Linux Receiving ACPI "Time and Alarm Device" Driver
Written by Michael Larabel in Linux Kernel on 27 March 2018 at 01:27 PM EDT. 13 Comments
LINUX KERNEL --
Another new driver coming for Linux 4.17 is a device driver implementing ACPI's specification for the Time and Alarm Device (TAD). On systems with a supported ACPI version, this can be a handy means of waking up a system with some trivial scripting.

The Linux kernel ACPI TAD driver implements the wake-up capabilities of the ACPI 6.2 specification. Via sysfs, users can manage wake-up timers of the TAD, including setting/checking/clearing timers. The timers can transition the system from S3/S4/S5 to the S0 state after a set time period elapses.

The TAD driver allows controlling all tunables from sysfs, TAD information spans platform reboots / power state transitions, and is much more featureful than say the real-time clock wake-up option you may find from your motherboard BIOS.

Linux PM subsystem maintainer Rafael Wysocki spearheaded this driver at Intel. A look at the various tunables via sysfs can be found via this documentation for those trying to grasp the scope of ACPI Time and Alarm Device.

This code is queued in Wysocki's power management -next tree for introduction with the Linux 4.17 kernel.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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