How to Write DirectFB gfxdrivers for Your Embedded Platform.pdf

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1、HowtoHowtoWriteDirectFBgfxdriversforYourEmbeddedPlatformTakanariHayama,HisaoMunakataandDenisOliverKropp1WhatisWhatisDirectFBDirectFB??¢ThinGraphicsLibrary–Lightweightandsmallfootprint(<700KBLibraryforSH4)Lightweightandsmallfootprint(<700KBLibraryforSH4)–N

2、otserver/clientmodellikeX11¢HardwareAbstractionLayerforHardwareGraphicsHardwareAbstractionLayerforHardwareGraphicsAcceleration–AnyygthingnotsupppportedbyyHardwarestillsupppportedbyysoftware,i.e.utilizehardwarewherepossible¢Multi-processsupport¢Andothers,e

3、.g.build-inWindowManageretc.2,3Nov2007ELC-E20072TheFirstEmbeddedChipSupportbytheMainlineDirectFB–RenesasSH77222,3Nov2007ELC-E20073df_andidf_andiandandSawManSawManrunningonrunningonSH77222,3Nov2007ELC-E20074DirectFBDirectFBSoftwareArchitectureSoftwareArchi

4、tectureforRenesasSH4SH4PlatformSH4PlatformApplicationsDirectFBgfxdriverforsystemmodulesystemmodule–Renesas’sPlatformdevmemExistingCodeLinuxKernelLinuxKernelKernelModuleCustomCodeVideoMemoryandHardwareAcceleratorHardwareHardware2,3Nov2007ELC-E20075Importan

5、tTermsinImportantTermsinDirectFBDirectFB¢Layers–Representsindependentgraphicsbuffers.MostofembeddedRepresentsindependentgraphicsbuffers.Mostofembeddeddeviceshavemorethanonelayer.Theygetlayeredwithappropriatealphablendingbyhardware,anddisplayed.¢Surface–Re

6、servedmemoryregiontoholdpixeldata.DrawingandblittingoperationinDirectFBisperformedfrom/tosurfaces.MemoryofsurfacescouldbeallocatedfromvideomemoryorMemoryofsurfacescouldbeallocatedfromvideomemoryorsystemmemorydependingonthegivenconstraints.¢PrimarySurface–

7、SpecialsrfacethatrepresentsframebfferofparticlarlaerSpecialsurfacethatrepresentsframebufferofparticularlayer.Iftheprimarysurfaceissinglebuffered,anyoperationtothisprimarysurfaceisdirectlyvisibletothescreen.2,3Nov2007ELC-E20076ConceptofLayersEachrepresents

8、layerOnthescreentheyarelayeredOnthescreentheyarelayered.17-19April2007ELC20077DirectFBDirectFBInternalArchitectureInternalArchitecture¢Modulesyouneedare:DirectFBCore–Syy(stems(opp)tional)•systems/*–GraphicsDevicesSc