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Re: No PCI_AUTO in 2.6...

To: wlacey <>
Subject: Re: No PCI_AUTO in 2.6...
From: Ralf Baechle <>
Date: Wed, 15 Dec 2004 14:56:56 +0100
In-reply-to: <>
Original-recipient: rfc822;
References: <>
User-agent: Mutt/1.4.1i
On Sat, Dec 11, 2004 at 01:43:05PM +0000, wlacey wrote:

> Might someone be willing to share a bit knowledge with me?
> I've transitioned to the 2.6.10 kernel and I'm having a difficult time 
> understanding what things I must do different to get my pci slots probed as 
> before in 2.4. At this point I'm well aware the 2.6 is not a drop in 
> replacement for 2.4 but what is the a general approach to getting something 
> like PCI_AUTO capability in 2.6 what steps must I take and is there document 
> describing them.

PCI_AUTO was really, really broken code.  It only works for some subset
of systems, won't handle hot plugging (Cardbus!), PCI-PCI bridges and many
other cases.  The world became a better place on the day when it got

> I call register_pci_controller() but the bus is never scanned becasue 
> pcibios_init() fails out with...
> "Skipping PCI bus scan due to resource conflict"

The new PCI code by default will fully configure a PCI bus hierarchy.  For
this to work it needs to know which memory address range and which I/O
port address range are available for assignment.  This information is
passed in the struct pci_controller argument of register_pci_controller().
Here's a simplified example from arch/mips/sni/setup.c:

static struct resource sni_io_resource = {
        "PCIMT IO MEM", 0x00001000UL, 0x03bfffffUL, IORESOURCE_IO,

static struct resource sni_mem_resource = {
        "PCIMT PCI MEM", 0x10000000UL, 0xffffffffUL, IORESOURCE_MEM

extern struct pci_ops sni_pci_ops;

static struct pci_controller sni_controller = {
        .pci_ops        = &sni_pci_ops,
        .mem_resource   = &sni_mem_resource,
        .mem_offset     = 0x10000000UL,
        .io_resource    = &sni_io_resource,
        .io_offset      = 0x00000000UL

That is PCI memory is in the address range of 0x10000000UL - 0xffffffffUL
and I/O ports in the range 0x00001000UL - 0x03bfffffUL.  The io_offset
rsp. mem_offset values say how much needs to be added rsp. subtracted
when converting a PCI bus address into a physical address.  Often these
values are either the same a the resource's start address or zero.

I hope that explains things a little ...


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