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Diffstat (limited to 'xorg-server/hw/xfree86/doc/exa-driver.txt')
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diff --git a/xorg-server/hw/xfree86/doc/exa-driver.txt b/xorg-server/hw/xfree86/doc/exa-driver.txt new file mode 100644 index 000000000..048307ee7 --- /dev/null +++ b/xorg-server/hw/xfree86/doc/exa-driver.txt @@ -0,0 +1,94 @@ +Adding EXA support to your X.Org video driver +--------------------------------------------- +EXA (for EXcellent Architecture or Ex-kaa aXeleration Architecture or +whatever) aims to extend the life of the venerable XFree86 video drivers by +introducing a new set of acceleration hooks that efficiently accelerate the X +Render extension, including solid fills, blits within screen memory and to and +from system memory, and Porter-Duff compositing and transform operations. + +Configuration +------------- +A new config file option, AccelMethod, should be added to your driver, to allow +the user to select between the EXA and XAA acceleration APIs. + +Some drivers implement a per-instance useEXA flag to track whether EXA is +active or not. It can be helpful to also conditionalize XAA support with an +ifdef so that it can easily be turned off/removed in the future. + +Setting the flag and checking for AccelMethod can be done in the driver's +Options parsing routine. + +Loading EXA +------------ +EXA drivers in the XFree86 DDX should use the loadable module loader to load +the EXA core. Careful versioning allows the EXA API to be extended without +breaking the ABI for older versions of drivers. Example code for loading EXA: + +static const char *exaSymbols[] = { + "exaDriverAlloc", + "exaDriverInit", + "exaDriverFini", + "exaOffscreenAlloc", + "exaOffscreenFree", + "exaGetPixmapOffset", + "exaGetPixmapPitch", + "exaGetPixmapSize", + "exaMarkSync", + "exaWaitSync", + NULL +}; + + if (info->useEXA) { + info->exaReq.majorversion = 2; + info->exaReq.minorversion = 0; + + if (!LoadSubModule(pScrn->module, "exa", NULL, NULL, NULL, + &info->exaReq, &errmaj, &errmin)) { + LoaderErrorMsg(NULL, "exa", errmaj, errmin); + return FALSE; + } + xf86LoaderReqSymLists(exaSymbols, NULL); + } + +EXA is then initialized using exaDriverAlloc and exaDriverInit. See doxygen +documentation for getting started there. + +Further documentation +------------ +The EXA driver interface and public API is documented using doxygen in +xserver/xorg/exa/. To build the documentation, run: + doxygen -g + doxygen Doxyfile +The resulting documentation will appear an html/index.html under the current +directory. + +EXA initialization +------------------ +Your driver's AccelInit routine must initialize an ExaDriverRec structure if +EXA support is enabled, with appropriate error handling (i.e. NoAccel and +NoXvideo should be set to true if EXA fails to initialize for whatever +reason). + +The AccelInit routine also needs to make sure that there's enough offscreen +memory for certain operations to function, like Xvideo, which should advertise +a maximum size no larger than can be dealt with given the amount of offscreen +memory available. + +EXA and Xv +---------- +Video support becomes easier with EXA since AllocateFBMemory can use +exaOffscreenAlloc directly, freeing a previous area if necessary and +allocating a new one. Likewise, FreeFBMemory can call exaOffscreenFree. + +EXA teardown +------------ +At screen close time, EXA drivers should call exaDriverFini with their screen +pointer, free their EXADriver structure, and do any other necessary teardown. + +EXA misc. +--------- +In many drivers, DGA support will need to be changed to be aware of the new +EXA support. + +Send updates and corrections to Jesse Barnes <jbarnes@virtuousgeek.org> or +just check them in if you have permission. |