May 19, 2002 PCI_INTR 9

### NAME

pci_intr, pci_intr_map, pci_intr_string, pci_intr_establish, pci_intr_disestablish - PCI bus interrupt manipulation functions

### SYNOPSIS

```int` pci_intr_map(```struct pci_attach_args *pa``, pci_intr_handle_t *ih`)
```const` `char``*` pci_intr_string(```pci_chipset_t *pc``, pci_intr_handle_t ih`)
```void``*` pci_intr_establish(```pci_chipset_t *pc``, pci_intr_handle_t ih``, int ipl``, int (*intrhand)(void *)``, void *intrarg`)
```void` pci_intr_disestablish(```pci_chipset_t *pc``, void *ih`)

### DESCRIPTION

The pci_intr functions exist to allow device drivers machine-independent access to PCI bus interrupts. The functions described in this page are typically declared in a port's <```machine/pci_machdep.h`> header file; however, drivers should generally include <```dev/pci/pcivar.h`> to get other PCI-specific declarations as well.

Each driver has an attach(``) function which has a bus-specific
```attach_args` structure. Each driver for a PCI device is passed a pointer to an object of type
```struct` `pci_attach_args` which contains, among other things, information about the location of the device in the PCI bus topology sufficient to allow interrupts from the device to be handled.

If a driver wishes to establish an interrupt handler for the device, it should pass the
```struct` `pci_attach_args``*` to the pci_intr_map(``) function, which returns zero on success, and nonzero on failure. The function sets the
```pci_intr_handle_t` pointed at by its second argument to a machine-dependent value which identifies a particular interrupt source.

If the driver wishes to refer to the interrupt source in an attach or error message, it should use the value returned by pci_intr_string(``).

Subsequently, when the driver is prepared to receive interrupts, it should call pci_intr_establish(``) to actually establish the handler; when the device interrupts, ```intrhand` will be called with a single argument ```intrarg`, and will run at the interrupt priority level ```ipl`.

The return value of pci_intr_establish(``) may be saved and passed to pci_intr_disestablish(``) to disable the interrupt handler when the driver is no longer interested in interrupts from the device.

#### PORTING

A port's implementation of pci_intr_map(``) may use the following members of
```struct` `pci_attach_args` to determine how the device's interrupts are routed. `

            pci_chipset_tag_t pa_pc;
            pcitag_t pa_tag;
            pcitag_t pa_intrtag; /* intr. appears to come from here */
            pci_intr_pin_t pa_intrpin; /* intr. appears on this pin */
            pci_intr_line_t pa_intrline; /* intr. routing information */
            pci_intr_pin_t pa_rawintrpin; /* unswizzled pin */

`

PCI-PCI bridges swizzle (permute) interrupt wiring. Depending on implementation details, it may be more convenient to use either original or the swizzled interrupt parameters. The original device tag and interrupt pin can be found in
```pa_tag` and
```pa_rawintrpin` respectively, while the swizzled tag and pin can be found in
```pa_intrtag` and
```pa_intrpin`.

When a device is attached to a primary bus, both pairs of fields contain the same values. When a device is found behind one or more pci-pci bridges,
```pa_intrpin` contains the ``swizzled'' interrupt pin number, while
```pa_rawintrpin` contains the original interrupt pin;
```pa_tag` contains the PCI tag of the device itself, and
```pa_intrtag` contains the PCI tag of the uppermost bridge device.