Technical Q&A's

NW 05 - Ethernet Addresses (1-May-95)

Q How can I obtain an Ethernet address programmatically? I can get correct Ethernet addresses for RAM-based drivers, but this does not appear to work for all drivers. For example, addresses for PowerBooks with DaynaPort connections are not available. I am using the following code to obtain Ethernet addresses:


	myErr = OpenDriver("\p.ENET", &myRefNum);
	theEPB.EParms1.ioRefNum = myRefNum;
	
	theEPB.EParms1.ePointer = NewPtrClear(78);
	theEPB.EParms1.eBuffSize = 78;
	theEPB.EParms1.ioNamePtr = NULL;
	myErr = EGetInfo(&theEPB,false);

How can I scan through all the installed Ethernet drivers for the one that's active and obtain information about that one?

A Your approach for obtaining Ethernet address information seems appropriate. Here are a few pieces of information that may help:

1. OpenDriver("\p.ENET", &myRefNum) only opens the first Ethernet driver. If the system has more than one Ethernet card installed, you have to open them explicitly.

2. Machines such as the SE and PowerBooks that have the Ethernet hardware connected via the SCSI port are accessed through ENET0 (most machines have this ability).

The following is a code fragment that you can use:

/* check internal non slotted card 
   check if enet0 driver is installed 
*/

 short 	saveRes;		
	saveRes = LMGetResLoad();
	LMSetResLoad(0)
	GetNamedResource('DRVR',"\p.ENET0");   // check if ENET0 is in ROM 
	LMSetResLoad(saveRes)
	if(!ResError()) {
		
/* Setup Open PB */
	PB.slotDevParam.ioNamePtr  = "\p.ENET0";   // Attempt to open it
	PB.slotDevParam.ioVRefNum	= 0;
	PB.slotDevParam.csCode		= 0;
	PB.slotDevParam.ioSlot		= 0;
	PB.slotDevParam.ioID		= 0;
	
/* try and open the internal non slotted enet card */
	ErrNo = PBOpenSync(&PB);   // notice I do a regular open call $A000
	refnum = PB.ioRefNum;

3. For NuBus and SE30 devices (and PCI slots), you have to use the Slot Manager to scan for available Ethernet cards, per this example:


/* Setup Open PB  for sloted device */
	PB.slotDevParam.ioNamePtr  = "\p.ENET";
	PB.slotDevParam.ioVRefNum	= 0;
	PB.slotDevParam.csCode		= 0;

/* try Slotmanger Call */
	if(!OSTrapAvailable (_SlotManager)) return(Error);

	SPB.spExtDev 	= 0;
	SPB.spCategory	= 4;		/* Network 	*/
	SPB.spCType		= 1 ;		/* EtherNet */
	SPB.spTBMask	= 0x3;			
	 
/* loop on each card */
	while((ErrNo = SNextTypeSRsrc(&SPB)) == noErr){
		PB.slotDevParam.ioSlot		= SPB.spSlot;
		PB.slotDevParam.ioID		= SPB.spID;

/* try and open the enet card */
		ErrNo = PBOpenImmed(&PB);       // Notice I Do an OpenImmed $A200
		refnum = PB.ioRefNum;
	
	}

4. An important point to consider: OpenDriver calls fail when Ethernet devices are not cabled or hooked up, so it's not possible to get the address of Ethernet cards that aren't hooked up.

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