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 or with backlight(8) utility.

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.

POWER MANAGEMENT
The dev.asmc.%d.auto_poweron sysctl controls whether the machine automatically powers on when AC power is restored after an unclean power loss (SMC key “AUPO”). A value of 1 enables automatic power-on; 0 disables it.

RAW SMC KEY ACCESS
When the kernel is compiled with the ASMC_DEBUG option, a set of sysctl nodes is provided under dev.asmc.%d.raw for reading and writing arbitrary SMC keys by name.

dev.asmc.%d.raw.key
    Set the 4-character SMC key name to access (e.g., “AUPO”). Setting this automatically queries the key's length and type.
dev.asmc.%d.raw.value
    Read or write the key's value as a hex string.
dev.asmc.%d.raw.len
    The auto-detected value length in bytes (read-only).
dev.asmc.%d.raw.type
    The 4-character SMC type string (e.g., “ui8”, “flt”) (read-only).

Example usage:

    sysctl dev.asmc.0.raw.key=AUPO
    sysctl dev.asmc.0.raw.value
    sysctl dev.asmc.0.raw.value=01

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.

FILES
/dev/backlight/asmc0
    Keyboard backlight(8) device node.

SEE ALSO
ataidle(8) (ports/sysutils/ataidle), backlight(8), 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.