epics record/device/driver support [email protected], many slides copied from [email protected]
TRANSCRIPT
Interfacing Hardware
Hardware
“Driver”
Software
General Idea
Hardware
Device Support
IOC Core: Db, CA, …
EPICS
Driver Support
Record Support
Where to extend… Common Case: New Hardware (I/O Board,..)
Driver: Any low-level code to talk to the hardware.Might not have any knowledge of EPICS
Device: EPICS-specific glue code between driver and (subset of) records
Sometimes: Specialized Record Copy of existing record w/ slight change
Seldom: New Record Type Can task be handled by combination of existing
records, maybe w/ help of SNL?
Driver/Device/Record Support Read the “IOC Application Developer's Guide”
before even thinking about doing this! Common Idea:
Describe the new driver/device/record via DBD (Database Description File, ASCII)
Implement the functionality, providing a function table specific to driver/device/record support (init(), report(), do_something(), …)
Link/load the binaries which export a function table During startup, iocCore will parse the DBD,
locate the function table and invoke the appropriate functions
Well-defined interfaces for adding new support, minimal recompilation.
Driver Support Drivers can be complicated:
Bus-level access, critical timing, interrupts, semaphores, threads, deadlocks, fail-safe, OS-specific (vxWorks, Linux, Win32), …
Typical collection of routines:Check, report, init, read, write, setup_trigger(callback),…
“EPICS part”: Optional & Trivial!
Driver Support Entry Table
/* EPICS Base include file <drvSup.h> */
typedef long (*DRVSUPFUN) ();
struct drvet
{
long number; /*number of support routines*/DRVSUPFUN report; /*print report*/DRVSUPFUN init; /*init the driver */
};
Any routine pointer can be NULL
DSET Example/* xy.c */#include<drvSup.h>
static long xy_report(){
printf(“XY Driver Info:\n); …} static long xy_init(){
if (xy_check()) { …} struct drvet drvXy ={
2, xy_report,
xy_init};
Registering Driver w/ EPICS EPICS DBD File Entry
driver(drvXy) Results:
EPICS iocInit will locate “drvXy” in symbol table, call the registered “init” routine (unless NULL)
EPICS dbior will invoke “report” routine (unless NULL)
Good Practice Wrong: Assume e.g. two XY board, one
at base address 0x1234 and one at 0x4567, all hard-coded in driver.
Best: Provide “configure” routine, callable from e.g. vxWorks startup file before invoking iocInit:
# EPICS records that refer to XY #0 will
# access board at base addr. 0xfe12# in mode 15xy_config(0, 0xfe12, 15)
Device Support Glue between record and driver is highly
specific to the resp. record: AI record, DTYP=“XY”, INP=“#C0 S5”:
Device support has to call driver for “XY” card #0 and get signal #5 into the record’s RVAL field
Dev.sup routines common to all records: Report: Show info Init: Called once Init_Record: Called for each record Get I/O Interrupt Info: Used w/ SCAN=“I/O Intr”Most are optional, but check specific record type.
Device Support Entry Table
/* Defined in devSup.h */
struct dset
{
long number; /* number of support routines */
DEVSUPFUN report; /* print report*/
DEVSUPFUN init; /* init support*/
DEVSUPFUN init_record; /* init particular record */
DEVSUPFUN get_ioint_info; /* get I/O Intr. Info */
/* Rest specific to record, e.g. BI:
DEVSUPFUN read_bi;
Result: (0,2,error) 0 -> raw value stored in RVAL, convert to VAL 2 -> value already stored in VAL, don’t convert
*/
}
Registering Device Support EPICS DBD File:
device(ai,INST_IO,devAiXX,“My XX")
Result: iocCore … now allows DTYP=“My XX” for ai records will locate DSET “devAiXX” in symbol
table,call init(), then init_record() for each record, record will call read() whenever record gets processed, …
Before Implementing Dev.Sup Understand how to use the driver Read
“Application Developer Guide” Source for specific record type XX,
understand how record calls its device support
Examples in EPICS base sources: base/src/dev/softDev/devXXSoft.c
Device Support for AI Record Common
report initialization initialize instance attach to device
interrupt
AI-Specific read ai device
value linear conversion
(RVAL->VAL)
AI Device Support Type Initializationlong aiDevInit (unsigned pass) common to all record types device specific initialization pass = 0, prior to initializing each record
during "iocInit()“ Check hardware, …
but note that records are not ready to handle data
pass = 1, after initializing each record during "iocInit()“ Activate triggers, …
AI Device Report
long aiDevReport (struct aiRecord * pai, int level);
common to all records, but gets passed pointer to specific record type
called once for every record instance when the user types "dbior <level>"
device status to "stdout" from this routine Idea: detail increases with increasing
"level"
AI Device Initialization for Record long aiDevInitInstance(struct aiRecord *pai)
Called from within “iocInit()” once for each record attached to device
Typical Parse & check device address (pai->inp) Store device-data, e.g. the parsed signal #,
driver handles, … in DPVT:pvt = (X *) calloc(1, sizeof(X);pvt->signal = signal_this_record_wants;pvt->drv = magic_handle_we_got_from_driver;pai->dpvt = (void *) pvt;
Read Signal Value
long aiDevRead_(struct aiRecord * pai){long rval;if (device OK){
rval=pDevMemoryMap->aiRegister[pai->dpvt->signal];
pai->rval = rval;}else
recGblSetSevr(pai, READ_ALARM, INVALID_ALARM);
}
AI Linear Conversion
long aiDevLinearConv (struct aiRecord *pai, int after);
Setup the slope and offset for the conversion to engineering units
if (!after) return S_XXXX_OK;
/* A 12 bit DAC is assumed here */pai->eslo = (pai->eguf - pai->egul)/0x0FFF;pai->roff = 0;
/* roff could be different for device w/ e.g. +-5V, half scale = 0V */
From convert() in aiRecord.c
double val;val = pai->rval + pai->roff;/* * adjust with slope/offset * if linear convert is used */if ( pai->aslo != 0.0 ) val *= pai->aslo;if( pai->aoff != 0.0 ) val+= pai->aoff;
if(pai->linr == menuConvertLINEAR) val = (val * pai->eslo) + pai-
>eoff;
Advanced: Interrupts
Device supports interrupts, want to use SCAN=“I/O Intr”
higher scan rate scan synchronized with device
Difficulty Interrupts: interrupt level, most OS routines
prohibited Record processing: task level
IOSCANPVT EPICS Core Helper for processing records in response
to interrupt
IOSCANPVT
Initialize & keep one IOSCANPVT per distinct interrupt that the hardware can generate /* Record’s DPVT points to struct X* which contains IOCSCANPVT ioscanpvt */X = (X *) rec->dpvt;scanIoInit(&X->ioscanpvt);
Each Interrupt Occurrence (ISR):
scanIoRequest(X->ioscanpvt); safe to call from ISR, but don’t call
scanIoRequest() until after database init (“iocInit()”) completes(extern volatile int interruptAccept;)
Provide IO Interrupt Info
long aiDevGetIoIntInfo (int cmd, struct aiRecord *pai,IOSCANPVT *ppvt);
associates interrupt source with record
*ppvt = X->ioscanpvt; cmd==0 - insert into IO interrupt scan cmd==1 - remove from IO Interrupt
scan
Asynchronous Devices
read/write routine sets “PACT” true and returns zero for success.
asynchronous IO completion callback completes record processing
don’t process a record from within an ISR
Example Asynchronous Readlong devXxxRead (struct aiRecord *pai) {
if (pai->pact)return S_devXxx_OK; /* zero */
pai->pact = TRUEdevXxxBeginAsyncIO(pai->dpvt);return S_devXxx_OK;
}
Example Asynchronous Read Completionvoid devXxxAsyncIOCompletion(struct aiRecord *pai, long ioStatus){
struct rset *prset = (struct rset *) pai->rset;
dbScanLock(pai); if (ioStatus != S_devXxx_OK) {
recGblSetSevr(pai, READ_ALARM, INVALID_ALARM);}(*prset->process)(pai);dbScanUnlock(pai);
}
Record Support
Similar to device & driver support: Certain routines need to be implemented Binary exports a “Record support entry
table” which contains those routines DBD File to describe record and each field
(name, data type, maybe menu of enumerated values, …)
Record DBD File Need to read “IOC Application Developer's Guide”
to understand full DBD syntax! Use xxxRecord created by makeBaseApp as
example
recordtype(xxx){
# Each record needs to start w/ the common fields!include "dbCommon.dbd" field(VAL,DBF_DOUBLE)
{prompt("Current EGU Value")asl(ASL0)pp(TRUE)
}…
}
Record support entry table Initialization:
General and per-record instance Process routine:
Implements functionality of record. Often calls device support specific to this record type checks for alarms posts monitors processes forward links
Utility routines that allow iocCore to properly read, write & display fields of this record
Record support entry table… Record Implementation must export
struct rset <xxxRecord>RSET;struct rset /* record support entry table */{
long number; /* number of support routine */RECSUPFUN report; /* print report */RECSUPFUN init; /* init support */RECSUPFUN init_record; /* init record */RECSUPFUN process; /* process record */RECSUPFUN special; /* special processing */RECSUPFUN get_value; /* OBSOLETE: Just leave NULL */RECSUPFUN cvt_dbaddr; /* cvt dbAddr */RECSUPFUN get_array_info;RECSUPFUN put_array_info;RECSUPFUN get_units;RECSUPFUN get_precision;RECSUPFUN get_enum_str; /* get string from enum */RECSUPFUN get_enum_strs; /* get all enum strings */RECSUPFUN put_enum_str; /* put enum from string */RECSUPFUN get_graphic_double;RECSUPFUN get_control_double;RECSUPFUN get_alarm_double;
};
Initialization init()
Called once during IOC startup init_record(void *precord, int pass)
Called twice per record instance. Second pass can affect other records.
Processing Usually follows this example:static long process(void *precord){
xxxRecord*pxxx = (xxxRecord *)precord;xxxdset *pdset = (xxxdset *)pxxx->dset;long status;unsigned char pact=pxxx->pact;if( (pdset==NULL) || (pdset->read_xxx==NULL) ){
/* leave pact true so that dbProcess doesnt call again*/pxxx->pact=TRUE;recGblRecordError(S_dev_missingSup, pxxx, ”read_xxx”);return (S_dev_missingSup);
}/* pact must not be set true until read_xxx completes*/status=(*pdset->read_xxx)(pxxx); /* read the new value *//* return if beginning of asynch processing*/if(!pact && pxxx->pact) return(0);pxxx->pact = TRUE;recGblGetTimeStamp(pxxx);/* check for alarms */alarm(pxxx);/* check event list */monitor(pxxx);/* process the forward scan link record */recGblFwdLink(pxxx);pxxx->pact=FALSE;return(status);
}
Utility Routines Allow to define
how the record responds when fields are read or written
the units, precision, limits;not only of the VAL field!
Utility Routines… special(DBADDR *addr, int after)
Allows us to react before/after somebody else accesses field ref’ed by addr.
get_units(DBADDR *addr, char *units),get_precision(DBADDR *addr, long *prec),get_array_info(…) Can simply copy contents of EGU or PREC
fields,can also provide information specific to field ref’ed by addr