Broadcom_bus.c was added in 2.6.35 to support PCI hotplug on a couple old
boards that don't have ACPI at all.
There are three categories of machines with CNB20LE:
1) Those without ACPI at all
2) Pre-2008 machines with ACPI, where the host bridges should be
described in ACPI, but Linux doesn't look at _CRS
3) 2008 and newer machines with ACPI, where Linux uses _CRS
Broadcom_bus.c was intended for category 1. I think this includes very few
machines, and even fewer where we care about PCI hotplug.
But it's currently also used for category 2, which includes many more
machines, and it changes the behavior from "assume everything in the PCI
gap is routed to bus 0" to "figure out the windows using broadcom_bus.c."
This broke a Compaq ProLiant DL320 because broadcom_bus.c is incomplete
(since there are no public specs), and the windows it discovers don't
mesh with the working device configuration from BIOS, so Linux moves
devices around and breaks things. See:
https://bugzilla.redhat.com/show_bug.cgi?id=665109
These two patches limit the use of broadcom_bus.c to category 1 and
discourage its use at all in general-purpose kernels, because I doubt
distros care about supporting PCI hotplug on those machines.
Bjorn
---
Bjorn Helgaas (2):
x86/PCI: don't use native Broadcom CNB20LE driver when ACPI is available
x86/PCI: make Broadcom CNB20LE driver EMBEDDED and EXPERIMENTAL
arch/x86/Kconfig | 10 ++++++++--
arch/x86/pci/broadcom_bus.c | 11 +++++++----
2 files changed, 15 insertions(+), 6 deletions(-)
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