Re: [PATCH v20 3/4] rust: faux: Allow retrieving a bound Device

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] The newly added invariant comment incorrectly states the faux device is 'bound to a device' instead of 'bound to a driver'.
- [Low] Missing `// INVARIANT:` comment justification for the newly added type invariant in the constructor `Registration::new()`.
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commit 4f6cdb361b5df7689eb3f97b5d9628c28576af9e
Author: Lyude Paul <lyude@redhat.com>

rust: faux: Allow retrieving a bound Device

This commit allows retrieving a Bound device context from a faux::Registration
by implementing AsRef<device::Device<device::Bound>>. It also adds a new type
invariant stating that the Registration object proves the device is bound.

> diff --git a/rust/kernel/faux.rs b/rust/kernel/faux.rs
> index 43b4974f48cd2..20ab638885354 100644
> --- a/rust/kernel/faux.rs
> +++ b/rust/kernel/faux.rs
> @@ -25,7 +25,8 @@
>  ///
>  /// # Invariants
>  ///
> -/// `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
> +/// - `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
> +/// - This object is proof that the object described by this `Registration` is bound to a device.

[Severity: Low]
This isn't a bug, but should this say "bound to a driver" instead of "bound to
a device"? A faux device is bound to a driver, not another device.

[Severity: Low]
Since a new invariant was added here, does Registration::new() need an updated
// INVARIANT: comment to justify it?

According to the subsystem guidelines, when a struct with an # Invariants
section is constructed, there must be a corresponding // INVARIANT: comment.
The current constructor only justifies the first invariant:

rust/kernel/faux.rs:Registration::new() {
    ...
        // The above function will return either a valid device, or NULL on failure
        // INVARIANT: The device will remain registered until faux_device_destroy() is called, which
        // happens in our Drop implementation.
        Ok(Self(NonNull::new(dev).ok_or(ENODEV)?))
}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260610162433.923550-1-lyude@redhat.com?part=3