X Display Power Management Signaling (DPMS) Extension Protocol Specification Version 1.0 X Project Team Standard X Version 11, Release 6.4 Rob Lembree lembree@zk3.dec.com Digital Equipment Corporation 24 April 1996 Copyright (C) Digital Equipment Corporation, 1996 Permission to use, copy, modify, distribute, and sell this documentation for any purpose is hereby granted without fee, provided that the above copyright notice and this permission notice appear in all copies. Digital Equipment Corporation makes no representations about the suitability for any pur- pose of the information in this document. This documenta- tion is provided ``as is'' without express or implied war- ranty. 1. Overview This extension provides X Protocol control over the VESA Display Power Management Signaling (DPMS) characteristics of video boards under control of the X Window System. Traditionally, the X Window System has provided for both blanking and non-blanking screen savers. Timeouts associ- ated with these built-in screen saver mechanisms are limited to idle (dwell) time, and a change timeout that specifies the change interval for non-blanking screen savers. The United States' Environmental Protection Agency (EPA) Energy Star program requires that monitors power down after some idle time by default. While it is possible to simply overload the existing screen saver timeouts, this solution leaves the non-privileged user little to no control over the DPMS characteristics of his or her system. For example, disabling DPMS would require some unintended side effect in the core screen saver, such as disabling the changing of a non-blanking screen saver. Providing clients with this con- trol requires an extension to the core X Window System Pro- tocol, and this extension seeks to fill this gap. The design goal of the DPMS extension is to be a logical extension to the traditional screen saver. The protocol and sample implementation is designed to use the same date types and time units as the screen saver. The sample implementa- tion works independently from the screen saver so that pol- icy as it pertains to the interaction between screen saver and DPMS can be deferred to the user or screen saver appli- cation. The extension has been tested with and shown to work correctly with both the internal blanking and non-blanking screen savers, as well as with screen saver extension clients. The DPMS extension is designed to be simple, yet export suf- ficient VESA DPMS information to enable full function clients to be written. Included is the ability to sense DPMS capability, set and get DPMS timeouts, enable and dis- able individual DPMS modes, enable and disable DPMS (without destroying timeout values), and sense current DPMS on/off state and power level. There are four power levels specified by the Video Electron- ics Standards Association (VESA) Display Power Management Signaling (DPMS) standard. These are: DPMS Extension Power Levels 0 DPMSModeOn In use ----------- 1. X Window System is a trademark of X Consortium, Inc. 1 Display Power Management Signaling (DPMS) Extension 1 DPMSModeStandby Blanked, low power 2 DPMSModeSuspend Blanked, lower power 3 DPMSModeOff Shut off, awaiting activity It is logical to assume that successive DPMS modes be chronologically at the same time or later than one another, and the protocol is designed to enforce this rule. Note however that a concious decision is made to decouple the timeouts associated with screen saver from the DPMS timeouts. While it might be considered logical to require that the first non-zero DPMS timeout be greater than or equal to the screen saver timeout, this is intentionally omitted, leaving this policy decision to the user or the screen saver application. In the case of a laptop where power may be scarce, the importance of power savings should supersede the screen saver. If the laptop user plugs the unit in and power is no longer a scarce commodity, it may be decided to make DPMS less aggressive, or disable it com- pletely. 2. Requests DPMSGetVersion client_major_version: CARD16 client_minor_version: CARD16 => server_major_version: CARD16 server_minor_version: CARD16 If supplied, the client_major_version and client_minor_ver- sion indicate what version of the protocol the client wants the server to implement. The server version numbers returned indicate the protocol this extension actually sup- ports. This might not equal the version sent by the client. An implementation can (but need not) support more than one version simultaneously. The server_major_version and the server_minor_version are a mechanism to support future revi- sions of the Display Power Management Signaling protocol which may be necessary. In general, the major version would increment for incompatible changes, and the minor version would increment for small, upward-compatible changes. Servers that support the protocol defined in this document will return a server_major_version of one (1), and a server_minor_version of one (1). 2 Display Power Management Signaling (DPMS) Extension DPMSCapable => capable: BOOL This request is used to determine whether or not the cur- rently running server's devices are capable of DPMS opera- tions. The truth value of this request is implementation defined, but is generally based on the capabilities of the graphic card and monitor combination. Also, the return value in the case of heterogeneous multi-head servers is implementation defined. DPMSGetTimeouts => standby_timeout: CARD16 suspend_timeout: CARD16 off_timeout: CARD16 This request returns the current values of the DPMS timeout values. All values are in units of seconds. standby_timeout is the amount of time of inactivity before standby mode is invoked. The actual effects of this mode are implementation defined, but in the case of DPMS compliant hardware, it is implemented by shutting off the horizontal sync signal, and pulsing the vertical sync signal. Standby mode provides the quickest monitor recovery time. Note also that many monitors implement this mode identically to sus- pend mode. A value of zero indicates that this mode is dis- abled. suspend_timeout is the amount of time of inactivity before the second level of power savings is invoked. Suspend mode's physical and electrical characteristics are implementation defined, but in DPMS compliant hardware, results in the pulsing of the horizontal sync signal, and shutting off of the vertical sync signal. Suspend mode recovery is consid- ered to be slower than standby mode, but faster than off mode, however this is monitor dependent. As noted above, many monitors implement this mode identically to standby mode. A value of zero indicates that this mode is disabled. off_timeout is the amount of time of inactivity before the third and final level of power savings is invoked. Off mode's physical and electrical characteristics are implemen- tation defined, but in DPMS compliant hardware, is imple- mented by shutting off both horizontal and vertical sync signals, resulting in the power-down of the monitor. Recov- ery time is implementation dependant, but frequently is sim- ilar to the power-up time of the monitor. A value of zero 3 Display Power Management Signaling (DPMS) Extension indicates that this mode is disabled. DPMSSetTimeouts standby_timeout: CARD16 suspend_timeout: CARD16 off_timeout: CARD16 => All values are in units of seconds. standby_timeout is the amount of time of inactivity before standby mode will be invoked. This is the lightest level of power savings, and the monitor is generally immediately ready upon detection of user activity. This is most often implemented by shutting off the horizontal sync signal to the monitor. A value of zero disables this mode. The suspend_timeout specifies the amount of time of inactiv- ity before the screen is placed into suspend mode. Suspend mode is the middle level of power savings, resulting in a slightly longer recovery upon detection of activity. Sus- pend mode is most often implemented by pulsing the horizon- tal sync signal, and removing the vertical sync signal. A value of zero disables this mode. The off_timeout specifies the amount of time of inactivity before the monitor is shut off. Off mode is the deepest level of power management, resulting in the greatest power savings and the longest recovery time. Off mode is most often implemented by removing both the horizontal and verti- cal signals. A value of zero disables this mode. The values of successive power levels must be greater than or equal to the value of the previous (non-zero) level. A BadValue error is generated if an illegal combination is detected. DPMSEnable => This request enables the DPMS characteristics of the server, using the server's currently stored timeouts. If DPMS is already enabled, no change is effected. DPMSDisable => 4 Display Power Management Signaling (DPMS) Extension This request disables the DPMS characteristics of the server. It does not affect the core or extension screen savers. If DPMS is already disabled, no change is effected. This request is provided so that DPMS may be disabled with- out damaging the server's stored timeout values. DPMSForceLevel power_level: CARD16 => This request forces a specific DPMS level on the server. If DPMS is disabled, a BadMatch error is generated. If an erroneous power level is specified, a BadValue error is returned, and the error value contains the bad value. If the power level specified is already in effect, no changes occur. Power Level must be one of DPMSModeOn, DPMSMode- Standby, DPMSModeSuspend or DPMSModeOff. DPMSInfo => power_level: CARD16 state: BOOL This request returns information about the current DPMS state of the display. state is one of DPMSEnabled or DPMS- Disabled. If state is DPMSEnabled, power_level is returned as one of DPMSModeOn, DPMSModeStandby, DPMSModeSuspend or DPMSModeOff, otherwise it is undefined. 3. Events and Errors No new events or errors are defined by this extension. 4. Encoding Please refer to the X11 Protocol Encoding document as this document uses conventions established there. The name of this extension is "DPMS". DPMSGetVersion 1 CARD8 opcode 1 0 DPMS opcode 2 2 request length 2 CARD16 client_major_version 2 CARD16 client_minor_version 5 Display Power Management Signaling (DPMS) Extension => 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 length 2 CARD16 server_major_version 2 CARD16 server_minor_version 20 unused DPMSCapable 1 CARD8 opcode 1 1 DPMS opcode 2 1 request length => 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 length 1 BOOL capable 23 unused DPMSGetTimeouts 1 CARD8 opcode 1 2 DPMS opcode 2 1 request length => 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 length 2 CARD16 standby_timeout 2 CARD16 suspend_timeout 2 CARD16 off_timeout 18 unused DPMSSetTimeouts 1 CARD8 opcode 1 3 DPMS opcode 2 3 request length 2 CARD16 standby_timeout 2 CARD16 suspend_timeout 2 CARD16 off_timeout 2 unused 6 Display Power Management Signaling (DPMS) Extension => DPMSEnable 1 CARD8 opcode 1 4 DPMS opcode 2 1 request length => DPMSDisable 1 CARD8 opcode 1 5 DPMS opcode 2 1 request length => DPMSForceLevel 1 CARD8 opcode 1 6 DPMS opcode 2 2 request length 2 power_level 0 DPMSModeOn 1 DPMSModeStandby 2 DPMSModeSuspend 3 DPMSModeOff 2 unused => DPMSInfo 1 CARD8 opcode 1 7 DPMS opcode 2 1 request length => 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 length 2 power_level 0 DPMSModeOn 1 DPMSModeStandby 7 Display Power Management Signaling (DPMS) Extension 2 DPMSModeSuspend 3 DPMSModeOff 1 BOOL state 21 unused 8