Re: [PATCH 1/2] msi: Invert the sense of the MSI enables.

[Roland Dreier <rdreier@cisco.com>]

 > > In addition to PCI INTx compatible interrupt emulation, PCI Express
 > > requires support of MSI or MSI-X or both. 
 > Which suggests that INTx support is required.
 > 
 > I do not find any wording that suggest the opposite.
 > I do see it stated that it is intended to EOL support for INTx at
 > some point.
 > 
 > Where did you see it mentioned that INTx was optional?

I don't see any requirement that a device that generates MSI
interrupts must also be able to signal the same interrupts via INTx.
The spec explicitly says:

    "All PCI Express device Functions that are capable of generating
    interrupts must support MSI or MSI-X or both."

but there is no corresponding explicit requirement that legacy INTx
mode be supported, so it certainly seems permitted for a device not to
generate INTx interrupts.  In fact as you alluded to, the spec says,

    "The legacy INTx emulation mechanism may be deprecated in a future
    version of this specification."

and I wouldn't think the intention would be for one version of the
spec to *require* something that is planned on being deprecated later.

And the Pathscale guys were pretty confident that their device was
compliant with the PCIe spec.

 - R.