Messages in this thread | | | Date | Wed, 14 Sep 2022 10:49:42 +0100 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions |
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On Wed, Sep 14, 2022 at 06:11:06AM -0300, Jason Gunthorpe wrote: > On Tue, Sep 13, 2022 at 01:27:03PM +0100, Jean-Philippe Brucker wrote: > > I think in the future it will be too easy to forget about the constrained > > return value of attach() while modifying some other part of the driver, > > and let an external helper return EINVAL. So I'd rather not propagate ret > > from outside of viommu_domain_attach() and finalise(). > > Fortunately, if -EINVAL is wrongly returned it only creates an > inefficiency, not a functional problem. So we do not need to be > precise here.
Ah fair. In that case the attach_dev() documentation should indicate that EINVAL is a hint, so that callers don't rely on it (currently words "must" and "exclusively" indicate that returning EINVAL for anything other than device-domain incompatibility is unacceptable). The virtio-iommu implementation may well return EINVAL from the virtio stack or from the host response.
Thanks, Jean
> > > Since we can't guarantee that APIs like virtio or ida won't ever return > > EINVAL, we should set all return values: > > I dislike this alot, it squashes all return codes to try to optimize > an obscure failure path :( > > Jason
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