On Wed, Sep 07, 2022 at 02:10:33PM -0300, Jason Gunthorpe wrote: > Sure, rust has all sorts of nice things. But the kernel doesn't follow > rust idioms, and I don't think this is a great place to start > experimenting with them. It is actually a great place to start experimenting. The IOMMU interfaces are rather domain specific and if we get something wrong the damage is limited to a few callers. There are APIs much more exposed in the kernel which would be worse for that. But anyway, I am not insisting on it. > It has been 3 months since EMEDIUMTYPE was first proposed and 6 > iterations of the series, don't you think it is a bit late in the game > to try to experiment with rust error handling idioms? If I am not mistaken, I am the person who gets blamed when crappy IOMMU code is sent upstream. So it is also up to me to decide in which state and how close to merging a given patch series is an whether it is already 'late in the game'. > So, again, would you be happy with a simple > > #define IOMMU_EINCOMPATIBLE_DEVICE xx > > to make it less "re-using random error codes"? I am wondering if this can be solved by better defining what the return codes mean and adjust the call-back functions to match the definition. Something like: -ENODEV : Device not mapped my an IOMMU -EBUSY : Device attached and domain can not be changed -EINVAL : Device and domain are incompatible ... That would be much more intuitive than using something obscure like EMEDIUMTYPE. Regards, Joerg
