linux-kernel - Re: [PATCH 2/5] devres: export devres_node_init() and devres_node

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Message-ID: <CAH5fLgifC=K1wssW-nWR3wvL9OHEQ9x2hPd2+ENj_mqtgEhyxA@mail.gmail.com>
Date: Fri, 6 Feb 2026 14:20:06 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Greg KH <gregkh@...uxfoundation.org>, rafael@...nel.org, ojeda@...nel.org, 
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	lossin@...nel.org, a.hindborg@...nel.org, tmgross@...ch.edu, 
	driver-core@...ts.linux.dev, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] devres: export devres_node_init() and devres_node_add()

On Fri, Feb 6, 2026 at 2:16 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> On Fri Feb 6, 2026 at 1:34 PM CET, Greg KH wrote:
> > That's fine, because the rust driver core code should also be built into
> > the kernel, not as a module, right?
>
> Yes, but the Rust compiler may still choose to put some of the core code into
> the module.
>
> Especially with generic types and functions the Rust compiler may move some the
> generated code for a certain type instance into the module that instanciates the
> type.
>
> For instance, even though rust/kernel/devres.rs is *always* built-in, we get the
> following error when devres_node_init() is not exported when the users of this
> built-in code are built as module.
>
>         ERROR: modpost: "devres_node_init" [drivers/pwm/pwm_th1520.ko] undefined!
>         ERROR: modpost: "devres_node_init" [drivers/gpu/drm/tyr/tyr.ko] undefined!
>         ERROR: modpost: "devres_node_init" [drivers/gpu/nova-core/nova_core.ko] undefined!
>         ERROR: modpost: "devres_node_init" [samples/rust/rust_dma.ko] undefined!
>         ERROR: modpost: "devres_node_init" [samples/rust/rust_driver_pci.ko] undefined!
>         ERROR: modpost: "devres_node_init" [samples/rust/rust_driver_auxiliary.ko] undefined!
>         make[2]: *** [scripts/Makefile.modpost:147: Module.symvers] Error 1
>
> However, sprinkling "raw" EXPORT_SYMBOL_GPL() due to that is not great at all.
> Hence, we could do something like in [1] instead. I don't know if there are
> other options that may be better though.
>
> [1] https://lore.kernel.org/all/DG7UR3WWZB4V.2MYMJJH1VDHH@kernel.org/

You can use #[inline(never)] to prevent this.

Alice