Re: [RFC][PATCH] Add PCI<->PCI bridge driver [4/9]

From: Adam Belay (abelay_at_novell.com)
Date: 07/16/05

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    To: Russell King <rmk+lkml@arm.linux.org.uk>
Date:	Fri, 15 Jul 2005 23:10:52 -0400

    On Fri, 2005-07-15 at 09:58 +0100, Russell King wrote:
    > On Thu, Jul 14, 2005 at 04:55:19AM -0400, Adam Belay wrote:
    > > This patch adds a basic PCI<->PCI bridge driver that utilizes the new
    > > PCI bus class API.
    >
    > Thanks. I think this breaks Cardbus.
    >
    > The whole point of the way PCI is _presently_ organised is that it allows
    > busses to be configured and setup _before_ the devices are made available
    > to drivers. This breaks that completely:

    Hi Russell,

    I'm aware of this issue. These changes are major and will need more
    than one pass to be correct. I'll be redoing most of the bus
    configuration code in the next patch set. I have a strategy for proper
    device and bus configuration. These are my current thoughts:

    1.) When bound to its device PCI bridge drivers will add their current
    devices to the bus device list, but will not register them with the
    driver model.

    2.) The bus class driver will initiate a procedure similar to
    pci_bus_add_devices(), but only for host (root) bridges and hot-plugged
    devices.

    pci_register_bus_devices(struct pci_bus *bus)
    {
    - register all bios configured bridges
    - call pci_register_bus_devices() for each previously registered bridge
    - register remaining uninitialized bridges and call
    pci_register_bus_devices() for each bridge as it's registered.
    }

    pci_register_devices(struct pci_bus *bus)
    {
    - register all remaining PCI devices, including those of child pci buses
    }

    * pci_register_bus_devices() will be called first followed by
    pci_register_devices().

    3.) Bridge windows will not be configured until a child device is
    enabled. In other words, resource configuration is lazy much like we
    handle PCI IRQ routing. We will, however, verify the validity of BIOS
    assignments. If the assignments are incorrect, the bridge will be
    disabled and then reconfigured when needed.

    Thanks,
    Adam

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