle(8)
     (ports/sysutils/ataidle) and then configure devd(8) the following way:

           notify 0 {
                   match "system"          "ACPI";
                   match "subsystem"       "asmc";
                   action                  "/usr/local/sbin/ataidle -s X Y";
           };

     Do not forget to change the X and Y values in the command above.

     Also, please note that parking the disk heads too many times can
     dramatically reduce your hard drive's life span.  Do not rely solely on
     the SMS to protect your hard drive: good care and common sense can
     increase your hard drive's life.

SEE ALSO
     ataidle(8) (ports/sysutils/ataidle), devd(8), sysctl(8)

HISTORY
     The asmc driver first appeared in FreeBSD 8.0.

AUTHORS
     Rui Paulo <rpaulo@FreeBSD.org> (Google Summer of Code project)

BUGS
     Support for the latest models was never tested and is most likely not
     fully working.

FreeBSD 13.1-RELEASE-p6          April 2, 2019         FreeBSD 13.1-RELEASE-p6