SVR5 and SCO OpenServer

intr(D2mdi)

intr -- process an MDI device interrupt

Syntax

See intr(D2) for syntax, context, and general usage information about this entry point routine in DDI drivers.

See intr(D2oddi) for syntax, context, and general usage information about this entry point routine in ODDI drivers.

Usage

The intr( ) entry point routine is called when the network adapter generates an interrupt. It may also be called if another device shares this interrupt vector with the MDI driver. It is extremely important that an MDI driver spends a small amount of time in its interrupt handler so that system performance is not adversely affected.

The intr( ) routine can be called immediately after the cm_intr_attach(D3) or mod_drvattach(D3) routines.

The MDI driver should perform the following processing:

Check whether the interrupt was generated by the MDI device or another device that shares this interrupt. If the MDI device did not generate the interrupt, return.
Filter out any frames based on the destination MAC address. The destination MAC address must be one of:
- The broadcast MAC address
- A MAC address in the multicast address table. For more information see MACIOC_SETMCA, MACIOC_SETALLMCA, and mdi_valid_mca(D3mdi).
- The adapter's MAC address
If this is a received frame interrupt, allocate a single STREAMS message block large enough to hold the received frame
Copy the frame from the adapter into the STREAMS block
Call the putnext(D3str) function to hand this message to the next module upstream

Additional processing can occur in the intr( ) entry point routine if the service from interrupt algorithm is implemented; see ``Increasing transmit performance'' in Developing MDI network adapter drivers.

If the driver is used on a smart-bus system (that is, PCI, EISA, or MCA), your interrupt routine can be called if interrupts are shared with another device. In this case, you must check all of your devices using the interrupt to see if it is yours.

For DDI 7 drivers, when you find one instance of your hardware at a particular interrupt, be sure to keep searching; another instance of your hardware may also be using that interrupt.

MDI drivers generally should not make use of a STREAMS read srv(D2str) routine; inbound frames should be passed up at interrupt time.

If a spurious interrupt occurs, the MDI driver should increment the count of spurious interrupts in its statistics structure (see mac_stats_eth(D4mdi), mac_stats_fddi(D4mdi), and mac_stats_tr(D4mdi)) and exit from the interrupt routine as soon as possible. Spurious interrupts occur when one of the following is true:

The driver has not been opened.
The driver has not been bound with the MAC_BIND_REQ(D7mdi) message type.
The interrupt was not expected (in other words, the Interrupt Status Register did not indicate that anything needed to be done)

To mask interrupts from the network adapter, MDI drivers should use an appropriate lock function or the kernel function splstr(D3). Do not use splhi, intr_disable, or the 80?86 STI/CLI instructions.

Do not assume that all interrupts are in the range 0-15 or 0-31. For example, interrupt numbers can be up to 255 on APIC PCI machines. It is preferable to store the interrupt in the per-device structure(s) and search them for interrupt matches, rather than declaring a static array of interrupt vectors.

Version applicability

mdi: 1, 2, 2.1 running with ddi: 7, 7mp, 8, 8mp.

References

intr(D2), intr(D2oddi), mdi_get_unit(D3mdi), mdi_valid_mca(D3mdi), Intro(MDI) manual page on OpenServer 6 and the Intro(7mdi) manual page on UnixWare 7.1.4.

``MAC addresses'' in HDK Technical Reference, ``Spin locks (DDI)'' in HDK Technical Reference