if ((sc->debug) && (count <= 0))
printf("el%d: Receive in INFINITE loop %04X\n", ifp->if_unit, status);
}
1 Calls the WRITE_CMD macro to write data to the command port register.
The data to be written is the receive discard top packet command
(CMD_RXDTP).
13.3 Implementing the el_tint Routine
The if_el device driver’s el_tint( ) routine is the transmit interrupt
completion routine. It performs the following tasks:
• Counts the transmit interrupt (Section 13.3.1)
• Reads the transmit status and counts all significant events
(Section 13.3.2)
• Manages excessive data collisions (Section 13.3.3)
• Writes to the status register to obtain the next value (Section 13.3.4)
• Queues other transmits (Section 13.3.5)
13.3.1 Counting the Transmit Interrupt
The following code shows how the el_tint( ) routine counts the transmit
interrupt:
#define TXLOOP ((16*1024)/64)
static void el_tint(struct el_softc *sc,
struct ifnet *ifp)
{
int count=TXLOOP;
volatile unsigned int status;
sc->tint++;
1
1 Increments a counter of the number of the transmit interrupts that
have been processed.
13.3.2 Reading the Transmit Status and Counting All Significant
Events
The following code shows how the el_tint( ) routine reads the transmit
status and counts all significant events:
status = READ_TXS(sc); 1
while ((status & (TX_CM<<8)) && (count-- > 0)) {
if (status & ((TX_JB|TX_UN)<<8)) {
2
ifp->if_oerrors++;
sc->ctrblk.est_sendfail++;
sc->txreset++;
WRITE_TXS(sc, status);
3
13–10 Implementing the Interrupt Section
