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PCI(4)                 FreeBSD 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 bus, slot and function.

                                     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 bus, slot and function.

                                     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 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 <>

     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

FreeBSD 6.2                    October 24, 1999                    FreeBSD 6.2


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