Re: [PATCH] rust: miscdevice: add registration data to MiscDevice

[Gary Guo]

On Fri Aug 7, 2026 at 4:44 PM BST, Alice Ryhl wrote:
> On Fri, Aug 7, 2026 at 4:43 PM Gary Guo <gary@xxxxxxxxxxx> wrote:
>>
>> On Fri Aug 7, 2026 at 3:22 PM BST, Alice Ryhl wrote:
>> >  impl<T: MiscDevice> MiscDeviceRegistration<T> {
>> >      /// Register a misc device.
>> > -    pub fn register(opts: MiscDeviceOptions) -> impl PinInit<Self, Error> {
>> > +    pub fn register(
>> > +        opts: MiscDeviceOptions,
>> > +        data: impl PinInit<T::RegistrationData, Error>,
>>
>> We can just skip the `RegistrationData` and use `T`?
>
> `T` is the type of the data stored per-fd. We do not separate types
> for those two concepts.

This is getting backwards though, and won't work when we need to introduce
lifetimes.

Per-fd data needs to be able to reference whatever lifetime is available on
per-reg data, so it should be assoc type of the per-reg data type. The way
around you current have causes `T::RegistrationData` to be able to reference
lifetimes on `T` which is not okay and would only work with `'static` data.

Best,
Gary

>
> Alice