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
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.