The Symbian OS (779886), страница 64
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Thehardware reference platform for Symbian OS v8 releases was the IntelLubbock development board. For Symbian OS v9, the hardware referenceplatform is based on the Texas Instruments OMAP development boards.For Symbian OS v9.0 and v9.1, the hardware reference platform is theH2 development board with OMAP 1623 (ARMV5-based core):• other versions of the H2 boards are not officially supported• includes a DSP, SD/MMC/SDIO card, USB, camera, display(240×320, rotatable, 8 or 16 bits per pixel), NAND flash• operating system installation from MMC or serial loads either intoRAM or into NOR Flash on the board• JTAG (IEEE 1149.1) is also supported.From Symbian OS v9.2, the hardware reference platform is the H4development board with OMAP 2420 (ARMv6-based core):KERNEL ARCHITECTURE COMPONENT COLLECTIONS295• adds USB for bootable image source to H2• introduces some NAND-flash differences compared to the H2 board.11.8 Kernel Architecture Component CollectionsThe Kernel Architecture block in the system model contains four separatecollections (see Figure 11.7): Kernel Services, Logical Device Drivers,ASSP, and Variant.Kernel Services CollectionThe EKA2 component consists of the nanokernel, which is the realtime kernel core, and the operating system kernel that builds the basicthreading, process and memory models on top of it.Table 11.3 Kernel Services ComponentsComponent NameDevelopment NameKernel Architecture 2E32 EKA2Logical Device Drivers CollectionLogical (see Figure 11.9) device drivers (LDDs) are plug-ins to the kerneldevice-driver framework that provide the logical abstraction of hardwareKernelServicesASSPLogical Device DriversVariantFigure 11.7 Kernel Architecture collectionsKernelServicesEKA2KernelFigure 11.8 Kernel Services componentsKernelArchitecture296THE KERNEL SERVICES AND HARDWARE INTERFACE LAYERLogical Device DriversEther.DriverUSBDriverOtherLDDsMediaDriversAudioDriverSpeechDriverVideoDriverMIDIDriverSDCardDriverPeriph.BusCntrllrs.Figure 11.9Table 11.4 Logical Device DriversComponent NameDevelopment NameEthernet DriverETHERDRVUSB DriverUSBCAudio DriverSOUNDDEVMIDI DriverDEVMIDISpeech DriverDEVASRVideo DriverDEVVIDEOOther LDDsMedia DriversMEDUSII, MEDUSII CRASHLOG,MEDUSIISSD Card DriverSDCARD4CPeripheral Bus ControllersEPBUSdevices, and accept the physical device driver (PDD) plug-ins, whichcommunicate with real hardware.Symbian OS supplies specific Ethernet and USB drivers, as well ashardware accelerator plug-ins used by the Media Device Framework,which form part of the hardware abstraction for multimedia devices.• The Ethernet Driver is a logical device-driver implementation forEthernet cards, including the emulator.• The USB Driver is a logical device driver for USB.
The standardUSB software architecture on Symbian OS supports dynamicallyconfigurable USB 2.0 device functionality.• The Audio, MIDI, Speech and Video accelerator API plug-ins to theMultimedia Device Framework (MDF), the lowest-level frameworksupporting multimedia services, are used by MDF controllers. Theyall include hardware- or kernel-dependent components.KERNEL ARCHITECTURE COMPONENT COLLECTIONS297◦ DevVideo is the hardware-abstraction layer for video decodingand encoding acceleration enabling playing and recording ofvideo; it includes a client API that enables policy management(e.g.
request contention and file-type matching).◦ DevMIDI is the API that supports hardware-accelerated MIDIengines.◦ DevSound is the hardware-abstraction layer for digital audioacceleration enabling Playing, Recording, Conversion and Tonegeneration of sounds; it includes a client API that enables policymanagement (e.g. request contention and file-type matching).◦ DevASR is the hardware-acceleration API for Automatic SpeechRecognition, allowing the computationally intensive speechrecognition algorithms to be performed in hardware, wherepresent.• The peripheral bus controllers for supported variants are implementedas kernel-side DLLs that interface media and I/O device drivers toPC-card or MMC-card socket hardware.ASSP CollectionHardware dependencies divide between ASSP dependencies, based onproperties of the CPU core and the peripherals packaged with it in thesame silicon chip, and additional ‘off-chip’ hardware peripherals.Table 11.5 ASSP ComponentsComponent NameDevelopment NameASSPOMAP 1623Isolating the ASSP-dependent code allows it to be reused on multiplesystems that use the same ASSP.
OMAP 1623 is the ASSP supported inthe Symbian OS v9 hardware reference platform, as used in the TexasInstruments H2 development board. (Other H2 ASSPs are not supported.)The ASSP module contains source code tailored to a range of differentmicroprocessors (e.g. ARM720/920/SA1100/Xscale). See Figures 11.9 and11.10.ASSPOMAP2420Figure 11.10 ASSP components298THE KERNEL SERVICES AND HARDWARE INTERFACE LAYERVariantBootstrapOMAPH4HRPVariantOMAPH2VariantLubbckVariantEmulatorPDDsBoardSupportPckgsFlashTranslationLayerFigure 11.11 Variant componentsTable 11.6 Variant ComponentsComponent NameDevelopment NameBootstrapBOOTSTRAPEmulatorWINS VARIANT EKA2Lubbock VariantLUBBOCK EKA2OMAP H2OMAP H2OMAP H4OMAPH4HRPPDDsBoard Support PackagesFlash Translation LayerUNISTORE2 DRIVERSVariant CollectionThe Variant collection contains components which are associated withoff-chip hardware, that is, which are independent of the ASSP.• The Bootstrap component prepares hardware including memory andperipherals, maps virtual address space if an MMU is present, and startsthe kernel.
It includes processor-, MMU- and other device-dependentcode, as well as a generic layer.• The emulator component is treated as a hardware target variant. TheEmulator runs on Microsoft Windows platforms and maps SymbianOS services and logical devices to Microsoft Windows APIs and localhardware. Single-process implementation uses Microsoft Windowsthreads to emulate Symbian OS processes. It is valuable for highlevel programming, but the implementation creates practical issues forlow-level and device-dependent programming compared to hardwaretargets.• The Lubbock Variant component is Variant code for the Symbian OSv8 hardware reference platform.KERNEL ARCHITECTURE COMPONENT COLLECTIONS299• The OMAP H2 component is Variant code for the Symbian OS v9.1hardware reference platform. (From Symbian OS v9.2 the referencehardware platform moves up to the OMAP H4 board.)• The PDDs are physical device drivers, low-level plug-ins used byLDDs providing the device-dependent level of the two-tier devicedriver model.• The kernel requires additional loading and media translation support when running on NAND-flash devices.
A special boot loaderis required to move the kernel into RAM so that it can execute(since NAND flash is not byte-addressable), together with a translation layer that manages the flash device and presents a standardbyte-readable and -writable interface to the file system. The FlashTranslation Layer component is the original file system plug-in implementation of flash-driver support. Media drivers provide a newerimplementation (implemented as conventional Symbian OS devicedrivers), supporting more NAND formats: small, large and OneNAND.12The Java ME Subsystem12.1 IntroductionSymbian OS offers licensees an optional Java implementation.
SinceSymbian OS v7.0, this has been based on the Java 2 Platform, MicroEdition (Java ME) MIDP and CLDC specifications, which have becomethe standard for Java on mobile phones and other communicator-styledevices.Java ME is subdivided into configurations, profiles and optional packages. A Java ME configuration provides a basic1 Java platform for a largeclass of constrained devices by defining a Java Runtime Execution (JRE)environment consisting of a Java language subset, a Java Virtual Machine(JVM) and a base set of necessary class libraries.
It is commonly based ona subset of the J2SE APIs.Currently, there are two Java ME configurations:• Connected Limited Device Configuration (CLDC)• Connected Device Configuration (CDC).A Java ME profile sits on top of a configuration to complete the JREby adding more high-level APIs, thereby preparing a device for a specificdevice category. Currently, there are two common Java ME profiles:• Mobile Information Device Profile 1.0 (MIDP1)• Mobile Information Device Profile 2.0 (MIDP2).1See the CLDC specification at http://jcp.org/aboutJava/communityprocess/final/jsr139.302THE JAVA ME SUBSYSTEMOptional packages add functionality to the Java ME platform by offeringstandard APIs for various technologies such as advanced multimedia, 3Dgraphics, file system access, web services and much more.A widely adopted standard is the combination of MIDP and CLDCto provide a complete Java platform for mobile phones and similardevices.
MIDP applications are known as MIDlets. With MIDP 2.0the specification becomes rich enough to support a wide variety ofsophisticated applications.12.2Requirements of the Java ME SubsystemJava is an important application environment for mobile phones, supporting a multiplatform third-party market for downloadable and installableprograms (including games, utilities and media players), a standard environment for enterprise developers seeking to extend information systemsto mobile phone users within organizations and a standard platform formobile phone services, as well as a branding and personalization mechanism (through custom applications) for network operators and others inthe phone retail chain.Platform independence is an important part of Java’s philosophy thatapplies as much to the MIDP context as to desktop Java implementations.The Symbian OS implementation of Java ME provides a standard environment for installing and running MIDlets, with access to the underlyingoperating system services through the supported MIDP 2.0 APIs, whichinclude a number of optional APIs – for example, Mobile Media, 3DGraphics and File GCF – as well as the Java Technology for the WirelessIndustry (JTWI) standard, which aims to standardize MIDP support formobile phones, and the Unified Emulator Interface (UEI), a developmenttools standardization initiative.12.3Design Goals for the Java ME SubsystemSymbian OS provides a rich and powerful host for the Java ME implementation, but also poses some great challenges.
These are a result of thearchitectural differences between Symbian OS and the Java platform andthe differences between Symbian OS components and the MIDP APIswhich are built on top of the Symbian APIs.• There are some specific mismatches between Symbian OS and Javamodels; in particular their threading models are incompatible.• Symbian OS has its own native application model (for C++ applications), with which the MIDP lifecycle must be integrated if MIDletsare to have a seamless, native application lifecycle.EVOLUTION OF JAVA ON SYMBIAN OS303• Symbian OS has a rich set of native controls, localization abstractions,custom dialogs, input mechanisms, and so on, all of which areexpected to be customized for look and feel by the providers of thevariant user interface with which the operating system is integratedon any particular Symbian OS device.
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