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However, this >> becomes annoying when the corresponding device is u32 (or even smaller outside >> of DRM). Because then we have all the fallible conversions on the other end >> where the driver interacts with the HW. >> >> So, on the Rust side I think we want to abstract this, such that drivers can >> choose the actual device size type and the corresponding APIs just work with >> this type and store the actual value in the backing u64 internally, but hand it >> out as the actual type the driver passed in originally. > > I see, thanks for that context -- yes, if the types are different and > known, it would be better to abstract over the right one. > > (And perhaps it may even make sense to use newtypes too, depending on > the details.) It might. Because GpuAddr is a bit vague, whereas FbAddr is always going to be u64. OK, I think a define_size!() macro that implements a DeviceSize trait works here. We still end up converting call sites to use sizes::u64::SZ_1M, once DeviceSize is in scope. And then later, one can build on top of that with things such as , and such. I'll post a v2, assuming that this sounds about right. thanks, -- John Hubbard