Logical Device Drivers Collection Symbian OS Architecture

Logical Device Drivers Collection

Thu, 24 Mar 2011 07:44:32 | Symbian OS Architecture

Logical (see Figure 11.9) device drivers (LDDs) are plug-ins to the kernel device-driver framework that provide the logical abstraction of hardware

Kernel Services	Logical Device Drivers

ASSP	Variant	Kernel Architecture

Figure 11.7 Kernel Architecture collections

: Kernel Services

Logical Device Drivers

Ether.

USB

Other

Media

Audio

Speech Driver

Video

MIDI

SD Card Driver

Periph.

Bus Cntrllrs.

Driver

LDDs

Drivers

Driver

Figure 11.9

Table 11.4 Logical Device Drivers
Component Name	Development Name
Ethernet Driver	ETHERDRV
USB Driver	USBC
Audio Driver	SOUNDDEV
MIDI Driver	DEVMIDI
Speech Driver	DEVASR
Video Driver	DEVVIDEO
Other LDDs
Media Drivers	MEDUSII, MEDUSII_CRASHLOG, MEDUSIIS
SD Card Driver	SDCARD4C
Peripheral Bus Controllers	EPBUS

devices, and accept the physical device driver (PDD) plug-ins, which communicate with real hardware.

Symbian OS supplies specific Ethernet and USB drivers, as well as hardware 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 for Ethernet cards, including the emulator.

• The USB Driver is a logical device driver for USB. The standard USB software architecture on Symbian OS supports dynamically configurable USB 2.0 device functionality.

• The Audio, MIDI, Speech and Video accelerator API plug-ins to the Multimedia Device Framework (MDF), the lowest-level framework supporting multimedia services, are used by MDF controllers. They all include hardware- or kernel-dependent components.

◦ DevVideo is the hardware-abstraction layer for video decoding and encoding acceleration enabling playing and recording of video; 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 MIDI engines.

◦ DevSound is the hardware-abstraction layer for digital audio acceleration enabling Playing, Recording, Conversion and Tone generation of sounds; it includes a client API that enables policy management (e.g. request contention and file-type matching).

◦ DevASR is the hardware-acceleration API for Automatic Speech Recognition, allowing the computationally intensive speech-recognition algorithms to be performed in hardware, where present.

• The peripheral bus controllers for supported variants are implemented as kernel-side DLLs that interface media and I/O device drivers to PC-card or MMC-card socket hardware.

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