[PATCH v3 00/11] rust: use `core::ffi::CStr` method names

[PATCH v3 00/11] rust: use `core::ffi::CStr` method names

[Tamir Duberstein]

This is series 2b/5 of the migration to `core::ffi::CStr`[0].
20250704-core-cstr-prepare-v1-0-a91524037783@gmail.com.

This series depends on the prior series[0] and is intended to go through
the rust tree to reduce the number of release cycles required to
complete the work.

Subsystem maintainers: I would appreciate your `Acked-by`s so that this
can be taken through Miguel's tree (where the other series must go).

[0] https://lore.kernel.org/all/20250704-core-cstr-prepare-v1-0-a91524037783@gmail.com/

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
Changes in v3:
- Add a patch to deal with new code in acpi.
- Drop incorrectly applied Acked-by tags from Danilo.
- Link to v2: https://lore.kernel.org/r/20250719-core-cstr-fanout-1-v2-0-e1cb53f6d233@gmail.com

Changes in v2:
- Update patch title (was nova-core, now drm/panic).
- Link to v1: https://lore.kernel.org/r/20250709-core-cstr-fanout-1-v1-0-fd793b3e58a2@gmail.com

---
Tamir Duberstein (11):
      drm/panic: use `core::ffi::CStr` method names
      rust: auxiliary: use `core::ffi::CStr` method names
      rust: configfs: use `core::ffi::CStr` method names
      rust: cpufreq: use `core::ffi::CStr` method names
      rust: drm: use `core::ffi::CStr` method names
      rust: firmware: use `core::ffi::CStr` method names
      rust: kunit: use `core::ffi::CStr` method names
      rust: miscdevice: use `core::ffi::CStr` method names
      rust: net: use `core::ffi::CStr` method names
      rust: of: use `core::ffi::CStr` method names
      rust: acpi: use `core::ffi::CStr` method names

 drivers/gpu/drm/drm_panic_qr.rs | 2 +-
 rust/kernel/acpi.rs             | 7 ++-----
 rust/kernel/auxiliary.rs        | 4 ++--
 rust/kernel/configfs.rs         | 4 ++--
 rust/kernel/cpufreq.rs          | 2 +-
 rust/kernel/drm/device.rs       | 4 ++--
 rust/kernel/firmware.rs         | 2 +-
 rust/kernel/kunit.rs            | 6 +++---
 rust/kernel/miscdevice.rs       | 2 +-
 rust/kernel/net/phy.rs          | 2 +-
 rust/kernel/of.rs               | 2 +-
 samples/rust/rust_configfs.rs   | 2 +-
 12 files changed, 18 insertions(+), 21 deletions(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250709-core-cstr-fanout-1-f20611832272

Best regards,
--  
Tamir Duberstein <tamird@gmail.com>

[PATCH v3 01/11] drm/panic: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 drivers/gpu/drm/drm_panic_qr.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_panic_qr.rs b/drivers/gpu/drm/drm_panic_qr.rs
index 09a9b452e8b7..10bc5bb16992 100644
--- a/drivers/gpu/drm/drm_panic_qr.rs
+++ b/drivers/gpu/drm/drm_panic_qr.rs
@@ -948,7 +948,7 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) {
         // nul-terminated string.
         let url_cstr: &CStr = unsafe { CStr::from_char_ptr(url) };
         let segments = &[
-            &Segment::Binary(url_cstr.as_bytes()),
+            &Segment::Binary(url_cstr.to_bytes()),
             &Segment::Numeric(&data_slice[0..data_len]),
         ];
         match EncodedMsg::new(segments, tmp_slice) {

-- 
2.50.1

[PATCH v3 02/11] rust: auxiliary: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/auxiliary.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 4749fb6bffef..58be09871397 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -105,8 +105,8 @@ macro_rules! module_auxiliary_driver {
 impl DeviceId {
     /// Create a new [`DeviceId`] from name.
     pub const fn new(modname: &'static CStr, name: &'static CStr) -> Self {
-        let name = name.as_bytes_with_nul();
-        let modname = modname.as_bytes_with_nul();
+        let name = name.to_bytes_with_nul();
+        let modname = modname.to_bytes_with_nul();
 
         // TODO: Replace with `bindings::auxiliary_device_id::default()` once stabilized for
         // `const`.

-- 
2.50.1

[PATCH v3 03/11] rust: configfs: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Also avoid `Deref<Target=BStr> for CStr` as that impl doesn't exist on
`core::ffi::CStr`.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/configfs.rs       | 4 ++--
 samples/rust/rust_configfs.rs | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/configfs.rs b/rust/kernel/configfs.rs
index 2736b798cdc6..9fb5ef825e41 100644
--- a/rust/kernel/configfs.rs
+++ b/rust/kernel/configfs.rs
@@ -263,7 +263,7 @@ pub fn new(
         try_pin_init!(Self {
             group <- pin_init::init_zeroed().chain(|v: &mut Opaque<bindings::config_group>| {
                 let place = v.get();
-                let name = name.as_bytes_with_nul().as_ptr();
+                let name = name.to_bytes_with_nul().as_ptr();
                 // SAFETY: It is safe to initialize a group once it has been zeroed.
                 unsafe {
                     bindings::config_group_init_type_name(place, name.cast(), item_type.as_ptr())
@@ -613,7 +613,7 @@ impl<const ID: u64, O, Data> Attribute<ID, O, Data>
     pub const fn new(name: &'static CStr) -> Self {
         Self {
             attribute: Opaque::new(bindings::configfs_attribute {
-                ca_name: name.as_char_ptr(),
+                ca_name: crate::str::as_char_ptr_in_const_context(name),
                 ca_owner: core::ptr::null_mut(),
                 ca_mode: 0o660,
                 show: Some(Self::show),
diff --git a/samples/rust/rust_configfs.rs b/samples/rust/rust_configfs.rs
index af04bfa35cb2..5005453f874d 100644
--- a/samples/rust/rust_configfs.rs
+++ b/samples/rust/rust_configfs.rs
@@ -94,7 +94,7 @@ impl configfs::AttributeOperations<0> for Configuration {
 
     fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
         pr_info!("Show message\n");
-        let data = container.message;
+        let data = container.message.to_bytes();
         page[0..data.len()].copy_from_slice(data);
         Ok(data.len())
     }

-- 
2.50.1

[PATCH v3 04/11] rust: cpufreq: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 rust/kernel/cpufreq.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/cpufreq.rs b/rust/kernel/cpufreq.rs
index afc15e72a7c3..2bdf9ae00ffe 100644
--- a/rust/kernel/cpufreq.rs
+++ b/rust/kernel/cpufreq.rs
@@ -1018,7 +1018,7 @@ impl<T: Driver> Registration<T> {
     };
 
     const fn copy_name(name: &'static CStr) -> [c_char; CPUFREQ_NAME_LEN] {
-        let src = name.as_bytes_with_nul();
+        let src = name.to_bytes_with_nul();
         let mut dst = [0; CPUFREQ_NAME_LEN];
 
         build_assert!(src.len() <= CPUFREQ_NAME_LEN);

-- 
2.50.1

[PATCH v3 05/11] rust: drm: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/drm/device.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 3bb7c83966cf..4a51909ccc76 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -83,8 +83,8 @@ impl<T: drm::Driver> Device<T> {
         major: T::INFO.major,
         minor: T::INFO.minor,
         patchlevel: T::INFO.patchlevel,
-        name: T::INFO.name.as_char_ptr().cast_mut(),
-        desc: T::INFO.desc.as_char_ptr().cast_mut(),
+        name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
+        desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),
 
         driver_features: drm::driver::FEAT_GEM,
         ioctls: T::IOCTLS.as_ptr(),

-- 
2.50.1

[PATCH v3 06/11] rust: firmware: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/firmware.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index 1abab5b2f052..94e6bb88b903 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -291,7 +291,7 @@ const fn push_module_name(self) -> Self {
         let module_name = this.module_name;
 
         if !this.module_name.is_empty() {
-            this = this.push_internal(module_name.as_bytes_with_nul());
+            this = this.push_internal(module_name.to_bytes_with_nul());
 
             if N != 0 {
                 // Re-use the space taken by the NULL terminator and swap it with the '.' separator.

-- 
2.50.1

[PATCH v3 07/11] rust: kunit: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/kunit.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 41efd87595d6..5866cff072f9 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -102,12 +102,12 @@ unsafe impl Sync for Location {}
             unsafe impl Sync for UnaryAssert {}
 
             static LOCATION: Location = Location($crate::bindings::kunit_loc {
-                file: FILE.as_char_ptr(),
+                file: $crate::str::as_char_ptr_in_const_context(FILE),
                 line: LINE,
             });
             static ASSERTION: UnaryAssert = UnaryAssert($crate::bindings::kunit_unary_assert {
                 assert: $crate::bindings::kunit_assert {},
-                condition: CONDITION.as_char_ptr(),
+                condition: $crate::str::as_char_ptr_in_const_context(CONDITION),
                 expected_true: true,
             });
 
@@ -202,7 +202,7 @@ pub const fn kunit_case(
 ) -> kernel::bindings::kunit_case {
     kernel::bindings::kunit_case {
         run_case: Some(run_case),
-        name: name.as_char_ptr(),
+        name: kernel::str::as_char_ptr_in_const_context(name),
         attr: kernel::bindings::kunit_attributes {
             speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
         },

-- 
2.50.1

[PATCH v3 08/11] rust: miscdevice: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/miscdevice.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index 6373fe183b27..d3aa7d25afad 100644
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -34,7 +34,7 @@ pub const fn into_raw<T: MiscDevice>(self) -> bindings::miscdevice {
         // SAFETY: All zeros is valid for this C type.
         let mut result: bindings::miscdevice = unsafe { MaybeUninit::zeroed().assume_init() };
         result.minor = bindings::MISC_DYNAMIC_MINOR as ffi::c_int;
-        result.name = self.name.as_char_ptr();
+        result.name = crate::str::as_char_ptr_in_const_context(self.name);
         result.fops = MiscdeviceVTable::<T>::build();
         result
     }

-- 
2.50.1

[PATCH v3 09/11] rust: net: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/net/phy.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index 7de5cc7a0eee..be1027b7961b 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -497,7 +497,7 @@ unsafe impl Sync for DriverVTable {}
 pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
     // INVARIANT: All the fields of `struct phy_driver` are initialized properly.
     DriverVTable(Opaque::new(bindings::phy_driver {
-        name: T::NAME.as_char_ptr().cast_mut(),
+        name: crate::str::as_char_ptr_in_const_context(T::NAME).cast_mut(),
         flags: T::FLAGS,
         phy_id: T::PHY_DEVICE_ID.id(),
         phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),

-- 
2.50.1

[PATCH v3 10/11] rust: of: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Link: https://github.com/Rust-for-Linux/linux/issues/1075
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/of.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
index b76b35265df2..58b20c367f99 100644
--- a/rust/kernel/of.rs
+++ b/rust/kernel/of.rs
@@ -34,7 +34,7 @@ fn index(&self) -> usize {
 impl DeviceId {
     /// Create a new device id from an OF 'compatible' string.
     pub const fn new(compatible: &'static CStr) -> Self {
-        let src = compatible.as_bytes_with_nul();
+        let src = compatible.to_bytes_with_nul();
         // Replace with `bindings::of_device_id::default()` once stabilized for `const`.
         // SAFETY: FFI type is valid to be zero-initialized.
         let mut of: bindings::of_device_id = unsafe { core::mem::zeroed() };

-- 
2.50.1

[PATCH v3 11/11] rust: acpi: use `core::ffi::CStr` method names

[Tamir Duberstein]

Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
avoid methods that only exist on the latter.

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
 rust/kernel/acpi.rs | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/rust/kernel/acpi.rs b/rust/kernel/acpi.rs
index 7ae317368b00..37e1161c1298 100644
--- a/rust/kernel/acpi.rs
+++ b/rust/kernel/acpi.rs
@@ -37,11 +37,8 @@ impl DeviceId {
     /// Create a new device id from an ACPI 'id' string.
     #[inline(always)]
     pub const fn new(id: &'static CStr) -> Self {
-        build_assert!(
-            id.len_with_nul() <= Self::ACPI_ID_LEN,
-            "ID exceeds 16 bytes"
-        );
-        let src = id.as_bytes_with_nul();
+        let src = id.to_bytes_with_nul();
+        build_assert!(src.len() <= Self::ACPI_ID_LEN, "ID exceeds 16 bytes");
         // Replace with `bindings::acpi_device_id::default()` once stabilized for `const`.
         // SAFETY: FFI type is valid to be zero-initialized.
         let mut acpi: bindings::acpi_device_id = unsafe { core::mem::zeroed() };

-- 
2.50.1

Re: [PATCH v3 01/11] drm/panic: use `core::ffi::CStr` method names

[Jocelyn Falempe]

On 13/08/2025 17:41, Tamir Duberstein wrote:
> Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
> avoid methods that only exist on the latter.

Thanks, it looks good to me.

Acked-by: Jocelyn Falempe <jfalempe@redhat.com>

> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1075
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Reviewed-by: Benno Lossin <lossin@kernel.org>
> Acked-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> ---
>   drivers/gpu/drm/drm_panic_qr.rs | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_panic_qr.rs b/drivers/gpu/drm/drm_panic_qr.rs
> index 09a9b452e8b7..10bc5bb16992 100644
> --- a/drivers/gpu/drm/drm_panic_qr.rs
> +++ b/drivers/gpu/drm/drm_panic_qr.rs
> @@ -948,7 +948,7 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) {
>           // nul-terminated string.
>           let url_cstr: &CStr = unsafe { CStr::from_char_ptr(url) };
>           let segments = &[
> -            &Segment::Binary(url_cstr.as_bytes()),
> +            &Segment::Binary(url_cstr.to_bytes()),
>               &Segment::Numeric(&data_slice[0..data_len]),
>           ];
>           match EncodedMsg::new(segments, tmp_slice) {
> 

Re: [PATCH v3 11/11] rust: acpi: use `core::ffi::CStr` method names

[Benno Lossin]

On Wed Aug 13, 2025 at 5:42 PM CEST, Tamir Duberstein wrote:
> Prepare for `core::ffi::CStr` taking the place of `kernel::str::CStr` by
> avoid methods that only exist on the latter.
>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>

Reviewed-by: Benno Lossin <lossin@kernel.org>

---
Cheers,
Benno

> ---
>  rust/kernel/acpi.rs | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)