Re: pci_enable_msi() for everyone?

[Jeff Garzik <jgarzik@pobox.com>]

Greg KH wrote:
> On Mon, Jun 06, 2005 at 07:08:33PM -0400, Jeff Garzik wrote:
>
> > Greg KH wrote:
> >
> > > Why would it matter?  The driver shouldn't care if the interrupts come
> > > in via the standard interrupt way, or through MSI, right?  And if it
> >
> > It matters.
> >
> > Not only the differences DaveM mentioned, but also simply that you may 
> > assume your interrupt is not shared with anyone else.
>
>
> Ok, and again, how would the call, pci_in_msi_mode(struct pci_dev *dev)
> not allow for the driver to determine this?

Let me see if I understand this correctly :)

A technology (MSI) allows one to more efficiently call interrupt 
handlers, with fewer bus reads...  and you want to add a test to each 
interrupt handler -- a test which adds several bus reads to the hot path 
of every MSI driver?

We want to -decrease- the overhead involved with an interrupt, but 
pci_in_msi_mode() increases it.

	Jeff


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