chap08-drivers

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1、CHAPTER8DeviceDriversInThisChapterÑDefiningdevicedriversÑDiscussingthedifferencebetweenarchitecture-specificandboard-specificdriversÑProvidingseveralexamplesofdifferenttypesofdevicedriversMostembeddedhardwarerequiressometypeofsoftwareinitializationandmanagement.Thesoftwarethatdire

2、ctlyinterfaceswithandcontrolsthishardwareiscalledadevicedriver.Allembeddedsystemsthatrequiresoftwarehave,attheveryleast,devicedriversoftwareintheirsystemsoftwarelayer.Devicedriversarethesoftwarelibrariesthatinitializethehardware,andmanageaccesstothehardwarebyhigherlayersofsoftware

3、.Devicedriversaretheliai-sonbetweenthehardwareandtheoperatingsystem,middleware,andapplicationlayers.AplicationSpoftwareLayerAplicationSpoftwareLayerAplicationSpoftwareLayerSystemSoftwareLayerSystemSoftwareLayerSystemSoftwareLayerDeviceDriverLayerMiddlewareLayerOperatingSystemLayer

4、DeviceDriverLayerDeviceDriverLayerHardwareLayerHardwareLayerHardwareLayerFigure8-1:EmbeddedSystemsModelanddevicedrivers311Chapter8Thetypesofhardwarecomponentsneedingthesupportofdevicedriversvaryfromboardtoboard,buttheycanbecategorizedaccordingtothevonNeumannmodelapproachintroduced

5、inChapter3(seeFigure8-2).ThevonNeumannmodelcanbeusedasasoftwaremodelaswellasahardwaremodelindeterminingwhatdevicedriversarerequiredwithinaparticularplatform.Specifically,thiscanincludedriversforthemasterprocessorarchitecture-specificfunctionality,memoryandmemorymanagementdrivers,bus

6、initializationandtransactiondrivers,andI/Oinitializationandcontroldrivers(suchasfornetworking,graphics,inputdevices,storagedevices,debuggingI/O,etc.)bothattheboardandmasterCPUlevel.EmbeddedSystemBoardControlsUsageandManipulationofDataasterPMrocessor5SystemComponentsCommonlyConnect

7、edViaBusesDatafromCPorUInputDevicesStoredinMemoryuntilaCPorUOutputMemoryDeviceRequestBringsDataintotheEmbeddedSystemInputOutputSendsDataoutoftheEmbeddedSystemFigure8-2:Embeddedsystemboardorganization[8-1]BaseduponthevonNeumannarchitecturemodel(alsoreferredtoasthePrincetonarchitect

8、ure)Devicedriversaretypicallycons