Messages in this thread | | | Date | Thu, 02 Mar 2006 13:12:35 -0500 | From | Jeff Garzik <> | Subject | Re: [PATCH 0/4] PCI legacy I/O port free driver (take4) |
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Russell King wrote: > It's not really "I/O port resource allocation" though - the resources > have already been allocated and potentially programmed into the BARs > well before the driver gets anywhere near the device. [...] > Are you implying that somehow resources are allocated at pci_enable_device > time? If so, shouldn't we be thinking of moving completely to that model > rather than having yet-another-pci-setup-model.
Actually, that's has been the rule ever since the cardbus days: resources -- bars and irqs -- should not be considered allocated until after pci_enable_device().
Documentation/pci.txt reflects this reality as well:
> 3. Enabling and disabling devices > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > Before you do anything with the device you've found, you need to enable > it by calling pci_enable_device() which enables I/O and memory regions of > the device, allocates an IRQ if necessary, assigns missing resources if > needed and wakes up the device if it was in suspended state. Please note > that this function can fail.
Any PCI driver that presumes -anything- about resources before calling pci_enable_device() is buggy, and that's been the case for many years. Some platform-specific PCI drivers violate this with special knowledge, but overall that's the rule.
Regards,
Jeff
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