An intriguing development has emerged in the Linux kernel community with the release of a post-Christmas patch series that proposes a new runtime standby ABI, reminiscent of the “Modern Standby” feature found in Microsoft Windows. This initiative was spearheaded by Antheas Kapenekakis, a notable developer with significant contributions to the Linux gaming handheld sector, including enhancements for devices like the OneXPlayer and ASUS ROG Ally.
Overview of the Proposed Runtime Standby ABI
The newly introduced patches present a more robust solution compared to previous efforts from Collabora, which focused on the “/sys/power/lps0screenoff” functionality. This feature aimed to enable user-space control over ACPI LPS0 display notifications, aligning with the specifications of Microsoft’s Modern Standby. This low-power mode in Windows 11 allows devices to maintain network connectivity while appearing to be in a sleep state, enabling instant wake-up for notifications, music playback, and other essential functions. The display may be off, yet the system remains responsive to background tasks.
Kapenekakis’s RFC patches encapsulate the essence of this innovation:
“This series introduces a new runtime standby ABI to allow firing Modern Standby firmware notifications that modify hardware appearance from userspace without suspending the kernel. This allows userspace to set the inactivity state of the device so that it looks like it is asleep (e.g., flashing the power button) while still being able to perform basic computations. The first part of this series implements the plumbing that moves the existing DSMs from being called at the end of the suspend sequence to the beginning, where they are called through a transition function. Then, the last patch exposes this transition function through /sys/power/standby to allow userspace to interact with it. In this way, the core series can be tested while not exposing the new ABI to userspace until ensured to be stable.”
For those interested in delving deeper, the RFC patch series is available for review, particularly the documentation patch that details the proposed /sys/power/standby interface. This development marks a significant step forward in enhancing the Linux experience, especially for users who rely on the seamless functionality offered by modern standby capabilities.
