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.Dd June 19, 2001
.Dt PCI 9
.Os
.Sh NAME
.Nm PCI ,
.Nm pci_conf_read ,
.Nm pci_conf_write ,
.Nm pci_conf_print ,
.Nm pci_get_capability ,
.Nm pci_mapreg_type ,
.Nm pci_mapreg_map ,
.Nm pci_mapreg_info ,
.Nm pci_intr_map ,
.Nm pci_intr_string ,
.Nm pci_intr_evcnt ,
.Nm pci_intr_establish ,
.Nm pci_intr_disestablish ,
.Nm pci_make_tag ,
.Nm pci_decompose_tag ,
.Nm pci_findvendor ,
.Nm pci_devinfo ,
.Nm PCI_VENDOR ,
.Nm PCI_PRODUCT ,
.Nm PCI_REVISION 
.Nd Peripheral Component Interconnect
.Sh SYNOPSIS
.Fd #include <machine/bus.h>
.Fd #include <dev/pci/pcivar.h>
.Fd #include <dev/pci/pcireg.h>
.Fd #include <dev/pci/pcidevs.h>
.Ft pcireg_t
.Fn pci_conf_read "pci_chipset_tag_t pc" "pcitag_t tag" "int reg"
.Ft void
.Fn pci_conf_write "pci_chipset_tag_t pc" "pcitag_t tag" "int reg" \
"pcireg_t val"
.Ft void
.Fn pci_conf_print "pci_chipset_tag_t pc" "pcitag_t tag" \
"void (*func)(pci_chipset_tag_t, pcitag_t, const pcireg_t *)"
.Ft int
.Fn pci_get_capability "pci_chipset_tag_t pc" "pcitag_t tag" \
"int capid" "int *offsetp" "pcireg_t *valuep"
.Ft pcireg_t
.Fn pci_mapreg_type "pci_chipset_tag_t pc" "pcitag_t tag" "int reg"
.Ft int
.Fn pci_mapreg_map "struct pci_attach_args *pa" "int reg" \
"pcireg_t type"  "int busflags" "bus_space_tag_t *tagp" \
"bus_space_handle_t *handlep" "bus_addr_t *basep" "bus_size_t *sizep"
.Ft int
.Fn pci_mapreg_info "pci_chipset_tag_t pc" "pcitag_t tag" "int reg" \
"pcireg_t type" "bus_addr_t *basep" "bus_size_t *sizep" "int *flagsp"
.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_tag_t pc" "pci_intr_handle_t ih"
.Ft const struct evcnt *
.Fn pci_intr_evcnt "pci_chipset_tag_t pc" "pci_intr_handle_t ih"
.Ft void *
.Fn pci_intr_establish "pci_chipset_tag_t pc" "pci_intr_handle_t ih" \
"int level" "int (*handler)(void *)" "void *arg"
.Ft void
.Fn pci_intr_disestablish "pci_chipset_tag_t pc" "void *ih"
.Ft pcitag_t
.Fn pci_make_tag "pci_chipset_tag_t pc" "int bus" "int device" \
"int function"
.Ft void
.Fn pci_decompose_tag "pci_chipset_tag_t pc" "pcitag_t tag" \
"int *busp" "int *devicep" "int *functionp"
.Ft char *
.Fn pci_findvendor "pcireg_t id"
.Ft void
.Fn pci_devinfo "pcireg_t id" "pcireg_t class" "int show" "char *cp"
.Ft int
.Fn PCI_VENDOR "pcireg_t id"
.Ft int
.Fn PCI_PRODUCT "pcireg_t id"
.Ft int
.Fn PCI_REVISION "pcireg_t id"
.Sh DESCRIPTION
The machine-independent
.Nm
subsystem provides support for PCI devices.
.Pp
The PCI bus was initially developed by Intel in the early 1990's to
replace the ISA bus for interfacing to their Pentium processor.  The
PCI specification is widely regarded as well designed, and the PCI bus
has found widespread acceptable in machines ranging from Apple's
PowerPC-based machines to Sun's UltraSPARC-based machines.
.Pp
The PCI bus a multiplexed bus, allowing addresses and data on the same
pins for a reduced number of pins.  Data transfers can be 8-bit,
16-bit or 32-bit.  A 64-bit extended PCI bus is also defined.
Multi-byte transfers are little-endian.  The PCI bus operates up to
33MHz and any device on the bus can be the bus master.
.Pp
AGP is a version of PCI optimised for high-throughput data rates,
particularly for accelerated frame buffers.
.Pp
The PCI bus is a "plug and play" bus, in the sense that devices can be
configured dynamically by software.  The PCI interface chip on a PCI
device bus presents a small window of registers into the PCI
configuration space.  These registers contain information about the
device such as the vendor and a product ID.  The configuration
registers can also be written to by software to alter how the device
interfaces to the PCI bus.  An important register in the configuration
space is the Base Address Register (BAR).  The BAR is written by
software to map the device registers into a window of processor
address space.  Once this mapping is done, the device registers can be
accessed relative to the base address.
.Sh DATA TYPES
Drivers for devices attached to the
.Nm
will make use of the following data types:
.Bl -tag -width compact
.It Fa pcireg_t
Configuration space register.
.It Fa pci_chipset_tag_t
Chipset tag for the PCI bus.
.It Fa pcitag_t
Configuration tag describing the location and function of the PCI
device.  It contains the tuple
.Ao
bus, device, function
.Ac . 
.It Fa pci_intr_handle_t
The opaque handle describing an established interrupt handler.
.It Fa struct pci_attach_args
Devices have their identity recorded in this structure.  it contains
the following members:
.Bd -literal
	bus_space_tag_t pa_iot;		/* pci i/o space tag */
	bus_space_tag_t pa_memt;	/* pci mem space tag */
	bus_dma_tag_t pa_dmat;		/* DMA tag */
	pci_chipset_tag_t pa_pc;
	int pa_flags;			/* flags */
	pcitag_t pa_tag;
	pcireg_t pa_id;
	pcireg_t pa_class;
.Ed
.El
.Sh FUNCTIONS
.Bl -tag -width compact
.It Fn pci_conf_read "pc" "tag" "reg"
Read from register
.Fa reg
in PCI configuration space.  The argument
.Fa tag
is the PCI tag for the current device attached to PCI chipset
.Fa pc .
.It Fn pci_conf_write "pc" "tag" "reg" "val"
Write to register
.Fa reg
in PCI configuration space.  The argument
.Fa tag
is the PCI tag for the current device attached to PCI chipset
.Fa pc .
.It Fn pci_conf_print "pc" "tag" "func"
Print out most of the registers in the PCI configuration for the
device.  The argument
.Fa tag
is the PCI tag for the current device attached to PCI chipset
.Fa pc .
The argument
.Fa func
is a function called by
.Fn pci_conf_print
to print the device-dependent registers.  This function is only useful
for driver development and is usually wrapped in pre-processor
declarations.
.It Fn pci_get_capability "pc" "tag" "capid" "offsetp" "valuep"
Parse the device capability list in configuration space looking for
capability
.Fa capid .
If
.Fa offsetp
is not NULL, the register offset in configuration space is returned in
.Fa offsetp.
If
.Fa valuep
is not NULL, the value of the capability is returned in
.Fa valuep .
The argument
.Fa tag
is the PCI tag for the current device attached to PCI chipset
.Fa pc .
This function returns 1 if the capability was found.  If the
capability was not found, it returns zero, and
.Fa offsetp
and
.Fa valuep
remain unchanged.
.It Fn pci_mapreg_type "pc" "tag" "reg"
Interrogates the Base Address Register (BAR) in configuration space
specified by
.Fa reg
and returns the default (or current) mapping type.  Valid returns
values are:
.Bl -tag -width compact
.It PCI_MAPREG_TYPE_IO
The mapping is to I/O address space.
.It PCI_MAPREG_TYPE_MEM
The mapping is to memory address space.
.It PCI_MAPREG_TYPE_MEM | PCI_MAPREG_MEM_TYPE_64BIT
The mapping is to 64-bit memory address space.
.It PCI_MAPREG_TYPE_ROM
The mapping is to ROM.
.El
.sp
The argument
.Fa tag
is the PCI tag for the current device attached to PCI chipset
.Fa pc .
.It Fo pci_mapreg_map
.Fa "pa" "reg" "type"  "busflags" "tagp" "handlep"
.Fa "basep" "sizep"
.Fc
Maps the register windows for the device into kernel virtual address
space.  This function is generally only called during the driver
attach step and takes a pointer to the
.Em struct pci_attach_args
in
.Fa pa .
The physical address of the mapping is in the Base Address Register
(BAR) in configuration space specified by
.Fa reg .
Valid values for the type of mapping
.Fa type
are:
.Bl -tag -width compact
.It PCI_MAPREG_TYPE_IO
The mapping should be to I/O address space.
.It PCI_MAPREG_TYPE_MEM
The mapping should be to memory address space.
.It PCI_MAPREG_TYPE_ROM
The mapping is to access ROM.
.El
.sp
The argument
.Fa busflags
are bus-space flags passed to
.Fn bus_space_map
to perform the mapping (see
.Xr bus_space 9 ).
The bus-space tag and handle for the mapped register window are
returned in
.Fa tagp
and
.Fa handlep
respectively.  The bus-address and size of the mapping are returned in
.Fa basep
and
.Fa sizep
respectively.  If any of
.Fa tagp ,
.Fa handlep ,
.Fa basep ,
or
.Fa sizep
are NULL then
.Fn pci_mapreg_map
does not define their return value.  This function returns zero on
success and non-zero on error.
.It Fn pci_mapreg_info "pc" "tag" "reg" "type" "basep" "sizep" "flagsp"
Performs the same operations as
.Fn pci_mapreg_map
but doesn't actually map the register window into kernel virtual
address space.  Returns the bus-address, size and bus flags in
.Fa basep ,
.Fa sizep
and
.Fa flagsp
respectively.  These return values can be used by
.Fn bus_space_map
to actually map the register window into kernel virtual address space.
This function is useful for setting up the registers in configuration
space and deferring the mapping to a later time, such as in a
bus-independent attachment routine.
.Fa pci_mapreg_info
returns zero on success and non-zero on failure.
.It Fn pci_intr_map "pa" "ih"
See
.Xr pci_intr 9 .
.It Fn pci_intr_string "pc" "ih"
See
.Xr pci_intr 9 .
.It Fn pci_intr_evcnt "pc" "ih"
See
.Xr pci_intr 9 .
.It Fn pci_intr_establish "pc" "ih" "level" "handler" "arg"
See
.Xr pci_intr 9 .
.It Fn pci_intr_disestablish "pc" "ih"
See
.Xr pci_intr 9 .
.It Fn pci_make_tag "pc" "bus" "device" "function"
Create a new PCI tag for the PCI device specified by the tuple
.Ao
bus, device, function
.Ac .
This function is not useful to the usual PCI device driver.  It is
generally used by drivers of multi-function devices when attaching
other PCI device drivers to each function.
.It Fn pci_decompose_tag "pc" "tag" "busp" "devicep" "fnp"
Decompose the PCI tag
.Fa tag
generated by
.Fn pci_make_tag
into its
.Ao
bus, device, function
.Ac
tuple.
.It Fn pci_findvendor "id"
Return the string of the vendor name for the device specified by
.Fa id .
.It Fn pci_devinfo "id" "class" "show" "cp"
Returns the description string from the in-kernel PCI database for the
device described by
.Fa id
and
.Fa class .
The description string is returned in
.Fa cp .
The argument
.Fa show
specifies whether the PCI subsystem should report the string to the
console.
.It Fn PCI_VENDOR "id"
Return the PCI vendor id for device
.Fa id .
.It Fn PCI_PRODUCT "id"
Return the PCI product id for device
.Fa id .
.It Fn PCI_REVISION "id"
Return the PCI product revision for device
.Fa id .
.El
.Sh AUTOCONFIGURATION
During autoconfiguration, a
.Nm
driver will receive a pointer to
.Fa struct pci_attach_args
describing the device attaches to the PCI bus.  Drivers match the
device using the
.Fa pa_id
member using
.Fn PCI_VENDOR .
.Fn PCI_PRODUCT
and
.Fn PCI_REVISION .
.Pp
During the driver attach step, drivers can read the device
configuration space using
.Fn pci_conf_read .
The meaning attached to registers in the PCI configuration space are
device-dependent, but will usually contain physical addresses of the
device register windows.  Device options can also be stored into the
PCI configuration space using
.Fn pci_conf_write .
For example, the driver can request support for bus-mastering DMA by
writing the option to the PCI configuration space.
.Pp
Device capabilities can be queried using
.Fn pci_get_capability ,
and returns device-specific information which can be found in the PCI
configuration space to alter device operation.
.Pp
After reading the physical addresses of the device register windows
from configuration space, these windows must be mapped into kernel
virtual address space using
.Fn pci_mapreg_map .
Device registers can now be accessed using the standard bus-space API
(see
.Xr bus_space 9 ).
.Pp
Details of using PCI interrupts is described in
.Xr pci_intr 9 .
.Sh DMA SUPPORT
The PCI bus supports bus-mastering operations from any device on the
bus.  The DMA facilities are accessed through the standard
.Xr bus_dma 9
interface.  To support DMA transfers from the device to the host, it
is necessary to enable bus-mastering in the PCI configuration space
for the device.
.Pp
During system shutdown, it is necessary to abort any DMA transfers in
progress by registering a shutdown hook (see
.Xr shutdownhook_establish 9 ).
.Sh CODE REFERENCES
This section describes places within the
.Nx
source tree where actual code implementing or utilising the
machine-independent PCI subsystem can be found.  All pathnames are
relative to
.Pa /usr/src.
.Pp
The PCI subsystem itself is implemented within the files
.Pa sys/dev/pci/pci.c ,
.Pa sys/dev/pci/pci_subr.c ,
.Pa sys/dev/pci/pci_map.c ,
.Pa sys/dev/pci/pci_quirks.c ,
and
.Pa sys/dev/pci/pciconf.c .
Machine-dependent portions are implemented within the file
.Pa sys/arch/<arch>/pci/pci_machdep.c .
.Pp
The database of known devices exists within the file
.Pa sys/dev/pci/pcidevs_data.h
and is generated automatically from the file
.Pa sys/dev/pci/pcidevs .
New vendor and product identifiers should be added to this
file.  The database can be regenerated using the Makefile
.Pa sys/dev/pci/Makefile.pcidevs .
.Sh SEE ALSO
.Xr pci 4 ,
.Xr autoconf 9 ,
.Xr bus_dma 9 ,
.Xr bus_space 9 ,
.Xr driver 9 ,
.Xr pci_configure_bus 9 ,
.Xr pci_intr 9 ,
.Xr shutdownhook_establish 9 .
.Sh HISTORY
The machine-independent PCI subsystem appeared in
.Nx 1.2 .