475 lines
16 KiB
Plaintext
475 lines
16 KiB
Plaintext
Multi-monitor Mode Setting APIs
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Keith Packard, <keithp@keithp.com
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6 March 2007
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1. Introduction
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This document describes a set of mode setting APIs added in X server version
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1.3 that support multiple monitors per card. These interfaces expose the
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underlying hardware CRTC and output concepts to the xf86 DDX layer so that
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the implementation of initial server setup and mode changes through
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extensions can be shared across drivers. In addition, these new interfaces
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support a new configuration mechanism as well which allows each monitor to
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be customized separately providing a consistent cross-driver configuration
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mechanism that supports the full range of output features.
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All of the code implementing this interface can be found in hw/xfree86/modes
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in the X server sources.
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2. Overview
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This document describes both the driver API and the configuration data
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placed in xorg.conf; these are entirely separate as the driver has no
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interaction with the configuration information at all. Much of the structure
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here is cloned from the RandR extension version 1.2 additions which deal
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with the same kinds of information.
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2.1 API overview
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The mode setting API is expressed through two new driver-visible objects,
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the 'CRTC' (xf86CrtcRec) and the 'Output' (xf86OutputRec). A CRTC refers to
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hardware within the video system that can scan a subset of the framebuffer
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and generate a video signal. An Output receives that signal and transmits it
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to a monitor, projector or other device.
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The xf86CrtcRec and xf86OutputRec contain a small amount of state data
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related to the object along with a pointer to a set of functions provided by
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the driver that manipulate the object in fairly simple ways.
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To emulate older behaviour, one of the outputs is picked as the 'compat'
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output; this output changes over time as outputs are detected and used, the
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goal is to always have one 'special' output which is used for operations
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which need a single defined monitor (like XFree86-VidModeExtension mode
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setting, RandR 1.1 mode setting, DDC property setting, etc.).
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2.1.1 Output overview
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As outputs are connected to monitors, they hold a list of modes supported by
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the monitor. If the monitor and output support DDC, then the list of modes
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generally comes from the EDID data in the monitor. Otherwise, the server
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uses the standard VESA modes, pruned by monitor timing. If the configuration
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file doesn't contain monitor timing data, the server uses default timing
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information which supports 640x480, 800x600 and 1024x768 all with a 60Hz
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refresh rate.
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As hardware often limits possible configuration combinations, each output
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knows the set of CRTCs that it can be connected to as well as the set of
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other outputs which can be simutaneously connected to a CRTC.
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2.1.2 CRTC overview
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CRTCs serve only to stream frame buffer data to outputs using a mode line.
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Ideally, they would not be presented to the user at all, and in fact the
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configuration file doesn't expose them. The RandR 1.2 protocol does, but the
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hope there is that client-side applications will hide them carefully away.
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Each crtc has an associated cursor, along with the current configuration.
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All of the data needed to determine valid configurations is contained within
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the Outputs.
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2.2 Configuration overview
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As outputs drive monitors, the "Monitor" section has been repurposed to
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define their configuration. This provides for a bit more syntax than
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the large list of driver-specific options that were used in the past for
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similar configuration.
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However, the existing "Monitor" section referenced by the active "Screen"
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section no longer has any use at all; some sensible meaning for this
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parameter is needed now that a Screen can have multiple Monitors.
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3. Public Functions
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3.1 PreInit functions
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These functions should be used during the driver PreInit phase, they are
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arranged in the order they should be invoked.
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void
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xf86CrtcConfigInit (ScrnInfoPtr scrn
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const xf86CrtcConfigFuncsRec *funcs)
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This function allocates and initializes structures needed to track CRTC and
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Output state.
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void
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xf86CrtcSetSizeRange (ScrnInfoPtr scrn,
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int minWidth, int minHeight,
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int maxWidth, int maxHeight)
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This sets the range of screen sizes supported by the driver.
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xf86CrtcPtr
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xf86CrtcCreate (ScrnInfoPtr scrn,
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const xf86CrtcFuncsRec *funcs)
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Create one CRTC object. See the discussion below for a description of the
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contents of the xf86CrtcFuncsRec. Note that this is done in PreInit, so it
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should not be re-invoked at each server generation. Create one of these for
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each CRTC present in the hardware.
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xf86OutputPtr
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xf86OutputCreate (ScrnInfoPtr scrn,
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const xf86OutputFuncsRec *funcs,
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const char *name)
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Create one Output object. See the discussion below for a description of the
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contents of the xf86OutputFuncsRec. This is also called from PreInit and
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need not be re-invoked at each ScreenInit time. An Output should be created
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for every Output present in the hardware, not just for outputs which have
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detected monitors.
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Bool
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xf86OutputRename (xf86OutputPtr output, const char *name)
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If necessary, the name of an output can be changed after it is created using
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this function.
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Bool
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xf86InitialConfiguration (ScrnInfoPtr scrn, Bool canGrow)
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Using the resources provided, and the configuration specified by the user,
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this function computes an initial configuration for the server. It tries to
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enable as much hardware as possible using some fairly simple heuristics.
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The 'canGrow' parameter indicates that the frame buffer does not have a fixed
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size (fixed size frame buffers are required by XAA). When the frame buffer
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has a fixed size, the configuration selects a 'reasonablely large' frame
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buffer so that common reconfiguration options are possible. For resizable
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frame buffers, the frame buffer is set to the smallest size that encloses
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the desired configuration.
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3.2 ScreenInit functions
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These functions should be used during the driver ScreenInit phase.
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Bool
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xf86DiDGAInit (ScreenPtr screen, unsigned long dga_address)
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This function provides driver-independent accelerated DGA support for some
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of the DGA operations; using this, the driver can avoid needing to implement
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any of the rest of DGA.
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Bool
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xf86SaveScreen(ScreenPtr pScreen, int mode)
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Stick this in pScreen->SaveScreen and the core X screen saver will be
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implemented by disabling outputs and crtcs using their dpms functions.
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void
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xf86DPMSSet(ScrnInfoPtr scrn, int mode, int flags)
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Pass this function to xf86DPMSInit and all DPMS mode switching will be
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managed by using the dpms functions provided by the Outputs and CRTCs.
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Bool
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xf86CrtcScreenInit (ScreenPtr screen)
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This function completes the screen initialization process for the crtc and
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output objects. Call it near the end of the ScreenInit function, after the
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frame buffer and acceleration layers have been added.
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3.3 EnterVT functions
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Functions used during EnterVT, or whenever the current configuration needs
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to be applied to the hardware.
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Bool
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xf86SetDesiredModes (ScrnInfoPtr scrn)
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xf86InitialConfiguration selects the desired configuration at PreInit time;
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when the server finally hits ScreenInit, xf86SetDesiredModes is used by the
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driver to take that configuration and apply it to the hardware. In addition,
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successful mode selection at other times updates the configuration that will
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be used by this function, so LeaveVT/EnterVT pairs can simply invoke this
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and return to the previous configuration.
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3.4 SwitchMode functions
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Functions called from the pScrn->SwitchMode hook, which is used by the
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XFree86-VidModeExtension and the keypad mode switch commands.
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Bool
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xf86SetSingleMode (ScrnInfoPtr scrn,
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DisplayModePtr desired,
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Rotation rotation)
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This function applies the specified mode to all active outputs. Which is to
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say, it picks reasonable modes for all active outputs, attempting to get the
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screen to the specified size while not breaking anything that is currently
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working.
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3.7 get_modes functions
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Functions called during output->get_modes to help build lists of modes
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xf86MonPtr
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xf86OutputGetEDID (xf86OutputPtr output, I2CBusPtr pDDCBus)
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This returns the EDID data structure for the 'output' using the I2C bus
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'pDDCBus'. This has no effect on 'output' itself.
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void
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xf86OutputSetEDID (xf86OutputPtr output, xf86MonPtr edid_mon)
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Once the EDID data has been fetched, this call applies the EDID data to the
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output object, setting the physical size and also various properties, like
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the DDC root window property (when output is the 'compat' output), and the
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RandR 1.2 EDID output properties.
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DisplayModePtr
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xf86OutputGetEDIDModes (xf86OutputPtr output)
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Given an EDID data structure, this function computes a list of suitable
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modes. This function also applies a sequence of 'quirks' during this process
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so that the returned modes may not actually match the mode data present in
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the EDID data.
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3.6 Other functions
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These remaining functions in the API can be used by the driver as needed.
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Bool
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xf86CrtcSetMode (xf86CrtcPtr crtc, DisplayModePtr mode, Rotation rotation,
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int x, int y)
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Applies a mode to a CRTC. All of the outputs which are currently using the
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specified CRTC are included in the mode setting process. 'x' and 'y' are the
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offset within the frame buffer that the crtc is placed at. No checking is
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done in this function to ensure that the mode is usable by the active
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outputs.
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void
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xf86ProbeOutputModes (ScrnInfoPtr pScrn, int maxX, int maxY)
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This discards the mode lists for all outputs, re-detects monitor presence
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and then acquires new mode lists for all monitors which are not disconnected.
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Monitor configuration data is used to modify the mode lists returned by the
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outputs. 'maxX' and 'maxY' limit the maximum size modes that will be
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returned.
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void
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xf86SetScrnInfoModes (ScrnInfoPtr pScrn)
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This copies the 'compat' output mode list into the pScrn modes list which is
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used by the XFree86-VidModeExtension and the keypad mode switching
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operations. The current 'desired' mode for the CRTC associated with the
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'compat' output is placed first in this list to indicate the current mode.
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Usually, the driver won't need to call this function as
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xf86InitialConfiguration will do so automatically, as well as any RandR
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functions which reprobe for modes. However, if the driver reprobes for modes
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at other times using xf86ProbeOutputModes, this function needs to be called.
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Bool
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xf86DiDGAReInit (ScreenPtr pScreen)
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This is similar to xf86SetScrnInfoModes, but it applies the 'compat' output
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mode list to the set of modes advertised by the DGA extension; it needs to
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be called whenever xf86ProbeOutputModes is invoked.
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void
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xf86DisableUnusedFunctions(ScrnInfoPtr pScrn)
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After any sequence of calls using xf86CrtcSetMode, this function cleans up
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any leftover Output and CRTC objects by disabling them, saving power. It is
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safe to call this whenever the server is running as it only disables objects
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which are not currently in use.
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4. CRTC operations
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4.1 CRTC functions
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These functions provide an abstract interface for the CRTC object; most
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manipulation of the CRTC object is done through these functions.
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void
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crtc->funcs->dpms (xf86CrtcPtr crtc, int mode)
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Where 'mode' is one of DPMSModeOff, DPMSModeSuspend, DPMSModeStandby or
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DPMSModeOn. This requests that the crtc go to the specified power state.
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When changing power states, the output dpms functions are invoked before the
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crtc dpms functions.
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void
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crtc->funcs->save (xf86CrtcPtr crtc)
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void
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crtc->funcs->restore (xf86CrtcPtr crtc)
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Preserve/restore any register contents related to the CRTC. These are
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strictly a convenience for the driver writer; if the existing driver has
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fully operation save/restore functions, you need not place any additional
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code here. In particular, the server itself never uses this function.
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Bool
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crtc->funcs->lock (xf86CrtcPtr crtc)
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void
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crtc->funcs->unlock (xf86CrtcPtr crtc)
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These functions are invoked around mode setting operations; the intent is
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that DRI locking be done here to prevent DRI applications from manipulating
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the hardware while the server is busy changing the output configuration. If
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the lock function returns FALSE, the unlock function will not be invoked.
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Bool
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crtc->funcs->mode_fixup (xf86CrtcPtr crtc,
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DisplayModePtr mode,
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DisplayModePtr adjusted_mode)
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This call gives the CRTC a chance to see what mode will be set and to
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comment on the mode by changing 'adjusted_mode' as needed. This function
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shall not modify the state of the crtc hardware at all. If the CRTC cannot
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accept this mode, this function may return FALSE.
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void
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crtc->funcs->prepare (xf86CrtcPtr crtc)
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This call is made just before the mode is set to make the hardware ready for
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the operation. A usual function to perform here is to disable the crtc so
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that mode setting can occur with clocks turned off and outputs deactivated.
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void
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crtc->funcs->mode_set (xf86CrtcPtr crtc,
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DisplayModePtr mode,
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DisplayModePtr adjusted_mode)
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This function applies the specified mode (possibly adjusted by the CRTC
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and/or Outputs).
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void
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crtc->funcs->commit (xf86CrtcPtr crtc)
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Once the mode has been applied to the CRTC and Outputs, this function is
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invoked to let the hardware turn things back on.
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void
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crtc->funcs->gamma_set (xf86CrtcPtr crtc, CARD16 *red,
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CARD16 *green, CARD16 *blue, int size)
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This function adjusts the gamma ramps for the specified crtc.
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void *
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crtc->funcs->shadow_allocate (xf86CrtcPtr crtc, int width, int height)
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This function allocates frame buffer space for a shadow frame buffer. When
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allocated, the crtc must scan from the shadow instead of the main frame
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buffer. This is used for rotation. The address returned is passed to the
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shadow_create function. This function should return NULL on failure.
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PixmapPtr
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crtc->funcs->shadow_create (xf86CrtcPtr crtc, void *data,
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int width, int height)
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This function creates a pixmap object that will be used as a shadow of the
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main frame buffer for CRTCs which are rotated or reflected. 'data' is the
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value returned by shadow_allocate.
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void
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crtc->funcs->shadow_destroy (xf86CrtcPtr crtc, PixmapPtr pPixmap,
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void *data)
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Destroys any associated shadow objects. If pPixmap is NULL, then a pixmap
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was not created, but 'data' may still be non-NULL indicating that the shadow
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had been allocated.
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void
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crtc->funcs->destroy (xf86CrtcPtr crtc)
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When a CRTC is destroyed (which only happens in error cases), this function
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can clean up any driver-specific data.
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4.2 CRTC fields
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The CRTC object is not opaque; there are several fields of interest to the
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driver writer.
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struct _xf86Crtc {
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/**
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* Associated ScrnInfo
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*/
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ScrnInfoPtr scrn;
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/**
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* Active state of this CRTC
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*
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* Set when this CRTC is driving one or more outputs
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*/
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Bool enabled;
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/** Track whether cursor is within CRTC range */
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Bool cursorInRange;
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/** Track state of cursor associated with this CRTC */
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Bool cursorShown;
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/**
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* Active mode
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*
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* This reflects the mode as set in the CRTC currently
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* It will be cleared when the VT is not active or
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* during server startup
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*/
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DisplayModeRec mode;
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Rotation rotation;
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PixmapPtr rotatedPixmap;
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void *rotatedData;
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/**
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* Position on screen
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*
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* Locates this CRTC within the frame buffer
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*/
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int x, y;
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/**
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* Desired mode
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*
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* This is set to the requested mode, independent of
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* whether the VT is active. In particular, it receives
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* the startup configured mode and saves the active mode
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* on VT switch.
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*/
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DisplayModeRec desiredMode;
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Rotation desiredRotation;
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int desiredX, desiredY;
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/** crtc-specific functions */
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const xf86CrtcFuncsRec *funcs;
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/**
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* Driver private
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*
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* Holds driver-private information
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*/
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void *driver_private;
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#ifdef RANDR_12_INTERFACE
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/**
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* RandR crtc
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*
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* When RandR 1.2 is available, this
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* points at the associated crtc object
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*/
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RRCrtcPtr randr_crtc;
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#else
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void *randr_crtc;
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#endif
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};
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5. Output functions.
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6. Configuration
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Because the configuration file syntax is fixed,
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this was done by creating new "Driver" section options that hook specific
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outputs to specific "Monitor" sections in the file. The option:
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section of the form:
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Option "monitor-VGA" "My VGA Monitor"
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connects the VGA output of this driver to the "Monitor" section with
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Identifier "My VGA Monitor". All of the usual monitor options can now be
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placed in that "Monitor" section and will be applied to the VGA output
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configuration.
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