BSP Developer's Guide

G
Upgrading 4.3 BSD Network Drivers
The first function pointer references this driver’s init( ) routine, which this driver
does not need or have. The second function pointer references the driver’s ioctl( )
interface, which allows the upper layer to manipulate the device state. The third
function pointer references the routine that outputs packets on the physical
medium. The last function pointer references a routine that can reset the device if
the TCP/IP stack decides that this needs to be done.
In 4.4 BSD, there is a generic output routine called ether_output( ) that all Ethernet
device drivers can use. Thus, to convert the above ether_attach( ) call to a 4.4-style
call, you would call ether_attach( ) as follows:
ether_attach(
(IFNET *) & pDrvCtrl->idr,
unit,
"xx",
(FUNCPTR) NULL,
(FUNCPTR) xxIoctl,
(FUNCPTR) ether_output, /* generic ether_output */
(FUNCPTR) xxReset
);
pDrvCtrl->idr.ac_if.if_start = (FUNCPTR)xxTxStartup;
This time, there is an extra line following the call to ether_attach( ). This line of
code adds a transmit startup routine to the Interface Data Record. The transmit
startup routine is called by the TCP/IP stack after the generic ether_output( )
routine is called. This extra line of code assumes that the driver already has a
transmit startup routine. If a driver lacks a separate transmit startup routine, you
must write one. See the template in G.2.4 Creating a Transmit Startup Routine.
G
G.2.1 Removing the xxOutput( ) Routine
If a 4.3 BSD driver has an xxOutput( ) routine, it should look something like the
following:
static int xxOutput
(
IDR * pIDR,
MBUF * pMbuf,
SOCK * pDestAddr
)
{
return (ether_output ((IFNET *)pIDR,pMbuf, pDestAddr,
(FUNCPTR) xxTxStartup, pIDR));
}
Internally, this routine calls the ether_output( ) routine, which expects a pointer to
the startup routine as one of its arguments. However, in the 4.4 BSD model, all that
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