Re: [RFC v3 07/33] rust: drm/kms: Add drm_encoder bindings

[Maxime Ripard <mripard@kernel.org>]

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On Wed, Mar 05, 2025 at 05:59:23PM -0500, Lyude Paul wrote:
> +unsafe extern "C" fn encoder_destroy_callback<T: DriverEncoder>(
> +    encoder: *mut bindings::drm_encoder,
> +) {
> +    // SAFETY: DRM guarantees that `encoder` points to a valid initialized `drm_encoder`.
> +    unsafe { bindings::drm_encoder_cleanup(encoder) };
> +
> +    // SAFETY:
> +    // - DRM guarantees we are now the only one with access to this [`drm_encoder`].
> +    // - This cast is safe via `DriverEncoder`s type invariants.
> +    unsafe { drop(KBox::from_raw(encoder as *mut Encoder<T>)) };
> +}

I'm not sure we should expose drm_encoder_cleanup() there, if only
because it's not really up to the driver to deal with it anymore. We're
switching to drmm_encoder_alloc/init where having a destroy hook is
explicitly rejected.

Maxime

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