Do not probe for the PCI bus.

Force the use of the PCI BIOS by not accessing the hardware directly. This means that the kernel should trust the BIOS, which is not the standard thing to do (as BIOSes are known to lie more than they are known to be valid.) Use this only if your machine has a non-standard PCI host bridge and the normal boot method is not working properly.

Do not use the PCI BIOS, but access the hardware directly instead. This is the default method of probing for PCI devices in all kernels after 2.6.13.

Force use of PCI Configuration Mechanism 1 (a way to access PCI memory on i386 machines.)

Force use of PCI Configuration Mechanism 2 (a way to access PCI memory on i386 machines.)

Disable use of the ACPI MMCONFIG table for PCI configuration.

If the PCI_MSI kernel config parameter is enabled, this kernel boot option can be used to disable the use of MSI interrupts system-wide.

Do not sort PCI devices according to order given by the PCI BIOS. This sorting is done to get a device order compatible with much older kernel versions.

Use PCI BIOS calls to get the interrupt routing table. These calls are known to be buggy on several machines and hang these machine when used, but on other machines they are the only way to get the interrupt routing table. Try this option if the kernel is unable to allocate IRQs or discover secondary PCI buses on your motherboard.

Assign address space to expansion ROMs. Use this with caution as certain devices share address decoders between ROMs and other resources.

Set a bit mask of IRQs allowed to be assigned automatically to PCI devices. You can make the kernel exclude IRQs of your ISA cards this way.

Specify the physical address of the PIRQ table (normally generated by the BIOS) if it is outside the F0000-100000 (hexadecimal) range.

Scan all buses through bus n . Can be useful if the kernel is unable to find your secondary buses and you want to tell it explicitly which ones they are.

Always use your own PCI bus numbers, overriding whatever the firmware may have done.

Honor the possible IRQ mask stored in the BIOS $PIR table. This is needed on some systems with broken BIOSes, notably some HP Pavilion N5400 and Omnibook XE3 notebooks. This will have no effect if ACPI IRQ routing is enabled.

Do not use ACPI for IRQ routing or for PCI scanning.

Do IRQ routing for all PCI devices. This is normally done in pci_enable_device(), so this option is a temporary workaround for broken drivers that don't call it.

Do not re-enumerate the bus, but instead just use the configuration from the bootloader. This is currently used on IXP2000 systems where the bus has to be configured a certain way for adjunct CPUs.