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SubjectRe: [PATCH 0/6] PCI legacy I/O port free driver (take2)
Benjamin Herrenschmidt wrote:
>>Here, there are many PCI devices that provide both I/O port and MMIO
>>interface, and some of those devices can be handled without using I/O
>>port interface. The reason why such devices provide I/O port interface
>>is for compatibility to legacy OSs. So this kind of devices should
>>work even if enough I/O port resources are not assigned. The "PCI
>>Local Bus Specification Revision 3.0" also mentions about this topic
>>(Please see p.44, "IMPLEMENTATION NOTE"). On the current linux,
>>unfortunately, this kind of devices don't work if I/O port resources
>>are not assigned, because pci_enable_device() for those devices fails.
>
>
> Which is where the real problem is ... I'm afraid you are doing a
> workaround for the wrong issue... do we really need to assign all
> resources to the device at pci_enable_device() time ? Yeah, I know, that
> sounds gross... but think about it... doesn't pci_request_region(s) look
> like a better spot ? Or maybe we should change pci_enable_device()
> itself to take a mask of BARs that are relevant. That would help dealing
> with a couple of other cases of devices where some BARs really need to
> be ignored...
>
> The later is probably the best approach without breaking everything, by
> having a new pci_enable_resources(mask) that would take a mask of BARs
> to enable, with pci_enable_device() becoming just a call to the former
> for all BARs ....
>
> Ben.
>

I guess the existing pci_enable_device_bars() is very similar to
your pci_enable_resources(). We already discussed it at:

http://marc.theaimsgroup.com/?l=linux-kernel&m=114000705026791&w=2

Thanks,
Kenji Kaneshige
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