Messages in this thread | | | Date | Mon, 16 Oct 2006 10:44:30 +1000 | From | Paul Mackerras <> | Subject | Re: [PATCH 1/2] [PCI] Check that MWI bit really did get set |
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Andrew Morton writes:
> Let me restore the words from my earlier email which you removed so that > you could say that: > > For you the driver author to make assumptions about what's happening > inside pci_set_mwi() is a layering violation. Maybe the bridge got > hot-unplugged. Maybe the attempt to set MWI caused some synchronous PCI > error. For example, take a look at the various implementations of > pci_ops.read() around the place - various of them can fail for various > reasons.
Maybe aliens are firing a ray-gun at the card. I think it's fundamentally wrong for the driver to deny service completely because of a maybe.
Either there was a transient error that only affected the attempt to set MWI, in which case a printk (inside pci_set_mwi!) is appropriate, and we carry on. Or there is a persistent error condition, in which case the driver will see something else fail soon enough - something that the driver actually needs to have working in order to operate - and fail at that point.
For the driver to stop and refuse to go any further because of an error in pci_set_mwi has far more disadvantages than advantages.
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