Browse Prior Art Database

Method to force an OS with ACPI support to enter the S3 state

IP.com Disclosure Number: IPCOM000019516D
Publication Date: 2003-Sep-17
Document File: 4 page(s) / 97K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to force an operating system (OS) with advanced configuration and power interface (ACPI) support to enter the suspend-to-RAM (S3) state. Benefits include improved functionality and improved performance.

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Method to force an OS with ACPI support to enter the S3 state                

Disclosed is a method to force an operating system (OS) with advanced configuration and power interface (ACPI) support to enter the suspend-to-RAM (S3) state. Benefits include improved functionality and improved performance.

Background

The disclosed method overcomes a deficiency in operating systems that are ACPI enabled. These systems do not provide software (such as device drivers) with the capability to force the system into the S3 state.

ACPI is an open industry specification which is governed by the ACPI organization. Release 2.0.b is dated October 11, 2002. It specifically states a compliant OS must notify drivers and applications before beginning its transition into S3. However, any driver or application can reject the notification, and the OS does not enter S3. This situation may cause problems in some cases, such as when a mobile system changes ACPI system states (S states) to save battery power. Some operating systems recognize this special case and have provisions for a nonrejectable (critical) suspend when the system’s battery reports it has reached a critical level. However, sometimes this application programming interface (API) is not available to applications other than the OS. In some cases, the OS allows drivers to make a suspend request but without a guarantee that the request will be fulfilled or how long the process will take.

General description

The disclosed method forces an OS with ACPI support to enter the S3 state (or some other low power S state). To overcome the lack of the required APIs, the disclosed method is comprised of the following elements:

•         Code placed in the platform’s firmware that describes an ACPI control method battery that the OS interprets as powering the system, though no battery is actually present.

•         Code in an accompanying device driver that detects alternating current (AC) failure or resumption and causes the code in the firmware that masquerades as a battery to change the parameters of the ACPI control-method battery accordingly.

•         Change in parameters that indicate the loss of AC, which causes the ACPI control-method battery to notify the OS that is has reached a critical level (such as imminent expiration). This action triggers the OS to begin the critical (nonrejectable) suspension process.

         The disclosed method is especially useful with systems such as a desktop system with a battery-powered universal power supply (UPS). Its device driver requires a capability similar to that of a m...