PCI(4) BSD Kernel Interfaces Manual PCI(4)NAMEpci — generic PCI driver
SYNOPSIS
device pciDESCRIPTION
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‐
terns.
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.
KERNEL CONFIGURATION
It is only necessary to specify one pci controller in the kernel. Addi‐
tional PCI busses are handled automatically as they are encountered.
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 sys‐
tem, 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-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 func‐
tion.
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 fol‐
lowing 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 inter‐
face.
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 off‐
set, 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 genera‐
tion 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 servic‐
ing 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 speci‐
fied by the passed-in pci_io structure. The pci_io struc‐
ture 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 ALSOpciconf(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. Sup‐
port 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.
BSD July 5, 2009 BSD
