Messages in this thread | | | Date | Sat, 10 Sep 2005 17:07:04 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [GIT PATCH] More PCI patches for 2.6.13 |
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On Fri, 9 Sep 2005, Linus Torvalds wrote: > > On Fri, 9 Sep 2005, Linus Torvalds wrote: > > > > There are functions where it is really _important_ to check the error > > return, because they return errors often enough - and the error case is > > something you have to do something about - that it's good to force people > > to be aware. > > > > But "pci_set_power_state()"? > > > > I don't think so. > > Btw, a perfect example of this is > > pci_set_power_state(pdev, 0); > > which is a very common thing to do in a driver init routine. And it has > absolutely _no_ valid return values: it either succeeds, or it doesn't, > and the only reason it wouldn't succeed is because the device doesn't > support power management in the first place (in which case it already > effectively is in state 0). > > In other words, there's nothing you can or should do about it. Testing the > return value is pointless. And thus adding a "must_check" is really really > wrong: it might make people do > > if (pci_set_power_state(pdev, 0)) > return -ENODEV > > which is actually actively the _wrong_ thing to do, and would just cause > old revisions of the chip that might not support PM capabilities to no > longer work.
Funny you should say this -- exactly that problem _did_ arise. See
http://marc.theaimsgroup.com/?l=linux-pci&m=112621842604724&w=2
pci_enable_device_bars() would an error when trying to initialize devices without PM support, because it started checking the return value from pci_set_power_state().
Alan Stern
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