Re: pci_intr_alloc() vs pci_intr_establish() - retry type?

[Jared McNeill <jmcneill%invisible.ca@localhost>]

On Wed, 28 Nov 2018, Mouse wrote:

> > > This reminds me - how does a driver know if any kind of MSI support
> > > is even available?
> > it shouldn't need to.
>
> Okay, then I'm missing something.  I've seen hardware where enabling
> MSI is something device-specific (a value in a register, typically),
> meaning _something_ MD, presumably the driver, has to be involved if
> MSI is to be used.
>
> And how can a driver do this without knowing whether it's supported?

The driver can call pci_intr_type on the handle returned by pci_intr_alloc 
to see what kind of interrupt (INTx/MSI/MSI-X) was negotiated.