EXA driver doc cleanups and additions.
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Jesse Barnes
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@ -2,34 +2,33 @@ Adding EXA support to your X.Org video driver
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---------------------------------------------
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EXA (for EXcellent Architecture or Ex-kaa aXeleration Architecture or
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whatever) aims to extend the life of the venerable XFree86 video drivers by
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introducing hooks that they can implement to more efficiently accelerate the X
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Render extension: solid fills, blits within screen memory and to and from
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system memory, and Porter-Duff compositing and transform operations.
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introducing a new set of acceleration hooks that efficiently accelerate the X
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Render extension, including solid fills, blits within screen memory and to and
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from system memory, and Porter-Duff compositing and transform operations.
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Globals
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-------
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Configuration
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-------------
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A new config file option, AccelMethod, should be added to your driver, to allow
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the user to select between the EXA and XAA acceleration APIs.
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Some drivers implement a per-instance useEXA flag to track whether EXA is
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active or not. It can be helpful to also conditionalize XAA support with an
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ifdef so that it can easily be turned off/removed in the future.
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Setting the flag and checking for AccelMethod can be done in the driver's
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Options parsing routine.
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Global symbols
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--------------
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XF86EXA will be defined to a nonzero value if your X server codebase supports
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the EXA API. Use it to conditionalize your new EXA code if your driver is
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shared with a non-EXA codebases. If present, necessary functions, structures
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and defines will be located in "exa.h".
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AccelMethod
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-----------
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A new config file option, AccelMethod, should be used in your driver to select
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between the EXA and XAA acceleration APIs. The default should be XAA for
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6.9/7.0 drivers.
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Some drivers implement a per-instance useEXA flag to track whether EXA is
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active or not. It can be helpful to also conditionalize XAA support so that
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it can easily be turned off/removed in the future. Setting the flag and
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checking for AccelMethod can be done in the driver's Options routine (a
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friendly printf is be a nice way of letting the user know which method is in
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use).
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Core EXA functions
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------------------
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The following functions are provided, for use by your driver, to do
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allocation, initialization, version checking, etc.
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EXA library functions
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---------------------
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Use the following functions to initialize your driver's EXA hooks, check the
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version, allocate memory, etc.
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/**
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* exaGetVersion - retrieve EXA version number from server
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@ -42,13 +41,13 @@ allocation, initialization, version checking, etc.
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/**
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* exaDriverInit - tell EXA about a new EXA driver
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* @pScreen - current screen
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* @pScreenInfo - driver structure
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* @driverPtr - driver structure
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*
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* Tell EXA about the driver described by @pScreenInfo.
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*
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* Returns TRUE for success, FALSE for failure.
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*/
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Bool exaDriverInit(ScreenPtr pScreen, ExaDriverPtr pScreenInfo)
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Bool exaDriverInit(ScreenPtr pScreen, ExaDriverPtr driverPtr)
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/**
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* exaDriverFini - teardown an EXA driver
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@ -58,7 +57,6 @@ allocation, initialization, version checking, etc.
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*/
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void exaDriverFini(ScreenPtr pScreen)
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/**
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* exaOffscreenAlloc - allocate offscreen memory
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* @pScreen: current screen
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@ -118,11 +116,6 @@ allocation, initialization, version checking, etc.
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* %EXA_OFFSCREEN_PIXMAPS - offscreen pixmaps are supported
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* %EXA_OFFSCREEN_ALIGN_POT - offscreen objects must hve a power of two
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* alignment of their pitch
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*
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* This routine is just a macro, and so it can't fail (unless it causes a
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* compile failure).
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*
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* [This macro appears broken in the current tree, s/Sync/needsSync/.]
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*/
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void exaInitCard(EXADriverPtr *exa, Bool sync, CARD8 *memory_base,
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unsigned longoff_screen_base, unsigned long memory_size,
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@ -156,9 +149,6 @@ allocation, initialization, version checking, etc.
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*/
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Bool exaOffscreenInit(ScreenPtr pScreen)
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Some helper functions are also available to make common EXA related functions
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easier.
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/**
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* exaGetPixmapPitch - return the pitch for a pixmap
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* @p: pixmap
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@ -176,16 +166,21 @@ easier.
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*/
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unsigned int exaGetPixmapOffset(PixmapPtr p)
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Driver EXA routines
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-------------------
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EXA driver hooks
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----------------
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EXA requires the addition of new routines to your driver's acceleration
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implementation. The following structure defines the EXA acceleration API,
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some are required to be implemented in your driver, others are optional.
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some hooks are required to be implemented in your driver, others are optional.
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Each of these routines has an associated function pointer in the ExaAccelInfo
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structure. At a minimum, your driver must allocate an ExaDriverRec struture,
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fill out the ExaCardInfoRec member structure, and define the miminum required
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functions (described below) and hook them into the ExaAccelInfo member
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structure.
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Note that for routines that take a source and destination pixmap, the pitches
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may be different.
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typedef struct _ExaAccelInfo {
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/**
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* PrepareSolid - setup for solid fill
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* @pPixmap: Pixmap destination
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@ -340,7 +335,7 @@ may be different.
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* can't accelerate the operation (e.g. if the pixmaps are incompatible with
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* acceleration).
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*
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* Optional.
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* Optional but recommended.
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*/
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Bool (*PrepareComposite)(int op, PicturePtr pSrcPicture,
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PicturePtr pMaskPicture, PicturePtr pDstPicture,
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@ -362,7 +357,7 @@ may be different.
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*
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* Must not fail.
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*
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* Optional.
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* Optional but recommended.
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*/
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void (*Composite)(PixmapPtr pDst, int srcX, int srcY, int maskX, int maskY,
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int dstX, int dstY, int width, int height);
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@ -465,10 +460,6 @@ may be different.
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* Required.
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*/
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void (*WaitMarker)(ScreenPtr pScreen, int marker);
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} ExaAccelInfoRec, *ExaAccelInfoPtr;
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This is an extra, optional routine, used as a callback to the offscreen
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allocation function.
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/**
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* ScratchSave - save the scratch area, or just throw it away
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@ -490,24 +481,16 @@ allocation function.
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*/
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void ScratchSave(ScreenPtr pScreen, ExaOffscreenArea *area);
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EXA driver fields
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-----------------
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Each driver record structure also needs a few additional fields if EXA
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support is to be used, e.g.:
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#if XF86EXA
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/* Container structure, describes card and accel. hooks */
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ExaDriverPtr EXADriverPtr;
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#endif
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EXA initialization
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------------------
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Your driver's AccelInit routine has to initialize the EXADriverPtr if EXA
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support is enabled, with appropriate error handling (i.e. NoAccel and
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Your driver's AccelInit routine must initialize an ExaDriverRec structure if
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EXA support is enabled, with appropriate error handling (i.e. NoAccel and
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NoXvideo should be set to true if EXA fails to initialize for whatever
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reason).
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A few, card specific fields need to be initialized:
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A few, card specific fields need to be initialized (assuming your driver uses
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a variable named EXADriverPtr pointing to where your ExaDriverRec is
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allocated):
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/*
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* EXA uses memoryBase to access the framebuffer, while memorySize and
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@ -519,12 +502,13 @@ A few, card specific fields need to be initialized:
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EXADriverPtr->card.memorySize = ? /* end of offscreen memory */
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/* offset of offscreen memory relative to memoryBase */
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EXADriverPtr->card.offScreenBase = ?
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/*
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* If your offscreen memory is just after your framebuffer, which is at the
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* start of memory, it may be something like:
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* pScrn->virtualX * pScrn->virtualY * ((pScrn->bitsPerPixel * + 7) / 8)
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* should use the X value from the adjusted width based on virtualX, after
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* accounting for the accelerator's pitch alignment constraints
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* start of memory, offScreenBase may be something like:
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* pScrn->virtualX * pScrn->virtualY * ((pScrn->bitsPerPixel + 7) / 8)
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* (the + 7 / 8 causes the integer division to round up instead of
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* round down).
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*/
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/*
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@ -532,13 +516,12 @@ A few, card specific fields need to be initialized:
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* them. Not applied to all pixmaps--the visible screen is an exception,
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* and thus Prepare* acceleration hooks should test for these and fail
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* appropriately. pixmapOffsetAlign is the value that the pixmap's offset
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* from the beginning of the framebuffer must be aligned to. pixmapPitchAlign
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* is the value that the pitch of a pixmap must be aligned to (along with
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* ALIGN_POT).
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* from the beginning of the framebuffer must be aligned to.
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* pixmapPitchAlign is the value that the pitch of a pixmap must be aligned
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* to (along with ALIGN_POT).
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*/
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EXADriverPtr->card.pixmapOffsetAlign = ?
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/* also called stride */
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EXADriverPtr->card.pixmapPitchAlign = ?
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EXADriverPtr->card.pixmapPitchAlign = ? /* also called stride */
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/* Max screen size supported by the card? */
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EXADriverPtr->card.maxX = ?
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@ -575,12 +558,11 @@ out (don't forget to check for errors as that routine can fail).
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If your driver doesn't support UploadToScreen, you should allocate some
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scratch space for use by commonly used pixmaps (e.g. glyphs). Note that it's
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much better to implement UploadToScreen than to allocate scratch space, but if
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necessary allocate about as much as you'd need for a line of text.
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necessary allocate about as much as you'd need for a line of text. E.g.
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pDrv->exa_scratch = exaOffscreenAlloc(pScreen, 128 * 1024, 16, TRUE,
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ScratchSave, pDrv);
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/* Why is this required? Shouldn't exaOffscreenAlloc take care of it? */
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if(pDrv->exa_scratch) {
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pDrv->exa_scratch_next = pDrv->exa_scratch->offset;
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pDrv->EXADriverPtr->accel.UploadToScratch = UploadToScratch;
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@ -601,7 +583,7 @@ call at setup time.
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EXA teardown
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------------
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At screen close time, EXA drivers should, call exaDriverFini with their screen
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At screen close time, EXA drivers should call exaDriverFini with their screen
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pointer, free their EXADriver structure, and do any other necessary teardown.
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EXA misc.
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