On Wed, Sep 07, 2022 at 04:06:29PM +0200, Joerg Roedel wrote: > On Wed, Sep 07, 2022 at 10:47:39AM -0300, Jason Gunthorpe wrote: > > Would you be happier if we wrote it like > > > > #define IOMMU_EINCOMPATIBLE_DEVICE xx > > > > Which tells "which of the function parameters is actually invalid" ? > > Having done some Rust hacking in the last months, I have to say I like > to concept of error handling with Result<> there. Ideally we have a way > to emulate that in our C code without having to change all callers. 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. The unix/linux idiom is return an errno, and define what the errnos mean for your function. We have a long history of creatively applying the existing errnos, and sometimes we create new ones. We rarely return an errno and an additional error code because it doesn't fit the overall model, I can't return something like that through a system call, for instance. > What I am proposing is a way this could be emulated here, but I am open > to other suggestions. Still better than re-using random error codes for > special purposes. I think, in context of Linux as a project, it very much is worse to make up some rust-inspired error handing and discard the typical design patterns. Linux works because, for the most part, people follow similar design sensibilities throughout the tree. 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? So, again, would you be happy with a simple #define IOMMU_EINCOMPATIBLE_DEVICE xx to make it less "re-using random error codes"? Thanks, Jason
