pcibios - introduction to PCI BIOS support
pcibios0 at bios0 flags 0x0000
OpenBSD provides support for setting up PCI controllers,
bridges, and devices
using information extracted from the BIOS.
Ideally, the boot firmware of a machine (a.k.a. BIOS) should
set up all
PCI devices; assigning them I/O and memory addresses and interrupts.
Alas, this does not always happen, so there is some PC specific code that
can do the initialization when OpenBSD boots.
Flags is a bit mask each bit of which specifies a fixup procedure to
omit. The following list specifies these procedures and
gives flags bit
values to disable them in case they cause problems.
0x0001 Fixup PCI I/O and memory addresses.
Some BIOS implementations don't allocate I/O space
space for all PCI devices. Especially, a BIOS which
has "PnP OS
mode" enabled shows this behavior. Since necessary
allocated, those devices will not work without special handling.
Without this flag force allocation of I/O space and
instead of relying upon the BIOS to do so.
If necessary space is already correctly assigned to
this option leaves the space as is.
Although many BIOS implementations leave CardBus
unallocated, the CardBus bridge device driver
this option, since the driver allocates necessary
space by itself.
0x0002 Fixup PCI bus numbering; needed for many cardbus(4)
Each PCI bus and CardBus should have a unique bus
some BIOS implementations don't assign a bus number
PCI buses. And many BIOS implementations don't
assign a bus
number for CardBuses.
A typical symptom of this is the following boot message:
cardbus0 at cardslot0: bus 0 device 0...
Please note that this cardbus0 has a bus number `0',
the bus number 0 is used by the machine's primary
PCI bus. Thus,
this bus number for cardbus is incorrect (not assigned). In this
situation, a device located in cardbus0 doesn't show
ID, because its bus number 0 incorrectly refers
to the primary
PCI bus, and a device ID in the primary PCI bus
is shown in
the boot message instead of the device's ID in the
Without this flag force assignment of bus numbers
for all subordinate
PCI buses and CardBuses.
Since this procedure renumbers all PCI buses and
bus numbers of subordinate buses become different
when this option
0x0004 Fixup PCI interrupt routing.
Some BIOS implementations don't assign an interrupt
for some devices.
This procedure assigns an interrupt for such devices
relying upon the BIOS to do so.
If the BIOS has already assigned an interrupt to a
procedure leaves the interrupt as is.
0x0008 Make PCI interrupt routing fixup work with unknown
routers. If this flag is specified and a PCI interrupt routing
table entry indicates that only one IRQ is available
for the entry,
the IRQ is assumed to be already connected to
and the corresponding PCI Interrupt Configuration
be configured accordingly.
Without this flag, if a PCI interrupt router is not
configuration will not be modified.
0x0010 Be verbose when performing pcibios tasks. Included
in these diagnostics
are: PCI device address fixup tables, interrupt fixup
reports, and other diagnostic and non-fatal messages.
0x0020 Make the PCI interrupt routing fixup procedure verbose.
bios(4), intro(4), pci(4)
The pcibios code appeared in NetBSD 1.5. OpenBSD support
was added in
OpenBSD 2.8. In contrast to NetBSD implementation pcibios
in OpenBSD is
a real device, where options control is done through the
flags which are
modifiable through the boot_config(8) interface. For OpenBSD 2.9 the PCI
interrupt routing establishment sequence was redone to only
route interrupts when attaching interrupts for a particular
The PCIBIOS Address Fixup option may conflict with the PCI
own address fixup.
OpenBSD 3.6 July 22, 2000
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