Re: [RFC PATCH] PCI: remove access to pci_[enable|disable]_msi() for drivers

Grant Grundler
2005-06-07T16:04:56Z

On Tue, Jun 07, 2005 at 09:31:39AM +0200, Arjan van de Ven wrote:
>
> > > * What if the driver writer does not want MSI enabled for their
> > > hardware (even though there is an MSI capabilities entry)? Reasons
> > > include: overhead involved in initiating the MSI; no support in some
> > > versions of firmware (QLogic hardware).
> >
> > Yes, a very good point. I guess I should keep the pci_enable_msi() and
> > pci_disable_msi() functions exported for this reason.
> >
>
> well... only pci_disable_msi() is needed for this ;)

It depends on how the switch from MSI to MSI-X is supposed to work.
I'm thinking of the following sort of sequence:
pci_disable_msi(dev);
if (pci_enable_msix(dev,...)) {
register MSIX stuff
} else {
/* MSIX won't work...fall back to MSI */
pci_enable_msi(dev);
}

and that makes a bad assumption MSI will work.

grant