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PCI(4)			 BSD Kernel Interfaces Manual			PCI(4)

     pci -- generic PCI	driver

     device pci

     The pci driver provides a way for userland	programs to read and write PCI
     configuration registers.  It also provides	a way for userland programs to
     get a list	of all PCI devices, or all PCI devices that match various pat-

     Since the pci driver provides a write interface for PCI configuration
     registers,	system administrators should exercise caution when granting
     access to the pci device.	If used	improperly, this driver	can allow
     userland applications to crash a machine or cause data loss.

     It	is only	necessary to specify one pci controller	in the kernel.	Addi-
     tional PCI	busses are handled automatically as they are encountered.

     The following ioctl(2) calls are supported	by the pci driver.  They are
     defined in	the header file	<sys/pciio.h>.

     PCIOCGETCONF     This ioctl(2) takes a pci_conf_io	structure.  It allows
		      the user to retrieve information on all PCI devices in
		      the system, or on	PCI devices matching patterns supplied
		      by the user.  The	call may set errno to any value	speci-
		      fied in either copyin(9) or copyout(9).  The pci_conf_io
		      structure	consists of a number of	fields:

		      pat_buf_len    The length, in bytes, of the buffer
				     filled with user-supplied patterns.

		      num_patterns   The number	of user-supplied patterns.

		      patterns	     Pointer to	a buffer filled	with user-sup-
				     plied patterns.  patterns is a pointer to
				     num_patterns pci_match_conf structures.
				     The pci_match_conf	structure consists of
				     the following elements:

				     pc_sel	PCI domain, bus, slot and

				     pd_name	PCI device driver name.

				     pd_unit	PCI device driver unit number.

				     pc_vendor	PCI vendor ID.

				     pc_device	PCI device ID.

				     pc_class	PCI device class.

				     flags	The flags describe which of
						the fields the kernel should
						match against.	A device must
						match all specified fields in
						order to be returned.  The
						match flags are	enumerated in
						the pci_getconf_flags struc-
						ture.  Hopefully the flag val-
						ues are	obvious	enough that
						they do	not need to described
						in detail.

		      match_buf_len  Length of the matches buffer allocated by
				     the user to hold the results of the
				     PCIOCGETCONF query.

		      num_matches    Number of matches returned	by the kernel.

		      matches	     Buffer containing matching	devices	re-
				     turned by the kernel.  The	items in this
				     buffer are	of type	pci_conf, which	con-
				     sists of the following items:

				     pc_sel	   PCI domain, bus, slot and

				     pc_hdr	   PCI header type.

				     pc_subvendor  PCI subvendor ID.

				     pc_subdevice  PCI subdevice ID.

				     pc_vendor	   PCI vendor ID.

				     pc_device	   PCI device ID.

				     pc_class	   PCI device class.

				     pc_subclass   PCI device subclass.

				     pc_progif	   PCI device programming in-

				     pc_revid	   PCI revision	ID.

				     pd_name	   Driver name.

				     pd_unit	   Driver unit number.

		      offset	     The offset	is passed in by	the user to
				     tell the kernel where it should start
				     traversing	the device list.  The value
				     passed out	by the kernel points to	the
				     record immediately	after the last one re-
				     turned.  The user may pass	the value re-
				     turned by the kernel in subsequent	calls
				     to	the PCIOCGETCONF ioctl.	 If the	user
				     does not intend to	use the	offset,	it
				     must be set to zero.

		      generation     PCI configuration generation.  This value
				     only needs	to be set if the offset	is
				     set.  The kernel will compare the current
				     generation	number of its internal device
				     list to the generation passed in by the
				     user to determine whether its device list
				     has changed since the user	last called
				     the PCIOCGETCONF ioctl.  If the device
				     list has changed, a status	of
				     PCI_GETCONF_LIST_CHANGED will be passed

		      status	     The status	tells the user the disposition
				     of	his request for	a device list.	The
				     possible status values are:

				     This means	that there are no more devices
				     in	the PCI	device list after the ones re-
				     turned in the matches buffer.

				     This status tells the user	that the PCI
				     device list has changed since his last
				     call to the PCIOCGETCONF ioctl and	he
				     must reset	the offset and generation to
				     zero to start over	at the beginning of
				     the list.

				     This tells	the user that his buffer was
				     not large enough to hold all of the re-
				     maining devices in	the device list	that
				     possibly match his	criteria.  It is pos-
				     sible for this status to be returned,
				     even when none of the remaining devices
				     in	the list would match the user's	crite-

				     This indicates a general error while ser-
				     vicing the	user's request.	 If the
				     pat_buf_len is not	equal to num_patterns
				     times sizeof(struct pci_match_conf),
				     errno will	be set to EINVAL.

     PCIOCREAD	      This ioctl(2) reads the PCI configuration	registers
		      specified	by the passed-in pci_io	structure.  The	pci_io
		      structure	consists of the	following fields:

		      pi_sel	A pcisel structure which specifies the domain,
				bus, slot and function the user	would like to
				query.	If the specific	bus is not found, er-
				rno will be set	to ENODEV and -1 returned from
				the ioctl.

		      pi_reg	The PCI	configuration register the user	would
				like to	access.

		      pi_width	The width, in bytes, of	the data the user
				would like to read.  This value	may be either
				1, 2, or 4.  3-byte reads and reads larger
				than 4 bytes are not supported.	 If an invalid
				width is passed, errno will be set to EINVAL.

		      pi_data	The data returned by the kernel.

     PCIOCWRITE	      This ioctl(2) allows users to write to the PCI specified
		      in the passed-in pci_io structure.  The pci_io structure
		      is described above.  The limitations on data width de-
		      scribed for reading registers, above, also apply to
		      writing PCI configuration	registers.

     /dev/pci  Character device	for the	pci driver.


     The pci driver (not the kernel's PCI support code)	first appeared in
     FreeBSD 2.2, and was written by Stefan Esser and Garrett Wollman.	Sup-
     port for device listing and matching was re-implemented by	Kenneth	Merry,
     and first appeared	in FreeBSD 3.0.

     Kenneth Merry <>

     It	is not possible	for users to specify an	accurate offset	into the de-
     vice list without calling the PCIOCGETCONF	at least once, since they have
     no	way of knowing the current generation number otherwise.	 This probably
     is	not a serious problem, though, since users can easily narrow their
     search by specifying a pattern or patterns	for the	kernel to match

BSD			      September	30, 2007			   BSD


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