make InPlaceInit compatible with Arc

[y86-dev]

Currently InPlaceInit is not implemented for Arc, because pin_init() returns a Pin<Self>. But Arc implicitly pins its contents, so the return type should actually be just Self.

Add an associated type to InPlaceInit that is then used as the return type. Also implement InPlaceInit for Arc and ListArc if available ¹.

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This requires submitting a proper patch to the LKML and the Rust for Linux mailing list. Please recall to test your changes, to use a proper title for the commit, to sign your commit under the Developer's Certificate of Origin and so on. Please see https://docs.kernel.org/process/submitting-patches.html and https://rust-for-linux.com/contributing for details.

Please take this issue only if you are new to the kernel development process and you would like to use it as a test to submit your first patch to the kernel. Please do not take it if you do not plan to make other contributions to the kernel.

Footnotes

1. Note that currently only v1 of the list abstractions exist, so ListArc might not be upstreamed. ↩

[ellcs]

Hi! I am new to the kernel development, and this looks doable to me. So I work on this.