Subject: Re: [PATCH 3/4] Simplify rtas_change_msi() error semantics

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 02 Oct 2007 16:24:13 +1000

On Tue, 2007-10-02 at 15:58 +1000, Michael Ellerman wrote:
> > Looks allright, just a question tho... what do we do if it fails ?
> Do we
> > try to fallback to a lower number of MSIs ? Or what ? Dead device ?
> 
> That's all up to the device driver. In theory the driver could try again
> with a lower count - but that might require extra logic in the driver to
> handle shared irq handlers etc. In practice I think the current drivers
> will just fail.

Question is badly phrased.. I meant something more like... what do we do
if RTAS returns a lower count ?

That is, we end up with that device with that lower count of MSIs
enabled, we fail at the driver level, do we still somewhat keep track ?
Drivers might assume that means it can use LSIs no ? which may not be
the case... Shouldn't we try to switch back to LSI mode (or does the
RTAS interface doesnt allow it ?)

Ben.