linux-kernel - Re: [PATCH] rust: replace `kernel::c_str!` with C-Strings in seq

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Message-Id: <DFTI0P4F3UR9.14CA9H3I19GCB@garyguo.net>
Date: Tue, 20 Jan 2026 14:49:59 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Ryan Foster" <foster.ryan.r@...il.com>,
 <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Cc: <ojeda@...nel.org>, <boqun.feng@...il.com>, <gary@...yguo.net>,
 <bjorn3_gh@...tonmail.com>, <lossin@...nel.org>, <a.hindborg@...nel.org>,
 <aliceryhl@...gle.com>, <tmgross@...ch.edu>, <gregkh@...uxfoundation.org>,
 <rafael@...nel.org>, <dakr@...nel.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] rust: replace `kernel::c_str!` with C-Strings in
 seq_file and device

On Tue Jan 20, 2026 at 2:02 PM GMT, Ryan Foster wrote:
> C-String literals were added in Rust 1.77. Replace instances of
> `kernel::c_str!` with C-String literals where possible.
>
> This patch updates seq_file and device modules to use the native
> C-string literal syntax (c"...") instead of the kernel::c_str! macro.
>
> Signed-off-by: Ryan Foster <foster.ryan.r@...il.com>
> ---
>  rust/kernel/device.rs   | 5 +----
>  rust/kernel/seq_file.rs | 4 ++--
>  2 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> index 71b200df0f40..1c3d1d962d15 100644
> --- a/rust/kernel/device.rs
> +++ b/rust/kernel/device.rs
> @@ -12,9 +12,6 @@
>  };
>  use core::{any::TypeId, marker::PhantomData, ptr};
>  
> -#[cfg(CONFIG_PRINTK)]
> -use crate::c_str;
> -
>  pub mod property;
>  
>  // Assert that we can `read()` / `write()` a `TypeId` instance from / into `struct driver_type`.
> @@ -462,7 +459,7 @@ unsafe fn printk(&self, klevel: &[u8], msg: fmt::Arguments<'_>) {
>              bindings::_dev_printk(
>                  klevel.as_ptr().cast::<crate::ffi::c_char>(),
>                  self.as_raw(),
> -                c_str!("%pA").as_char_ptr(),
> +                c"%pA".as_char_ptr(),
>                  core::ptr::from_ref(&msg).cast::<crate::ffi::c_void>(),
>              )
>          };
> diff --git a/rust/kernel/seq_file.rs b/rust/kernel/seq_file.rs
> index 855e533813a6..518265558d66 100644
> --- a/rust/kernel/seq_file.rs
> +++ b/rust/kernel/seq_file.rs
> @@ -4,7 +4,7 @@
>  //!
>  //! C header: [`include/linux/seq_file.h`](srctree/include/linux/seq_file.h)
>  
> -use crate::{bindings, c_str, fmt, str::CStrExt as _, types::NotThreadSafe, types::Opaque};
> +use crate::{bindings, fmt, str::CStrExt as _, types::NotThreadSafe, types::Opaque};

As you're changing the import list, can you also convert it to the new kernel
import style?

Best,
Gary

>  
>  /// A utility for generating the contents of a seq file.
>  #[repr(transparent)]
> @@ -36,7 +36,7 @@ pub fn call_printf(&self, args: fmt::Arguments<'_>) {
>          unsafe {
>              bindings::seq_printf(
>                  self.inner.get(),
> -                c_str!("%pA").as_char_ptr(),
> +                c"%pA".as_char_ptr(),
>                  core::ptr::from_ref(&args).cast::<crate::ffi::c_void>(),
>              );
>          }