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13.1.8 Indicating That the Interrupt Was Serviced
The following code shows how the el_intr( ) routine indicates that the
interrupt was serviced:
return INTR_SERVICED; 1
}
1
Returns the INTR_SERVICED constant to the kernel interrupt
dispatcher to indicate that el_intr( ) serviced the shared interrupt.
13.2 Implementing the el_rint Routine
The if_el driver’s el_rint( ) routine is the receive interrupt completion
routine. It performs the following tasks:
• Counts the receive interrupt and reads the receive status (Section 13.2.1)
• Pulls the packets from the FIFO buffer (Section 13.2.2)
• Examines the first part of the packet (Section 13.2.3)
• Copies the received packet into the mbuf (Section 13.2.4)
• Discards a packet (Section 13.2.5)
13.2.1 Counting the Receive Interrupt and Reading the Receive
Status
The following code shows how the el_rint( ) routine counts the receive
interrupt and reads the receive status:
#define RXLOOP ((16*1024)/64)
1
static void el_rint(struct el_softc *sc,
struct ifnet *ifp)
{
int len, i, count=RXLOOP;
volatile short status;
struct mbuf *m;
unsigned char *dat;
unsigned int in;
struct ether_header eh;
sc->rint++;
2
status = READ_RXS(sc); 3
1 Defines a constant that represents the maximum number of packets in
a 16K receive buffer.
2 Increments the receive interrupt counter.
3 Calls the READ_RXS macro to read the receive status.
Implementing the Interrupt Section 13–5