[PATCH v13 3/5] rust: replace `CStr` with `core::ffi::CStr`

[Tamir Duberstein]

On Fri, Jul 4, 2025 at 9:00 AM Benno Lossin <lossin at kernel.org> wrote:
>
> On Tue Jul 1, 2025 at 6:49 PM CEST, Tamir Duberstein wrote:
> > `kernel::ffi::CStr` was introduced in commit d126d2380131 ("rust: str:
> > add `CStr` type") in November 2022 as an upstreaming of earlier work
> > that was done in May 2021[0]. That earlier work, having predated the
> > inclusion of `CStr` in `core`, largely duplicated the implementation of
> > `std::ffi::CStr`.
> >
> > `std::ffi::CStr` was moved to `core::ffi::CStr` in Rust 1.64 in
> > September 2022. Hence replace `kernel::str::CStr` with `core::ffi::CStr`
> > to reduce our custom code footprint, and retain needed custom
> > functionality through an extension trait.
> >
> > C-String literals were added in Rust 1.77, while our MSRV is 1.78. Thus
> > opportunistically replace instances of `kernel::c_str!` with C-String
> > literals where other code changes were already necessary or where
> > existing code triggered clippy lints; the rest will be done in a later
> > commit.
> >
> > Link: https://github.com/Rust-for-Linux/linux/commit/faa3cbcca03d0dec8f8e43f1d8d5c0860d98a23f [0]
> > Acked-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> > Reviewed-by: Alice Ryhl <aliceryhl at google.com>
> > Signed-off-by: Tamir Duberstein <tamird at gmail.com>
> > ---
> >  drivers/gpu/drm/drm_panic_qr.rs |   2 +-
> >  rust/kernel/auxiliary.rs        |   4 +-
> >  rust/kernel/configfs.rs         |   4 +-
> >  rust/kernel/cpufreq.rs          |   2 +-
> >  rust/kernel/device.rs           |   4 +-
> >  rust/kernel/drm/device.rs       |   4 +-
> >  rust/kernel/error.rs            |   4 +-
> >  rust/kernel/firmware.rs         |  11 +-
> >  rust/kernel/kunit.rs            |   6 +-
> >  rust/kernel/miscdevice.rs       |   2 +-
> >  rust/kernel/net/phy.rs          |   2 +-
> >  rust/kernel/of.rs               |   2 +-
> >  rust/kernel/prelude.rs          |   5 +-
> >  rust/kernel/seq_file.rs         |   4 +-
> >  rust/kernel/str.rs              | 394 +++++++++++-----------------------------
> >  rust/kernel/sync/condvar.rs     |   2 +-
> >  rust/kernel/sync/lock.rs        |   2 +-
> >  rust/kernel/sync/lock/global.rs |   2 +-
> >  samples/rust/rust_configfs.rs   |   2 +-
> >  19 files changed, 140 insertions(+), 318 deletions(-)
>
> Is it also possible to split this? First rename the existing functions
> on our CStr to match upstream & then you don't need to do the rename &
> removal of our CStr in the same patch?

Yes.