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SubjectRe: [PATCH 0/4] PCI legacy I/O port free driver (take4)
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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