freebsd-dev/share/man/man4/pci.4

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.Dd January 3, 2008
.Dt PCI 4
.Os
.Sh NAME
.Nm pci
.Nd generic PCI driver
.Sh SYNOPSIS
.Cd device pci
.Sh DESCRIPTION
The
.Nm
driver provides a way for userland programs to read and write
.Tn PCI
configuration registers.
It also provides a way for userland programs to get a list of all
.Tn PCI
devices, or all
.Tn PCI
devices that match various patterns.
.Pp
Since the
.Nm
driver provides a write interface for
.Tn PCI
configuration registers, system administrators should exercise caution when
granting access to the
.Nm
device.
If used improperly, this driver can allow userland applications to
crash a machine or cause data loss.
.Pp
The 
.Nm 
driver implements the
.Tn PCI
bus in the kernel.
It enumerates any devices on the
.Tn PCI
bus and gives
.Tn 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
.Tn PCI
children when
.Tn PCI
client drivers are dynamically
loaded at runtime.
.Sh KERNEL CONFIGURATION
The 
.Nm
device is included in the kernel as described in the SYNOPSIS section.
The
.Nm
driver cannot be built as a
.Xr kld 4 .
.Sh IOCTLS
The following
.Xr ioctl 2
calls are supported by the
.Nm
driver.
They are defined in the header file
.In sys/pciio.h .
.Bl -tag -width 012345678901234
.Pp
.It PCIOCGETCONF
This
.Xr ioctl 2
takes a
.Va pci_conf_io
structure.
It allows the user to retrieve information on all
.Tn PCI
devices in the system, or on
.Tn PCI
devices matching patterns supplied by the user.
The call may set
.Va errno
to any value specified in either
.Xr copyin 9
or
.Xr copyout 9 .
The
.Va pci_conf_io
structure consists of a number of fields:
.Bl -tag -width match_buf_len
.It pat_buf_len
The length, in bytes, of the buffer filled with user-supplied patterns.
.It num_patterns
The number of user-supplied patterns.
.It patterns
Pointer to a buffer filled with user-supplied patterns.
.Va patterns
is a pointer to
.Va num_patterns
.Va pci_match_conf
structures.
The
.Va pci_match_conf
structure consists of the following elements:
.Bl -tag -width pd_vendor
.It pc_sel
.Tn PCI
domain, bus, slot and function.
.It pd_name
.Tn PCI
device driver name.
.It pd_unit
.Tn PCI
device driver unit number.
.It pc_vendor
.Tn PCI
vendor ID.
.It pc_device
.Tn PCI
device ID.
.It pc_class
.Tn PCI
device class.
.It 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
.Va pci_getconf_flags
structure.
Hopefully the flag values are obvious enough that they do not need to
described in detail.
.El
.It match_buf_len
Length of the
.Va matches
buffer allocated by the user to hold the results of the
.Dv PCIOCGETCONF
query.
.It num_matches
Number of matches returned by the kernel.
.It matches
Buffer containing matching devices returned by the kernel.
The items in this buffer are of type
.Va pci_conf ,
which consists of the following items:
.Bl -tag -width pc_subvendor
.It pc_sel
.Tn PCI
domain, bus, slot and function.
.It pc_hdr
.Tn PCI
header type.
.It pc_subvendor
.Tn PCI
subvendor ID.
.It pc_subdevice
.Tn PCI
subdevice ID.
.It pc_vendor
.Tn PCI
vendor ID.
.It pc_device
.Tn PCI
device ID.
.It pc_class
.Tn PCI
device class.
.It pc_subclass
.Tn PCI
device subclass.
.It pc_progif
.Tn PCI
device programming interface.
.It pc_revid
.Tn PCI
revision ID.
.It pd_name
Driver name.
.It pd_unit
Driver unit number.
.El
.It 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
.Dv PCIOCGETCONF
ioctl.
If the user does not intend to use the offset, it must be set to zero.
.It generation
.Tn 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
.Dv PCIOCGETCONF
ioctl.
If the device list has changed, a status of
.Va PCI_GETCONF_LIST_CHANGED
will be passed back.
.It status
The status tells the user the disposition of his request for a device list.
The possible status values are:
.Bl -ohang
.It PCI_GETCONF_LAST_DEVICE
This means that there are no more devices in the PCI device list after the
ones returned in the
.Va matches
buffer.
.It PCI_GETCONF_LIST_CHANGED
This status tells the user that the
.Tn PCI
device list has changed since his last call to the
.Dv PCIOCGETCONF
ioctl and he must reset the
.Va offset
and
.Va generation
to zero to start over at the beginning of the list.
.It 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.
.It PCI_GETCONF_ERROR
This indicates a general error while servicing the user's request.
If the
.Va pat_buf_len
is not equal to
.Va num_patterns
times
.Fn sizeof "struct pci_match_conf" ,
.Va errno
will be set to
.Er EINVAL .
.El
.El
.It PCIOCREAD
This
.Xr ioctl 2
reads the
.Tn PCI
configuration registers specified by the passed-in
.Va pci_io
structure.
The
.Va pci_io
structure consists of the following fields:
.Bl -tag -width pi_width
.It pi_sel
A
.Va 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.
.It pi_reg
The
.Tn PCI
configuration register the user would like to access.
.It 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.
.It pi_data
The data returned by the kernel.
.El
.It PCIOCWRITE
This
.Xr ioctl 2
allows users to write to the
.Tn PCI
specified in the passed-in
.Va pci_io
structure.
The
.Va pci_io
structure is described above.
The limitations on data width described for
reading registers, above, also apply to writing
.Tn PCI
configuration registers.
.El
.Sh FILES
.Bl -tag -width /dev/pci -compact
.It Pa /dev/pci
Character device for the
.Nm
driver.
.El
.Sh SEE ALSO
.Xr pciconf 8
.Sh HISTORY
The
.Nm
driver (not the kernel's
.Tn PCI
support code) first appeared in
.Fx 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
.Fx 3.0 .
.Sh AUTHORS
.An Kenneth Merry Aq ken@FreeBSD.org
.Sh BUGS
It is not possible for users to specify an accurate offset into the device
list without calling the
.Dv 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.