On 9/8/25 12:02, Manos Pitsidianakis wrote:
Hi Paolo,
I'm not familiar with how migration works under the hood, but this
data transformation design looks very clean and neat to me.
Thanks!
Using it is very easy, you can just declare your state like:
regs: Migratable<Mutex<MyDeviceRegisters>>
Hm it's a shame we cannot do this with a trait since it requires state
storage for migration_state.
Yeah, but a Box is just a single pointer. We need to have an actual
location in memory for the C code to retrieve the pointer.
A suggestion: we could declare a "mirror" struct to hold
`migration_state` with a Derive macro. This is what the `rkyv` crate
does with its `Archive` derive macro and trait
<https://docs.rs/rkyv/latest/rkyv/trait.Archive.html>
Nice! I'm not familiar with rkyv but it does look very similar.
When I tried to clean up the HPET (create HPETRegisters, and replace use
of raw pointers with self_cell to implement self-referential structs),
migration was the big mess, so I hope that this design will fix both
that and Mutex<>. And indeed having a derive macro is very similar to
what I came up with one day later :) while thinking about how HPET could
use it in practice.
Probably the derive macro would require some changes to the trait, but
the basic idea remains the same.
Paolo
