Provided by: freebsd-manpages_10.1~RC1-1_all 
NAME
pci — generic PCI driver
SYNOPSIS
device pci
DESCRIPTION
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 patterns.
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 unattached PCI children when PCI client drivers are dynamically loaded at
runtime.
KERNEL CONFIGURATION
The pci device is included in the kernel as described in the SYNOPSIS section. The pci
driver cannot be built as a kld(4).
IOCTLS
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 specified 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-supplied 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 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 structure. Hopefully the flag
values 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 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 interface.
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 back.
status The status tells the user the disposition of his request for
a device list. The possible status values are:
PCI_GETCONF_LAST_DEVICE
This means that there are no more devices in the PCI device
list after the ones returned in the matches buffer.
PCI_GETCONF_LIST_CHANGED
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.
PCI_GETCONF_MORE_DEVS
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 possible for this status
to be returned, even when none of the remaining devices in
the list would match the user's criteria.
PCI_GETCONF_ERROR
This indicates a general error while servicing 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.
FILES
/dev/pci Character device for the pci driver.
SEE ALSO
pciconf(8)
HISTORY
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. Support for device listing and matching was
re-implemented by Kenneth Merry, and first appeared in FreeBSD 3.0.
AUTHORS
Kenneth Merry <ken@FreeBSD.org>
BUGS
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
against.