Re: MSI and driver APIs

[David S. Miller]

From: Roland Dreier <rdreier@xxxxxxxxx>
Date: Thu, 15 Dec 2005 13:18:04 -0800

>     Benjamin> I'm tempted to leave them enabled and only disable them
>     Benjamin> when request_irq() is done on the legacy INTx... Does
>     Benjamin> anybody see a problem with this approach ?
> 
> You might run into trouble on hardware (think tg3 or its ilk again)
> where you might have to do something beyond disabling MSI in the PCI
> header to switch the chip out of MSI mode.

I think because of kinds of cases and other issues, going with
MSI by default is a non-starter.

Perhaps a better approach is to use a flag in the pci_driver_struct or
similar that says "you can have MSI enabled by default".  And
gradually convert drivers over which we know will handle it properly.

Doing some tom foolery with request_irq() sounds like a half-baked
idea at best.  The biggest argument against that is that this is
not a PCI interface, so expecting it to have PCI side effects is
really asking for trouble.
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