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

[ebiederm@xmission.com (Eric W. Biederman)]

Roland Dreier <rdreier@cisco.com> writes:

>  >  > - In spec hardware does not require MSI to generate interrupts
>  >  >   Which leaves enabling MSI optional.
>  > 
>  > Actually at least the Qlogic/Pathscale PCI Express ipath adapters
>  > cannot generate INTx interrupts -- they definitely do require MSI to
>  > operate.
>
> Oh yeah... when I first found out about this, I rechecked the PCI
> Express spec and found that in fact legacy INTx interrupts are
> optional.  So the ipath adapters that require MSI do conform to the
> spec.

Hmm...

I find in section 6.1:
> 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 do see it clearly stating that MSI is the preferred mechanism from
pci express.

Eric
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