On Wed May 6, 2026 at 1:42 PM BST, Alice Ryhl wrote: > On Tue, May 05, 2026 at 05:23:08PM +0200, Danilo Krummrich wrote: >> Add a registration_data pointer to struct auxiliary_device, allowing the >> registering (parent) driver to attach private data to the device at >> registration time and retrieve it later when called back by the >> auxiliary (child) driver. >> >> By tying the data to the device's registration, Rust drivers can bind >> the lifetime of device resources to it, since the auxiliary bus >> guarantees that the parent driver remains bound while the auxiliary >> device is bound. >> >> On the Rust side, Registration<T> takes ownership of the data via >> ForeignOwnable. A TypeId is stored alongside the data for runtime type >> checking, making Device::registration_data<T>() a safe method. >> >> Signed-off-by: Danilo Krummrich <[email protected]> > > The change itself LGTM. > > Reviewed-by: Alice Ryhl <[email protected]> > > But I'm not entirely convinced that this is the most convenient > user-interface. I'm wondering if the auxiliary driver trait could > specify which type the parent driver data is using in an associated > type, and whether you could eliminate the check and error path that way. > But then again, AuxiliaryDriver does not appear as a generic parameter > in auxiliary::Driver, so it might not work.
I think that's similar to what I'm suggesting in https://lore.kernel.org/rust-for-linux/[email protected]/. This does still require the type ID to exist and that probe of auxiliary drivers need to fail if type ID mismatches during probing. Best, Gary
