LinuxPlatformDrivers:UnderstandingandImplementing

Introduction

Forembeddedsystems,it’scrucialtohaveadriverthatcommunicateswiththeplatform.Insteadofdesigninganewdriverfromscratch,theLinuxplatformdriverframeworkoffersastandardinterfaceforcommunicationwiththehardware.Inthisarticle,wewilldiscussplatformdrivers,theiradvantages,andhowtoimplementthem.

WhatarePlatformDrivers?

PlatformdevicesarethedevicesthatareknowntoLinuxatruntime.Thedriversthatcontrolthesedevicesareknownasplatformdrivers.Theyaredifferentfromtheregulardriversthataremodule-basedandloadedon-demand.Platformdriversinitializedevicesduringboot-upandmakethemavailabletothesystemforuse.

AdvantagesofusingPlatformDrivers

Platformdrivershavemanyadvantagesoverregulardrivers,including:

• Standardinterface:Platformdriverframeworkprovidesastandardinterfaceforcommunicationwiththehardware,soitisportableacrossdifferentplatforms.
• AcceleratedDevelopment:Platformdrivershelptosavedevelopmenttimebyprovidingapre-madeframeworkfordevelopingcustomdrivers.
• OptimalPerformance:Theplatformdriverframeworkusesdirectmemoryaccess(DMA)totransferdatabetweenthedeviceandthesystemmemory.ThishelpstoreducetheloadontheCPUandimprovetheoverallperformance.

ImplementingaPlatformDriver

Thekeystepsinvolvedinimplementingaplatformdriverareasfollows:

1.DeviceTreeRegistration

DevicetreeregistrationisdonetopresentthedeviceinformationtotheLinuxkernel.Thedevicetreemustspecifythedevice’scharacteristics,includingthedevicename,interruptnumber,andmemorymap.

2.WritingaDriverProbeFunction

Afterdevicetreeregistration,theLinuxkernelwillcallthedriver’sprobefunction.Inthisfunction,thedrivershouldinitializethedeviceusingtheinformationprovidedinthedevicetree.Inaddition,thedrivershouldregisterthedevicewiththeDeviceModelinterfaceoftheLinuxkernel.

3.WritingaDriverRemoveFunction

Theplatformdriverframeworkcallsthedriver’sremovefunctionwhenthedeviceisunregistered.Inthisfunction,thedrivershouldreleasetheresourcesacquiredintheprobefunction,suchasmemoryandinterrupts.

Conclusion

Platformdriversofferastandardframeworktointeractwiththehardware,thusreducingthedevelopmenttime.DMAcapabilitiesofplatformdriversresultinoptimalperformance.Byimplementingthethreekeystepsmentioned,onecaneasilywriteplatformdriversforthedevices.