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Date: Tue, 23 Sep 2025 14:41:03 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Daniel Almeida <daniel.almeida@collabora.com>
Cc: Alice Ryhl <aliceryhl@google.com>, Miguel Ojeda <ojeda@kernel.org>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <lossin@kernel.org>,
	Andreas Hindborg <a.hindborg@kernel.org>,
	Trevor Gross <tmgross@umich.edu>,
	Danilo Krummrich <dakr@kernel.org>, linux-kernel@vger.kernel.org,
	rust-for-linux@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH 0/2] rust: usb: add initial USB abstractions
Message-ID: <2025092333-happening-eggnog-66ce@gregkh>
References: <20250825-b4-usb-v1-0-7aa024de7ae8@collabora.com>
 <2025092338-elbow-dash-373d@gregkh>
 <CAH5fLghm-syjWRrj=G2==W4PorPq47bkAPfkeJ1UAsGbbRhPfQ@mail.gmail.com>
 <B4D07104-0A10-4B04-88CC-3F138A783811@collabora.com>
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In-Reply-To: <B4D07104-0A10-4B04-88CC-3F138A783811@collabora.com>

On Tue, Sep 23, 2025 at 02:34:27PM +0200, Daniel Almeida wrote:
> […]
> 
> >> 
> >> I tried to apply these, but I get the following build error when adding
> >> to the char-misc-testing tree:
> >> 
> >> ld.lld: error: undefined symbol: usb_get_intf
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::usb::Interface as kernel::sync::aref::AlwaysRefCounted>::inc_ref) in archive vmlinux.a
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::sync::aref::ARef<kernel::usb::Interface> as core::convert::From<&kernel::usb::Interface<kernel::device::CoreInternal>>>::from) in archive vmlinux.a
> >> 
> >> ld.lld: error: undefined symbol: usb_put_intf
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::usb::Interface as kernel::sync::aref::AlwaysRefCounted>::dec_ref) in archive vmlinux.a
> >> 
> >> ld.lld: error: undefined symbol: usb_get_dev
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::usb::Device as kernel::sync::aref::AlwaysRefCounted>::inc_ref) in archive vmlinux.a
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::sync::aref::ARef<kernel::usb::Device> as core::convert::From<&kernel::usb::Device<kernel::device::CoreInternal>>>::from) in archive vmlinux.a
> >> 
> >> ld.lld: error: undefined symbol: usb_put_dev
> >>>>> referenced by kernel.1a949e63ee2acc6a-cgu.0
> >>>>>              rust/kernel.o:(<kernel::usb::Device as kernel::sync::aref::AlwaysRefCounted>::dec_ref) in archive vmlinux.a
> >> 
> >> 
> >> Any hints?
> > 
> > Did you enable CONFIG_USB?
> > 
> > Alice
> 
> +#[cfg(CONFIG_USB)]
> +pub mod usb;
> 
> Hmm, but the USB module is gated by #[cfg(CONFIG_USB) in lib.rs, so not having
> CONFIG_USB enabled should not return any errors and instead skip the USB
> bindings completely.
> 
> I wonder if this has to be CONFIG_USB=y?

It passes if CONFIG_USB=y, but it is good to keep the USB subsystem as a
module if at all possible :)

thanks,

greg k-h