Re: [PATCH v3 2/4] rust: driver: Add ACPI id table support to Adapter trait

[Igor Korotin]

> <igor.korotin.linux@xxxxxxxxx> wrote:
> >
> > Let me know if this pattern is acceptable. To my opinion it is not much
> > different from the original 2 functions conditioned by #[cfg] and
> > requires some nasty changes.
>
> In general, the more local a `cfg` can be made, the better, because we
> can share more, e.g. the docs and signature.
>
> But maybe in this case it doesn't work -- what would be the "nasty
> changes" required?

In particular on this example:
    fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
        #[cfg(not(CONFIG_OF))] {
            None
        }

        #[cfg(CONFIG_OF))] {
            // the rest of logic
        }
    }

The `dev` is marked as unused if `CONFIG_OF` is not set. So we have 3 options:
1. rename it to `_dev`. This is nasty to my opinion, because it is misleading.
2. add #[alloc(unused_variables)] on top of it. Also not good since it
will suppress
all other possible unused_variables as well.
3. The third option is `let _ = dev;` in `#[cfg(not(CONFIG_OF))]`
section. I came to
it while I was writing this reply. This looks like the best option of
three in my opinion.

Thanks
Igor