A Comparative Study of the Linux A Comparative Study of the Linux and Windows Device Driver and Windows Device Driver Architectures with a focus on Architectures with a focus on

IEEE1394 (high speed serial bus) IEEE1394 (high speed serial bus) driversdrivers

Melekam TsegayeMelekam Tsegayeg98t4414@campus.ru.ac.zag98t4414@campus.ru.ac.za

Supervisors Prof. Richard Foss, Bradley Klinkradt

OverviewOverview

The Linux and Windows driver The Linux and Windows driver architecturesarchitectures

The Linux and Windows IEEE 1394 The Linux and Windows IEEE 1394 driver stacksdriver stacks

Driver development on the two platformsDriver development on the two platforms

Results of the studyResults of the study

Why the study was conducted ?Why the study was conducted ?

Microsoft Windows and Linux Microsoft Windows and Linux Two of the most popular operating systemsTwo of the most popular operating systems No previous comparisons of their driver No previous comparisons of their driver

architectures done by other researchersarchitectures done by other researchers

IEEE 1394 (firewire)IEEE 1394 (firewire) Popular bus offering high data transfer ratesPopular bus offering high data transfer rates Active research area for the CS department’s Active research area for the CS department’s

Audio Engineering GroupAudio Engineering Group

IEEE 1394IEEE 1394

Data Transfer rates of 100, 200 and 400 Data Transfer rates of 100, 200 and 400 MbpsMbps

Isochronous mode of transferIsochronous mode of transfer Guaranteed bandwidth (80%)Guaranteed bandwidth (80%)

Asynchronous mode of transferAsynchronous mode of transfer Guaranteed packet delivery (20% or more) Guaranteed packet delivery (20% or more)

Fully plug ‘n playFully plug ‘n play

IEEE 1394 Consumer ProductsIEEE 1394 Consumer Products

Device DriversDevice Drivers

A driver is a piece of software that extends a A driver is a piece of software that extends a kernel’s functionality kernel’s functionality

Drivers enable applications (through the kernel)Drivers enable applications (through the kernel) to transfer data to and from a deviceto transfer data to and from a device to control the a device to allow modification of its to control the a device to allow modification of its

attributesattributes

Composed of a set of routines that a kernel calls Composed of a set of routines that a kernel calls at appropriate times e.g. read/writeat appropriate times e.g. read/write

Typical driver routinesTypical driver routines

A driver would implementA driver would implement InitialisationInitialisation CleanupCleanup OpenOpen ReadRead WriteWrite I/O Control (ioctl)I/O Control (ioctl) CloseClose

The Windows driver architectureThe Windows driver architectureStandard model Standard model The Windows Driver The Windows Driver

Model (WDM)Model (WDM)bus, functional & bus, functional & filter driversfilter drivers

PnP & Power PnP & Power managementmanagement

CommunicationCommunication I/O request packets I/O request packets (IRPs)(IRPs)

The Linux driver architectureThe Linux driver architectureNo standard driver No standard driver model model Drivers are modulesDrivers are modules No PnP & Power No PnP & Power

management management message message dispatchingdispatching

Communication Communication through direct through direct function callsfunction calls

Side by side comparison of the two driver Side by side comparison of the two driver architecturesarchitectures

LinuxLinuxWindowsWindows

IEEE 1394 driver stacksIEEE 1394 driver stacks

The Windows IEEE 1394 stack The Windows IEEE 1394 stack closed sourceclosed source maintained by Microsoftmaintained by Microsoft stablestable

The Linux IEEE 1394 stack The Linux IEEE 1394 stack open sourceopen source maintained by the Linux 1394 community maintained by the Linux 1394 community

(private individuals)(private individuals) tagged experimentaltagged experimental

The Windows IEEE 1394 stackThe Windows IEEE 1394 stack

Host controllerHost controller

Bus driverBus driver

Client driversClient drivers

Communication Communication I/O request I/O request

block (IRB)block (IRB)

The Linux IEEE 1394 stackThe Linux IEEE 1394 stack

Host controllerHost controller

Bus driversBus drivers

Client driversClient drivers

CommunicationCommunication direct function callsdirect function calls

Direct driver Direct driver possiblepossible

Side by side comparison of the two Side by side comparison of the two

IEEE 1394 stacksIEEE 1394 stacksLinuxLinuxWindowsWindows

The Windows IEEE 1394 The Windows IEEE 1394 implementationimplementation

The Linux IEEE 1394 The Linux IEEE 1394 implementationimplementation

What operations should IEEE 1394 What operations should IEEE 1394 client drivers provide ?client drivers provide ?

Asynchronous OperationsAsynchronous Operations ReadRead WriteWrite LockLock ListenListen Register Asynchronous ListeningRegister Asynchronous Listening Deregister Asynchronous ListeningDeregister Asynchronous Listening

Isochronous operationsIsochronous operations ListenListen TalkTalk Asynchronous streamingAsynchronous streaming

What operations should IEEE 1394 What operations should IEEE 1394 client drivers provide ? (Continued)client drivers provide ? (Continued)

Bus reset handlingBus reset handling Register Bus Reset HandlerRegister Bus Reset Handler Generate Soft Bus ResetGenerate Soft Bus Reset

Obtain Bus Information (e.g. node count)Obtain Bus Information (e.g. node count)

Local configuration ROM manipulationLocal configuration ROM manipulation

Network troubleshooting Network troubleshooting Pinging of nodes Pinging of nodes

Device Driver Development Device Driver Development EnvironmentsEnvironments

Issues to be considered when Issues to be considered when creating driverscreating drivers

Memory managementMemory management The kernel provides memory allocation/de-The kernel provides memory allocation/de-

allocation routinesallocation routines Has two pools of memory (swappable, non-Has two pools of memory (swappable, non-

swappable)swappable)

Data structuresData structures The kernel provides implementations for The kernel provides implementations for

queues, lists, stacksqueues, lists, stacks Synchronisation with spin locks, mutexes, Synchronisation with spin locks, mutexes,

semaphores, signal objectssemaphores, signal objects

Issues to be considered when Issues to be considered when creating drivers (Continued)creating drivers (Continued)

Drivers routines Drivers routines must be re-entrant i.e. should be executable must be re-entrant i.e. should be executable

by multiple threads with no problemsby multiple threads with no problems avoid recursionavoid recursion

Hardware Abstraction LayerHardware Abstraction Layer use HAL routines provided by the kernel to use HAL routines provided by the kernel to

access hardwareaccess hardware

Map of software produced during Map of software produced during this studythis study

Windows raw1394 driverWindows raw1394 driver

Linux raw1394-2 driverLinux raw1394-2 driver

Linux Ieee1394diagLinux Ieee1394diag

Driver TestsDriver Tests

Tests were run to determineTests were run to determine highest data transfer rates that can be achieved by highest data transfer rates that can be achieved by

each of the IEEE 1394 driverseach of the IEEE 1394 drivers how close these came to the theoretical maximum of how close these came to the theoretical maximum of

50MB/s50MB/s

Bus analyser used to measure Bus analyser used to measure the duration of data transfers the duration of data transfers the amount of data transferredthe amount of data transferred

Calculated Calculated the data transfer rate in MB/sthe data transfer rate in MB/s

Test resultsTest results

Isochronous mode Isochronous mode Windows raw1394Windows raw1394

8.9 MB/s 8.9 MB/s packet size 1024 bytespacket size 1024 bytes

Linux raw1394Linux raw13944.5 MB/s 4.5 MB/s packet size 512 bytespacket size 512 bytes

Isochronous mode (buffered)Isochronous mode (buffered) Linux raw1394-2Linux raw1394-2

8.9 MB/s 8.9 MB/s packet size 1024 bytespacket size 1024 bytes

Windows raw1394Windows raw139417.7 MB/s17.7 MB/spacket size 2048 bytespacket size 2048 bytes

Test results (continued)Test results (continued)

Drivers from both Linux and Windows do Drivers from both Linux and Windows do not transfer data at a rate close to the not transfer data at a rate close to the theoretical theoretical 50MB/s50MB/s They achieve almost half that They achieve almost half that

due to the PCI bus bottleneck (theoretical due to the PCI bus bottleneck (theoretical 132MB/s) 132MB/s)

In practice have that availableIn practice have that available shared by all I/O devices attached to the PCI busshared by all I/O devices attached to the PCI bus The PCI bus has latency problemsThe PCI bus has latency problems

driver implementation may not be efficientdriver implementation may not be efficient

ConclusionConclusion

A comparison of the Windows and Linux driver A comparison of the Windows and Linux driver architectures has shown thatarchitectures has shown that Drivers for the two platform have similar componentsDrivers for the two platform have similar components

composed of routines for performingcomposed of routines for performing I/O and device controlI/O and device control

drivers are modules which are loadable at runtimedrivers are modules which are loadable at runtime Windows has a formally defined driver model, Linux Windows has a formally defined driver model, Linux

does not.does not. PnP and power management support integrated in PnP and power management support integrated in

the Windows architecture, not so in Linuxthe Windows architecture, not so in Linux

Conclusion (continued)Conclusion (continued)

A comparison of the Windows and Linux IEEE A comparison of the Windows and Linux IEEE 1394 stacks has shown that1394 stacks has shown that Their IEEE 1394 driver stacks are broken up into Their IEEE 1394 driver stacks are broken up into

similar layerssimilar layers host controller, bus and client driver layershost controller, bus and client driver layers

Each stack provides the standard IEEE 1394 Each stack provides the standard IEEE 1394 operations (both asynchronous and isochronous)operations (both asynchronous and isochronous)

The Linux IEEE 1394 stack is open source while The Linux IEEE 1394 stack is open source while the Windows stack is proprietarythe Windows stack is proprietary Easier to create IEEE 1394 drivers for Linux than Easier to create IEEE 1394 drivers for Linux than

Windows since all source code is availableWindows since all source code is available

Future workFuture work

IEEE 1394.1 bridge awarenessIEEE 1394.1 bridge awarenessIEEE 1394.1 IEEE 1394.1

allows extending the no. of nodes to 64K instead of the current 63allows extending the no. of nodes to 64K instead of the current 63 still in draft phasestill in draft phase

The Windows and Linux IEEE 1394 driver developers did not take The Windows and Linux IEEE 1394 driver developers did not take into account IEEE1394.1 bridging in their designinto account IEEE1394.1 bridging in their designThis study identified bridge awareness requirementsThis study identified bridge awareness requirements

implementation possible for the Linux 1394 stackimplementation possible for the Linux 1394 stack not for the Windows 1394 stack (closed source)not for the Windows 1394 stack (closed source)

Full IEEE 1394.1 implementation and testing not done during this Full IEEE 1394.1 implementation and testing not done during this studystudy

no IEEE 1394.1 bridging hardware availableno IEEE 1394.1 bridging hardware available the standard may changethe standard may change

Questions ?Questions ?