Ubuntu Manpage: pci — generic PCI bus driver

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NAME

     pci — generic PCI bus driver

SYNOPSIS

     To compile the PCI bus driver into the kernel, place the following line in your kernel
     configuration file:

           device pci

     To compile in support for Single Root I/O Virtualization (SR-IOV):

           options PCI_IOV

     To compile in support for native PCI-express HotPlug:

           options PCI_HP

DESCRIPTION

     The pci driver provides support for PCI devices in the kernel and limited access to PCI
     devices for userland.

     The pci driver provides a /dev/pci character device that can be used by userland programs to
     read and write PCI configuration registers.  Programs can also use this device 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.  The pci driver also includes support for PCI-PCI bridges, various platform-
     specific Host-PCI bridges, and basic support for PCI VGA adapters.

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 matching the specified criteria 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
match his 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.

LOADER TUNABLES

Tunables can be set at the loader(8) prompt before booting the kernel, or stored in
loader.conf(5). The current value of these tunables can be examined at runtime via
sysctl(8) nodes of the same name. Unless otherwise specified, each of these tunables is a
boolean that can be enabled by setting the tunable to a non-zero value.

hw.pci.clear_bars (Defaults to 0)
Ignore any firmware-assigned memory and I/O port resources. This forces the PCI bus
driver to allocate resource ranges for memory and I/O port resources from scratch.

hw.pci.clear_buses (Defaults to 0)
Ignore any firmware-assigned bus number registers in PCI-PCI bridges. This forces
the PCI bus driver and PCI-PCI bridge driver to allocate bus numbers for secondary
buses behind PCI-PCI bridges.

hw.pci.clear_pcib (Defaults to 0)
Ignore any firmware-assigned memory and I/O port resource windows in PCI-PCI
bridges. This forces the PCI-PCI bridge driver to allocate memory and I/O port
resources for resource windows from scratch.

By default the PCI-PCI bridge driver will allocate windows that contain the
firmware-assigned resources devices behind the bridge. In addition, the PCI-PCI
bridge driver will suballocate from existing window regions when possible to satisfy
a resource request. As a result, both hw.pci.clear_bars and hw.pci.clear_pcib must
be enabled to fully ignore firmware-supplied resource assignments.

hw.pci.default_vgapci_unit (Defaults to -1)
By default, the first PCI VGA adapter encountered by the system is assumed to be the
boot display device. This tunable can be set to choose a specific VGA adapter by
specifying the unit number of the associated vgapciX device.

hw.pci.do_power_nodriver (Defaults to 0)
Place devices into a low power state (D3) when a suitable device driver is not
found. Can be set to one of the following values:

3 Powers down all PCI devices without a device driver.

2 Powers down most devices without a device driver. PCI devices with the
display, memory, and base peripheral device classes are not powered down.

1 Similar to a setting of 2 except that storage controllers are also not
powered down.

0 All devices are left fully powered.

A PCI device must support power management to be powered down. Placing a device
into a low power state may not reduce power consumption.

hw.pci.do_power_resume (Defaults to 1)
Place PCI devices into the fully powered state when resuming either the system or an
individual device. Setting this to zero is discouraged as the system will not
attempt to power up non-powered PCI devices after a suspend.

hw.pci.do_power_suspend (Defaults to 1)
Place PCI devices into a low power state when suspending either the system or
individual devices. Normally the D3 state is used as the low power state, but
firmware may override the desired power state during a system suspend.

hw.pci.enable_ari (Defaults to 1)
Enable support for PCI-express Alternative RID Interpretation. This is often used
in conjunction with SR-IOV.

hw.pci.enable_io_modes (Defaults to 1)
Enable memory or I/O port decoding in a PCI device's command register if it has
firmware-assigned memory or I/O port resources. The firmware (BIOS) in some systems
does not enable memory or I/O port decoding for some devices even when it has
assigned resources to the device. This enables decoding for such resources during
bus probe.

hw.pci.enable_msi (Defaults to 1)
Enable support for Message Signalled Interrupts (MSI). MSI interrupts can be
disabled by setting this tunable to 0.

hw.pci.enable_msix (Defaults to 1)
Enable support for extended Message Signalled Interrupts (MSI-X). MSI-X interrupts
can be disabled by setting this tunable to 0.

hw.pci.enable_pcie_hp (Defaults to 1)
Enable support for native PCI-express HotPlug.

hw.pci.honor_msi_blacklist (Defaults to 1)
MSI and MSI-X interrupts are disabled for certain chipsets known to have broken MSI
and MSI-X implementations when this tunable is set. It can be set to zero to permit
use of MSI and MSI-X interrupts if the chipset match is a false positive.

hw.pci.iov_max_config (Defaults to 1MB)
The maximum amount of memory permitted for the configuration parameters used when
creating Virtual Functions via SR-IOV. This tunable can also be changed at runtime
via sysctl(8).

hw.pci.realloc_bars (Defaults to 0)
Attempt to allocate a new resource range during the initial device scan for any
memory or I/O port resources with firmware-assigned ranges that conflict with
another active resource.

hw.pci.usb_early_takeover (Defaults to 1 on amd64 and i386)
Disable legacy device emulation of USB devices during the initial device scan. Set
this tunable to zero to use USB devices via legacy emulation when using a custom
kernel without USB controller drivers.

hw.pci<D>.<B>.<S>.INT<P>.irq
These tunables can be used to override the interrupt routing for legacy PCI INTx
interrupts. Unlike other tunables in this list, these do not have corresponding
sysctl nodes. The tunable name includes the address of the PCI device as well as
the pin of the desired INTx IRQ to override:

<D> The domain (or segment) of the PCI device in decimal.

<B> The bus address of the PCI device in decimal.

<S> The slot of the PCI device in decimal.

<P> The interrupt pin of the PCI slot to override. One of ‘A’, ‘B’, ‘C’, or
‘D’.

The value of the tunable is the raw IRQ value to use for the INTx interrupt pin
identified by the tunable name. Mapping of IRQ values to platform interrupt sources
is machine dependent.

FILES

     /dev/pci  Character device for the pci driver.

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.