Msc Present

8/2/2019 Msc Present

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A Comparative Study of the Linux

and Windows Device DriverArchitectures with a focus on

IEEE1394 (high speed serial bus)

drivers

Melekam [email protected]

Supervisors Prof. Richard Foss, Bradley Klinkradt


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Overview

The Linux and Windows driverarchitectures

The Linux and Windows IEEE 1394

driver stacksDriver development on the two platforms

Results of the study


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Why the study was conducted ?

Microsoft Windows and Linux

Two of the most popular operating systems

No previous comparisons of their driverarchitectures done by other researchers

IEEE 1394 (firewire)

Popular bus offering high data transfer rates

Active research area for the CS departments

Audio Engineering Group


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IEEE 1394

Data Transfer rates of 100, 200 and 400Mbps

Isochronous mode of transfer

Guaranteed bandwidth (80%)

Asynchronous mode of transfer

Guaranteed packet delivery (20% or more)

Fully plug n play


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IEEE 1394 Consumer Products


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Device Drivers

A driver is a piece of software that extends akernels functionality

Drivers enable applications (through the kernel)

to transfer data to and from a device

to control the a device to allow modification of itsattributes

Composed of a set of routines that a kernel callsat appropriate times e.g. read/write


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Typical driver routines

A driver would implement

Initialisation

Cleanup

Open

Read

Write

I/O Control (ioctl)

Close


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The Windows driver architecture

Standard model The Windows

Driver Model

(WDM)bus, functional &filter drivers

PnP & Power

management Communication

I/O request packets(IRPs)


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The Linux driver architecture

No standard drivermodel

Drivers aremodules

No PnP & Powermanagementmessage

dispatching Communication

through directfunction calls


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Side by side comparison of the two driverarchitectures

LinuxWindows


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IEEE 1394 driver stacks

The Windows IEEE 1394 stack closed source

maintained by Microsoft

stable

The Linux IEEE 1394 stack open source

maintained by the Linux 1394 community(private individuals)

tagged experimental


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The Windows IEEE 1394 stack

Host controller

Bus driver

Client driversCommunication

I/O request

block (IRB)


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The Linux IEEE 1394 stack

Host controller

Bus drivers

Client driversCommunication

direct function calls

Direct driver

possible


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Side by side comparison of the twoIEEE 1394 stacks

LinuxWindows


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The Windows IEEE 1394implementation


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The Linux IEEE 1394implementation


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What operations should IEEE 1394client drivers provide ?

Asynchronous Operations Read Write Lock Listen Register Asynchronous Listening Deregister Asynchronous Listening

Isochronous operations Listen Talk Asynchronous streaming


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

Bus reset handling

Register Bus Reset Handler

Generate Soft Bus Reset

Obtain Bus Information (e.g. node count)

Local configuration ROM manipulation

Network troubleshooting Pinging of nodes


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Device Driver DevelopmentEnvironments


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Issues to be considered whencreating drivers

Memory management The kernel provides memory allocation/de-

allocation routines

Has two pools of memory (swappable, non-swappable)

Data structures The kernel provides implementations for

queues, lists, stacks

Synchronisation with spin locks, mutexes,semaphores, signal objects


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Map of software produced during

this study


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Windows raw1394 driver


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Linux raw1394-2 driver


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Linux Ieee1394diag


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Driver Tests

Tests were run to determine

highest data transfer rates that can be achieved byeach of the IEEE 1394 drivers

how close these came to the theoretical maximum of50MB/s

Bus analyser used to measure

the duration of data transfers

the amount of data transferred

Calculated

the data transfer rate in MB/s


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Test results

Isochronous mode Windows raw1394

8.9 MB/spacket size 1024 bytes

Linux raw1394


Isochronous mode (buffered) Linux raw1394-2


Windows raw139417.7 MB/spacket size 2048 bytes


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Test results (continued)

Drivers from both Linux and Windows donot transfer data at a rate close to thetheoretical

50MB/s They achieve almost half that

due to the PCI bus bottleneck (theoretical132MB/s)

In practice have that available shared by all I/O devices attached to the PCI bus

The PCI bus has latency problems

driver implementation may not be efficient


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Conclusion

A comparison of the Windows and Linux driverarchitectures has shown that

Drivers for the two platform have similar components

composed of routines for performing I/O and device control

drivers are modules which are loadable at runtime

Windows has a formally defined driver model, Linuxdoes not.

PnP and power management support integrated inthe Windows architecture, not so in Linux


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Conclusion (continued)

A comparison of the Windows and Linux IEEE1394 stacks has shown that Their IEEE 1394 driver stacks are broken up into

similar layers

host controller, bus and client driver layers

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

The Linux IEEE 1394 stack is open source while

the Windows stack is proprietary Easier to create IEEE 1394 drivers for Linux than

Windows since all source code is available


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Future work

IEEE 1394.1 bridge awarenessIEEE 1394.1 allows extending the no. of nodes to 64K instead of the current 63 still in draft phase

The Windows and Linux IEEE 1394 driver developers did not take

into account IEEE1394.1 bridging in their designThis study identified bridge awareness requirements implementation possible for the Linux 1394 stack not for the Windows 1394 stack (closed source)

Full IEEE 1394.1 implementation and testing not done during thisstudy

no IEEE 1394.1 bridging hardware available the standard may change


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Questions ?

Documents

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