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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.

     The pci driver implements the PCI bus in the kernel.  It enumerates any
     devices on the PCI bus and gives PCI client drivers the chance to attach
     to them.  It assigns resources to children, when the BIOS does not.  It
     takes care of routing interrupts when necessary.  It reprobes the unat‐
     tached PCI children when PCI client drivers are dynamically loaded at

     The pci device is included in the kernel as described in the SYNOPSIS
     section.  The pci driver cannot be built as a kld(4).

     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
				     returned by the kernel.  The items in
				     this buffer are of type pci_conf, which
				     consists 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

				     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
				     returned.	The user may pass the value
				     returned 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
				     returned 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
				     remaining 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,
				errno 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
		      described 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 ⟨ken@FreeBSD.org⟩

     It is not possible for users to specify an accurate offset into the
     device 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				January 3, 2008				   BSD

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