[Patch Part2 v4 21/31] PCI/MSI: enhance PCI MSI core to support hierarchy irqdomain

[Bjorn Helgaas]

On Wed, Nov 5, 2014 at 6:58 PM, Yijing Wang <wangyijing at huawei.com> wrote:

>>> +{
>>> +    return (irq_hw_number_t)msidesc->msi_attrib.entry_nr |
>>> +            PCI_DEVID(pdev->bus->number, pdev->devfn) << 11 |
>>> +            (pci_domain_nr(pdev->bus) & 0xFFFFFFFF) << 27;
>>
>> Where does this bit layout come from?  Is this defined in the spec
>> somewhere?  A reference would help.
>
> Currently, more and more Non-PCI device use MSI(or similar MSI mechanism), like DMAR fault irq
> and HPET FSB irq. And we have to add additional code to support the MSI capability.
> So I hope we can decouple MSI code and PCI code, then we can unify all MSI(or Message Based interrupt)
> in one framework.

Was that supposed to answer my question?  If so, I didn't understand
how it explains where the bit layout came from.

Bjorn