Messages in this thread | | | From | David Brownell <> | Subject | Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set | Date | Sun, 15 Oct 2006 15:45:58 -0700 |
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> > Most drivers should be able to say "enable MWI if possible, but > > don't worry if it's not possible". Only a few controllers need > > additional setup to make MWI actually work ... if they couldn't > > do that setup, that'd be worth a warning before they backed off > > to run in a non-MWI mode. > > > > So the semantics of pci_set_mwi() are "try to set MWI if this > platform/device supports it".
Not what I said ... that's what the _driver_ usually wants to do, which is different from the step implemented by set_mwi().
What Alan Cox said is a better paraphrase:
> MWI is an "extra cheese" option not a "no pizza" case
Or "sorry, that car is not available in olive, just burgundy."
Not:
> In that case its interface is misdesigned, because it doesn't discriminate > between "yes-it-does/no-it-doesn't" (which we don't want to report, because > either is expected and legitimate) and "something screwed up", which we do > want to report, because it is always unexpected.
You mis-understand. It's completely legit for the driver not to care.
I agree that set_mwo() should set MWI if possible, and fail cleanly if it couldn't (for whatever reason). Thing is, choosing to treat that as an error must be the _driver's_ choice ... it'd be wrong to force that policy into the _interface_ by forcing must_check etc.
- Dave
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