.\" $NetBSD: pci_intr.9,v 1.1 2000/12/28 23:06:08 sommerfeld Exp $
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.Dd December 27, 2000
.Dt PCI_INTR 9
.Os
.Sh NAME
.Nm pci_intr ,
.Nm pci_intr_map ,
.Nm pci_intr_string ,
.Nm pci_intr_establish ,
.Nm pci_intr_disestablish
.Nd PCI bus interrupt manipulation functions.
.Sh SYNOPSIS
.Fd #include <dev/pci/pcivar.h>
.Ft int
.Fn pci_intr_map "struct pci_attach_args *pa" "pci_intr_handle_t *ih"
.Ft const char *
.Fn pci_intr_string "pci_chipset_t *pc" "pci_intr_handle_t ih"
.Ft void *
.Fn pci_intr_establish "pci_chipset_t *pc" "pci_intr_handle_t ih" \
"int ipl" "int (*intrhand)(void *)" "void *intrarg"
.Ft void
.Fn pci_intr_disestablish "pci_chipset_t *pc" "void *ih"
.Sh DESCRIPTION
.Pp
The 
.Nm
functions exist to allow device drivers machine-independant access to
PCI bus interrupts.  The functions described in this page are
typically declared in a port's
.Pa Aq machine/pci_machdep.h
header file; however, drivers should generally include 
.Pa Aq dev/pci/pcivar.h
to get other PCI-specific declarations as well.
.Pp
Each driver has an
.Fn attach
function which has a bus-specific 
.Ft attach_args
structure. 
Each driver for a PCI device is is passed a pointer to an object of type
.Ft 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.  
.Pp
If a driver wishes to establish an interrupt handler for the device,
it should pass the 
.Ft struct pci_attach_args *
to the
.Fn pci_intr_map 
function, which returns zero on success, and nonzero on failure.  The function
sets the
.Ft "pci_intr_handle_t"
pointed at by its second argument to a machine-dependant value which
identifies a particular interrupt source.
.Pp
If the driver wishes to refer to the interrupt source in an attach or
error message, it should use the value returned by
.Fn pci_intr_string .
.Pp
Subsequently, when the driver is prepared to recieve interrupts, it
should call 
.Fn pci_intr_establish
to actually establish the handler; when the device interrupts,
.Fa intrhand 
will be called with a single argument
.Fa intrarg ,
and will run at the interrupt priority level
.Fa ipl .
.Pp
The return value of
.Fn pci_intr_establish
may be saved and passed to 
.Fn pci_intr_disestablish 
to disable the interrupt handler
when the driver is no longer interested in interrupts from the device.