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

Greg KH
2005-06-07T05:16:07Z

On Mon, Jun 06, 2005 at 06:09:11PM -0700, Andrew Vasquez wrote:
> On Mon, 06 Jun 2005, Greg KH wrote:
>
> >
> > Ok, as it seems there is a bit of confusion, here's real code that
> > should help explain what I am proposing. This works on my desktop, but
> > I don't think it supports MSI :)
> >
> > I'll go dig out an old 4-way AMD box that has MSI to see if this still
> > works properly, but comments are welcome.
>
>
> Thanks for posting some sample code. Some comments though:
>
> * 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.

> * A device (notably, our 4gb PCIe fibre-channel products) can support
> both MSI and MSI-X. Since the driver has no way of 'disabling' MSI,
> how would it enable MSI-X?

Agreed, let me respin the patches again, because I think I got the logic
wrong on some of these drivers because of this...

thanks,

greg k-h