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epics-ioc

HardwareLinksandDriverSupport

COLLABORATORS

TITLE:

HardwareLinksandDriverSupport

ACTIONNA不知深浅po1v2笔趣阁 MEDATESIGNATUREWRITTENBYMichaelDavidsaverSeptember2009

REVISIONHISTORY

NUMBERDATEDESCRIPTIONNAME

Contents

1Introduction1

2LinkingRecordsTogether13LinkingRecordsToHardware14WhenaHardwareLinkisNotEnough25DeviceSupport

PrivateData26DriverSupportandtheVirtualDevice37TheFullCrate38Example139Example2410Example35

11Example4(Full)5

11.1GlobalDe?nitions(5)

11.2DBD(6)

11.3IOCShellFunctions(6)

11.4DeviceSupport(8)

11.5DriverSupport(Uniform)(8)

11.6DriverSupport(Gaussian)(9)

ListofFigures

1AnExampleProcessDatabase(1)

ListofTables

1HardwareLinkTypes(2)

1Introduction

InanEPICScontrolsystemtheInputOutputController(IOC)isthenamegiventothepieceofsoftwarewhichsitsbetweenthe

netgercontrolsystemseesitasasetof

theIOCaChannelisrevealedtobeana?eldofaRecordintheProcess

Database,aProcessVariable(PV).lowsinformationto?

owbetweenRecordsswhentheyareprocessed.

ThisisthemilehighviewofanIOCandlacksseveralofthekeydetailswhichenableonetotakeanewpieceofhardware

ollowingdiscussionwewillstartattheProcessDatabaseandmovetowardsthe

mstobediscussedinclude:linkingtohardware,howtorepresentcomplexdevices,andtheFullCrate.

Figure1:AnExampleProcessDatabase

Inthedatabasepicturedabovethereare?ourPVsarelinkedtotwo

?fthPVmightbeofarecordtypewhichdoesnotneeddevicesupport,orwhichusessoft

devicesupport.

2LinkingRecordsTogether

‘kinds’arethosewhichlinktogethertworecords,and

eeclassesare:Input,Output,relinksareeitherInputor

Outputlinks.

Moreattentionisgiventothe?rstkindbecause

isthesecondhowever,whichwewillfocuson.

InFigure1anexampleoflinkingtworecordstogethercanbeseenbetweenthePVsA:1andA:uldbeaninputlink

byA:2topullthevalueofA:1,itcouldbeanoutputlinkbyA:1topushavalueintoA:2,oritcouldbeaforwardlinkbyA:1to

A:2.3LinkingRecordsToHardware

Hardwarelinksservetoassociatearecord’sdevicesupportwithaparticular(virtual)?gureabovePVA:2hasan

hardwareoutputlink,andA:3hasahardwareinputlink.

Unlikealinkbetweentworecords,endsonwhichphysicalmachineandIOC

venmeaningbythedevicesupport,sothesamehardwarelinkstringwillmeantwodifferentthings

whenusedwithtwodifferentdevicesupportsinthesameIOC.

TypeFieldformat

VME_IO‘#CxxSyy@zzz’

CAMAC_IO‘#BxxCyyNzzAttFuu@vvv’

AB_IO‘#LxxAyyCzzStt@uuu’

GPIB_IO‘#LxxAyy@zzz’

BITBUS_IO‘#LxxNyyPzzStt@uuu’

INST_IO‘@xxx’

BBGPIB_IO‘#LxxByyGzz@ttt’

RF_IO‘#RxxMyyDzzEtt’

VXI_IO‘#VxxCyySzz@ttt’

Table1:HardwareLinkTypes

The9allowedhardwarelinktypesarelistedintableTable1.

yareimplimented,andhowtheyareintendedtobeused.

AHWlinktypenameisjustalabelappliedtoonearmofaCunion(de?nedinlink.h).Forexample,aVME_IOlinkmightbe

written“#C0x4000S0x8@signed”.Thisisparsedandplacedintheappropriatearmoftheunion;whichisitselfaCstructure

withthreemembers:card,signal,?arsingno

allthatahardwarelinkis.

Thiscollectionocethereissomuch

variationinthewaydiffererentscheme

isatradeofftoremovesomeparsing(ieatoi())anderrorcheckingcodewhichwouldotherwisebereplicatedbyeverydevice

support,andmoveitintotheprocessdatabaseframework.

AlinktypelikeVME_IOissonamedbecauseitisoftenconvienenttothinkofaddressingavmecardbyslotnumberanda

function/channelcode,dsdonotneedtouseVME_IO

typelinksandGPI

BdevicesdonotneedtouseGPIB_ME_IOandGPIB_IOlinksstorethesamedata(twoshortintsanda

string)fferonlyinthenamesusedinthetwoarmsofthe

Cunion.

4WhenaHardwareLinkisNotEnough

Heaksdownwhentheinformationtobe

passedbe秋思翻译 comeslargeorwhenthereisinitializationtobeperformed.

Itisdif?culttohandleinitializationtasks,whichmusthappenonceandonlyonce,inahardwarelinkwhichisduplicatedin

mptingtothinkofgivingonerecorda‘special’linkwhichtellsdevicesupportwhentoinitialize,butthereis

reinitializationcanbedoneeasilyandcleanlyintheIOCShell.

AcommonpatternisforaDeviceSupporttoprovideanIOCShellfunctiontoacceptandpreprocesscomplexhardwaread-

forsupporthardwarelinks

passtheintegerkeytotheDeviceSupportforeachRecord,whichmustindividuallypreformalookuptoretrievethecomplete

okupisusuallydonetheDeviceSupportinit_pleofthisisgivenbelow

inSection9.

5DeviceSupportPrivateData

Theuseofhardwarelinksimpliessomesortoflookuptogetfromasetofshortintegersandastringtoapointertoamemory

mappeddevice,orasystem?ledescriptor/socketformessagebaseddevices.

Itwouldbeinef?sreasonthedevicesupportauthoris

providedwiththeDeviceSupportPrivate(dpvt)?eld,?eldisavoid*whichmaybeused

otbeaccessviaChannelAccess.

Itcouldbeusedtostorethe

commonlyitwillstoreapointertoastructurede?nedbythedevicesupportauthor.

6DriverSupportandtheVirtualDevice

EPICSDriverSupportisnotawellde?dbeanyofthefollowingamongothers:

Asetoffunctionssharedbetweenseveraldevicesupports.

InvolveIOCShellfunctionsforsetup.

AninterfacetoanOperatingSystemdriver.

The“of?cial”de?nitionofDriverSupportisintermsofthedrvetstructurede?ableoffunctionpointers

similartotheDeviceSupportdsettable.

Itprovidesawaytode?uldbeusedtoabstractawaythedifferences

betweenvarientsofacardorevenbusaccessmethod().Theabstractoperationspresentedbythisinterfaceto

DeviceSupportareessentuallya‘VirtualDevice’.

casestheextraabstractionitprovidesserveonlytoaddcomplexitywithnorealbeni?t.

Knowingwhentouseitisaskillwhichdevelopswithtime.

TheexampleSection11belowextendsthePRNGdevicesupportdevelopedintheBasicEPICSDeviceSuppo锈组词 rtdocument

todemonstrateacasewhereDriverSupportcanbeuseful.

7TheFullCrate

EPICSisadistributedcontrolsystemandmustbeabletoscalewell,bothinnumberofIOCsaswellasthesizeofanyoneof

theseIOCS.

TheconceptsofLinkingexiststoenforceisolationbetweenrecords(andassociatedDeviceSupports).Theideaisthatif

recordsinstancescanonlyinteractinwellunderstoodwaysthenitiseasiertoscaletoanarbitrarilylargenumberof

relinkingallowsthisisolationtobebrokentotheextentnecessarytodealtherealitywithcomplexdevices.

mple,?rstthatanADCcardhasachannel,then

thatithasmanychannels,and?portanttoconsiderthataDevice

SupportwillgointoanIOCwhichmanyhavemanyofitsdevices,andotherdeviceswhichitshouldnotinterferewith.

Conlresourcesbeallocated?What

baseaddressshouldeachcardbeassigned?Willall20cardsinterrupttheCPU(atthesametime)?Thesearethetypesof

questionswhichmustbeansweredtocreateanIOCwhichcanscale.

8Example1

ConsiderthefollowingaconcreteexampleoftheA:*PVsinthedatabaseillistratedin?gureFigure1.

Thehardwarespeci?cdevicesupportisde?nedinadatabasede?nition.

device(ao,GPIB_IO,devAoMine,\"MyDevice\")

device(ai,GPIB_IO,devAiMine,\"MyDevice\")

gavalueto0x04causesthevalueof0x08to

fthetypeGPIB_IOareusedtofurtherillustratethatthesenamesmeannothing.

ThedevicesupportdevAoMinetakesthesumofthetwointegerpartsofthehardwarelinkandusesthisastheVMEaddress

mstringisusedtoholdoptionalmodi?ers.

TherecordA:1existstoprovideaseperatelinearscalingforthesetting.

TheforwardlinkbetweenA:2andA:3causesthe0x8registertobereadafterthe0x4registeriswritten.

record(ao,\"A:1\"){

field(DTYP,\"SoftChannel\")

field(OUT,\"A:2\")

field(PINI,\"Yes\")

field(UDF,0)

field(VAL,4.2)

field(CONV,\"Linear\")

field(ESLO,-2.0)

field(EOFF,1.0)

field(EGU,\"mm\")

field(FLNK,\"A:2\")

}

record(ao,\"A:2\"){

field(DTYP,\"MyDevice\")

field(OUT,\"#L0x4000A0x04@signed\")

field(FLNK,\"A:3\")

}

record(ai,\"A:3\"){

field(DTYP,\"MyDevice\")

field(OUT,\"#L0x4000A0x08@signed\")

}

9Example2

icesupportwritermakesthedecisiontocreateanIOCShell

functioncalledinitMyDev(int,int,string)andaddsittotheIOCstartscript.

dbLoadDatabase(\"dbd/\")

mydevioc_registerRecordDeviceDriver(pdbase)

initMyDev(0,0x4000,\"signed\")

dbLoadRecords(\"db/\",\"prefix=A:,card=0\")

iocInit()

ThisassociatestheVMEcardwiththeA16baseaddress0x4000withtheintegerkey0,whichispassedas$(card)whenthe

recordsareloaded.

Thedatabasethenbecomesthefollowing:

record(ao,\"$(prefix)1\"){

field(DTYP,\"SoftChannel\")

field(OUT,\"A:2\")

field(PINI,\"Yes\")

field(UDF,0)

field(VAL,4.2)

field(CONV,\"Linear\")

field(ESLO,-2.0)

field(EOFF,1.0)

field(EGU,\"mm\")

field(FLNK,\"A:2\")

}

record(ao,\"$(prefix)2\"){

field(DTYP,\"MyDevice\")

field(OUT,\"#L$(card)A0x04@\")

field(FLNK,\"A:3\")

}

record(ai,\"$(prefix)3\"){

field(DTYP,\"MyDevice\")

field(OUT,\"#L$(card)A0x08@\")

}

Itthissimpleexamplewedonotgainmuchforthetrouble,butthisapproachis?exibleinawaythathardwarelinksaloneare

not.

10Example3

ychangerequiredisintheIOCstartscript.

dbLoadDatabase(春望写作背景 \"dbd/\")

mydevioc_registerRecordDeviceDriver(pdbase)

initMyDev(0,0x4000,\"signed\")

i贫贱夫妻百事哀上下联 nitMyDev(1,0x5000,\"signed\")

initMyDev(2,0x6000,\"signed\")

initMyDev(3,0x7000,\"signed\")

initMyDev(4,0x8000,\"signed\")

dbLoadRecords(\"db/\",\"prefix=A:,card=0\")

dbLoadRecords(\"db/\",\"prefix=B:,card=1\")

dbLoadRecords(\"db/\",\"prefix=C:,card=2\")

dbLoadRecords(\"db/\",\"prefix=D:,card=3\")

dbLoadRecords(\"db/\",\"prefix=E:,card=4\")

iocInit()

Thiswillcreate?vecopiesofthePVsde?nedindb/,eachwithadifferentpre?xcommunicatingwithadifferentcard.

Thefactthatthiscanbedonewithoutmodifying(orevenrecompiling)anyoftheDeviceSupportcodeiswhatallowsan

EPICSIOCtoquicklyandeasilyscaletolargenumbersofdevices.

11Example4(Full)

icesupportforthepseudo-randomnumbergenerator

developedintheBasicversinthis

casewillbeusedtoselectbetweentwopossiblerandomnumberdistributions.

11.1GlobalDe?nitions

Webeginbyde?the‘VirtualDevice’casewe

haveonlytwooperations:ateoperationreferstocreatinga‘VirtualDevice’,andcouldalsobenamed

nd.

The‘hardwareaddress’d*returnedbythe

createfunctionmustbeusedwhenthereadfunctioniscalled,interis

effectivelythethispointerofC++.

Thefollowingcodeshouldbeplacedinthe?leprngApp/src/drvprngdist.h.

typedefvoid*(*create_prng_fun)(unsignedintseed);

typedefint(*read_prng_fun)(void*tok);

structdrvPrngDist{

drvetbase;

create_prng_funcreate_prng;

read_prng_funread_prng;

};

Thisde?nitionmustbesharedbetweentheDriverSupportcodeandtheDeviceSupport(s)whichwilluseit.

Nowwede?neanadditionalstructurewhichcanbethoughofasthepublicdatamembersofthedrvPrngDistclass.

structinstancePrng{

ELLNODEnode;/*mustbefirst*/

structdrvPrngDist*table;

void*token;

intid;

};

AELLNODEisalsoincludedasaconvinienceforthelookupPrngfunction;whichwillbeusedbyDeviceSupporttolocatea

speci?cinstanceofdrvPrngDistbasedontheidnumberpassedtoitinahardwarelink.

structinstancePrng*lookupPrng(shortN);

11.2DBD

Atthispointweshouldcreatethedatabasede?nitionasprngApp/src/.

device(ai,VME_IO,devAiPrngDist,\"RandomDistribution\")

driver(drvPrngUniform)

driver(drvPrngGaussian)

registrar(prngDist)

11.3IOCShellFunctions

CreatinginstanceofPRNG‘VirtualDevices’willbeaccomplishedwithanIOCShellfunctioncalledcreatePrnginthe?le

staticELLLISTdevices={{NULL,NULL},0};

staticconstchardpref[]=\"drv凤求凰司马相如 Prng\";

Herewede?nealistwhichwillholdallcreateddeviceinstancesandthepre?xforDriverSupportnames(asseeninthe

dbd).void

createPrng(intid,intseed,constchar*dist)

{

unsignedints=(unsignedint)seed;

char*dname=NULL;

size_范晔的作品 tdlen;

structinstancePrng*inst=malloc(sizeof(structinstancePrng));

if(!inst){

epicsPrintf(\"OutofMemoryn\");

gotoerror;

}

/*sizeof(dpreg)==strlen(dpref)+1*/

dlen=sizeof(dpref)+strlen(dist);

dname=malloc(dlen);

if(!dname){

epicsPrintf(\"OutofMemoryn\");

gotoerror;

}

strcpy(dname,dpref);

strcat(dname,dist);

SomeboilerplateforallocationandconstructionoftheDriverSupportnamestring.

inst->table=(structdrvPrngDist*)registryDriverSupportFind(dname);

if(!inst->table){

epicsPrintf(\"UnknownDistributiontypen\");

gotoerror;

}

WhenaDriverSupportisregisteredwitharunningIOCitsnameisplacedinalistwhichcanbequeriedwiththe

waythedistargumentisusedtoselectwhichDriverSupportistobeused.

SincethetwoDriverSupportsarecalleddrvPrngUniformanddrvPrngGaussianthetwovalidvaluesforthedistargumentare

‘Uniform’and‘Gaussian’.

inst->token=inst->table->create_prng(s);

if(!inst->token){

epicsPrintf(\"FailedtocreatePRNG.n\");

gotoerror;

}

TheDriverSupportcreatefunctionisusedtocreateanewinstancetoken.

inst->id=id;

e旷日持久是贬义词吗 llAdd(&devices,&inst->node);

return;

error:

free(dname);

free(inst);

return;

}

Allthatremainsistoaddtheinstancetothedeviceslistsothelookupfunctioncan?ndit.

atesthroughthelistofinstancesuntilit?ndsamatch.

structinstancePrng*lookupPrng(shortN)

{

ELLNODE*node;

structinstancePrng*ent;

for(node=ellFirst(&devices);node;node=ellNext(node)){

ent=(structinstancePrng*)node;/*UseCONTAINER()in3.14.11*/

if(ent->id==N)

returnent;

}

returnNULL;

}

11.4DeviceSupport

NowweturntotheDeviceSupportfunctionsfortheAIrecordtype(prngApp/src/devprngdist.c).Inthiscasetheinit_recordand

read_lythiswouldbeasignthatthetaskistoo

simpletobeni?tfromDriverSupportandsuggeststhatweinsteadcreatetwodifferentDeviceSupports.

staticlonginit_record(aiRecord*pao)

{

structinstancePrng*priv;

priv=lookupPrng(pao->);

if(!priv){

recGblRecordError(S_dev_noDevice,(void*)pao,

\"Notavaliddeviceidcode\");

returnS_dev_noDevice;

}

pao->dpvt=priv;

return0;

}

HereweusethelookupPrngfunctionwith(partof)ecardvalueisusedbecausenothingmoreis

needed.

IffoundtheinstanceisstoredintheDeviceSupportPrivate?eldforfutureuse.

staticlongread_ai(aiReco李清照的词一剪梅 rd*pao)

{

structinstancePrng*priv=pao->dpvt;

pao->rval=priv->table->read_prng(priv->token);

return0;

}

Toreadarandomnumberweusethereadfunctioninthefunctiontablestoredwiththeinstanceandpassittheinstance

tokenwhichwascreatedwiththecreatefunctionalsointhistable.

11.5DriverSupport(Uniform)

Wewillde??rstwillgeneraterandomnumbersinauniformdistribution(prngApp/src/drvprngu-

nif.c).

structuniform{

unsignedintstate;

};

Firstwede?effectivelytheprivatedataofthedrvPrngDist

ertothisstructurewillactastheinstance‘token’.

static

void*create(unsignedintseed)

{

structuniform*priv=malloc(sizeof(structuniform));

if(!priv)

returnNULL;

priv->state=seed;

returnpriv;

}

static

intread(void*tok)

{

structuniform*priv=tok;

returnrand_r(&priv->state);

}

static

structdrvPrngDistdrvPrngUniform={

{4,

NULL,

NULL,

},

create,

read,

};

epicsExportAddress(drvet,drvPrngUniform);

Theactualde?nitionofthisDriverSupportisstraightforward.

11.6DriverSupport(Gaussian)

WhilethedifferencebetweentheGaussianandUniformgeneratorsissmalltheyareplacedinseperate?lestodemonstrate

thatthetwoDriverSupportscanbecompletelyisolatedfromeachother.

structgaussian{

unsignedintstate;

};

static

void*create(unsignedintseed)

{

structgaussian*priv=malloc(sizeof(structgaussian));

if(!priv)

returnNULL;

priv->state=seed;

returnpriv;

}

static

intread(void*tok)

{

structgaussian*priv=tok;

intret=0,i=8;

while(i--)

ret+=rand_r(&priv->state)/8;

returnret;

}

ToapproximateaGaussiandistribution,severaluniformrandomnumbersaresummedinaccordancewiththeCentralLimit

Theorem.

static

structdrvPrngDistdrvPrngGaussian={{4,

NULL,

NULL,

},

create,

read,

};

epicsExportAddress(drvet,drvPrngGaussian);