[PATCH v13 0/5] rust: replace kernel::str::CStr w/ core::ffi::CStr

[Tamir Duberstein <tamird@gmail.com>]

This picks up from Michal Rostecki's work[0]. Per Michal's guidance I
have omitted Co-authored tags, as the end result is quite different.

Link: https://lore.kernel.org/rust-for-linux/20240819153656.28807-2-vadorovsky@protonmail.com/t/#u [0]
Closes: https://github.com/Rust-for-Linux/linux/issues/1075

Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
Changes in v13:
- Rebase on v6.16-rc4.
- Link to v12: https://lore.kernel.org/r/20250619-cstr-core-v12-0-80c9c7b45900@gmail.com

Changes in v12:
- Introduce `kernel::fmt::Display` to allow implementations on foreign
  types.
- Tidy up doc comment on `str_to_cstr`. (Alice Ryhl).
- Link to v11: https://lore.kernel.org/r/20250530-cstr-core-v11-0-cd9c0cbcb902@gmail.com

Changes in v11:
- Use `quote_spanned!` to avoid `use<'a, T>` and generally reduce manual
  token construction.
- Add a commit to simplify `quote_spanned!`.
- Drop first commit in favor of
  https://lore.kernel.org/rust-for-linux/20240906164448.2268368-1-paddymills@proton.me/.
  (Miguel Ojeda)
- Correctly handle expressions such as `pr_info!("{a}", a = a = a)`.
  (Benno Lossin)
- Avoid dealing with `}}` escapes, which is not needed. (Benno Lossin)
- Revert some unnecessary changes. (Benno Lossin)
- Rename `c_str_avoid_literals!` to `str_to_cstr!`. (Benno Lossin &
  Alice Ryhl).
- Link to v10: https://lore.kernel.org/r/20250524-cstr-core-v10-0-6412a94d9d75@gmail.com

Changes in v10:
- Rebase on cbeaa41dfe26b72639141e87183cb23e00d4b0dd.
- Implement Alice's suggestion to use a proc macro to work around orphan
  rules otherwise preventing `core::ffi::CStr` to be directly printed
  with `{}`.
- Link to v9: https://lore.kernel.org/r/20250317-cstr-core-v9-0-51d6cc522f62@gmail.com

Changes in v9:
- Rebase on rust-next.
- Restore `impl Display for BStr` which exists upstream[1].
- Link: https://doc.rust-lang.org/nightly/std/bstr/struct.ByteStr.html#impl-Display-for-ByteStr [1]
- Link to v8: https://lore.kernel.org/r/20250203-cstr-core-v8-0-cb3f26e78686@gmail.com

Changes in v8:
- Move `{from,as}_char_ptr` back to `CStrExt`. This reduces the diff
  some.
- Restore `from_bytes_with_nul_unchecked_mut`, `to_cstring`.
- Link to v7: https://lore.kernel.org/r/20250202-cstr-core-v7-0-da1802520438@gmail.com

Changes in v7:
- Rebased on mainline.
- Restore functionality added in commit a321f3ad0a5d ("rust: str: add
  {make,to}_{upper,lower}case() to CString").
- Used `diff.algorithm patience` to improve diff readability.
- Link to v6: https://lore.kernel.org/r/20250202-cstr-core-v6-0-8469cd6d29fd@gmail.com

Changes in v6:
- Split the work into several commits for ease of review.
- Restore `{from,as}_char_ptr` to allow building on ARM (see commit
  message).
- Add `CStrExt` to `kernel::prelude`. (Alice Ryhl)
- Remove `CStrExt::from_bytes_with_nul_unchecked_mut` and restore
  `DerefMut for CString`. (Alice Ryhl)
- Rename and hide `kernel::c_str!` to encourage use of C-String
  literals.
- Drop implementation and invocation changes in kunit.rs. (Trevor Gross)
- Drop docs on `Display` impl. (Trevor Gross)
- Rewrite docs in the style of the standard library.
- Restore the `test_cstr_debug` unit tests to demonstrate that the
  implementation has changed.

Changes in v5:
- Keep the `test_cstr_display*` unit tests.

Changes in v4:
- Provide the `CStrExt` trait with `display()` method, which returns a
   `CStrDisplay` wrapper with `Display` implementation. This addresses
   the lack of `Display` implementation for `core::ffi::CStr`.
- Provide `from_bytes_with_nul_unchecked_mut()` method in `CStrExt`,
   which might be useful and is going to prevent manual, unsafe casts.
- Fix a typo (s/preffered/prefered/).

Changes in v3:
- Fix the commit message.
- Remove redundant braces in `use`, when only one item is imported.

Changes in v2:
- Do not remove `c_str` macro. While it's preferred to use C-string
   literals, there are two cases where `c_str` is helpful:
   - When working with macros, which already return a Rust string literal
     (e.g. `stringify!`).
   - When building macros, where we want to take a Rust string literal as an
     argument (for caller's convenience), but still use it as a C-string
     internally.
- Use Rust literals as arguments in macros (`new_mutex`, `new_condvar`,
   `new_mutex`). Use the `c_str` macro to convert these literals to C-string
   literals.
- Use `c_str` in kunit.rs for converting the output of `stringify!` to a
   `CStr`.
- Remove `DerefMut` implementation for `CString`.

---
Tamir Duberstein (5):
      rust: macros: reduce collections in `quote!` macro
      rust: support formatting of foreign types
      rust: replace `CStr` with `core::ffi::CStr`
      rust: replace `kernel::c_str!` with C-Strings
      rust: remove core::ffi::CStr reexport

 drivers/block/rnull.rs                |   4 +-
 drivers/cpufreq/rcpufreq_dt.rs        |   5 +-
 drivers/gpu/drm/drm_panic_qr.rs       |   5 +-
 drivers/gpu/drm/nova/driver.rs        |  10 +-
 drivers/gpu/nova-core/driver.rs       |   6 +-
 drivers/gpu/nova-core/firmware.rs     |   2 +-
 drivers/gpu/nova-core/gpu.rs          |   4 +-
 drivers/gpu/nova-core/nova_core.rs    |   2 +-
 drivers/net/phy/ax88796b_rust.rs      |   8 +-
 drivers/net/phy/qt2025.rs             |   6 +-
 rust/kernel/auxiliary.rs              |   6 +-
 rust/kernel/block/mq.rs               |   2 +-
 rust/kernel/clk.rs                    |   9 +-
 rust/kernel/configfs.rs               |  14 +-
 rust/kernel/cpufreq.rs                |   6 +-
 rust/kernel/device.rs                 |   9 +-
 rust/kernel/devres.rs                 |   2 +-
 rust/kernel/driver.rs                 |   4 +-
 rust/kernel/drm/device.rs             |   4 +-
 rust/kernel/drm/driver.rs             |   3 +-
 rust/kernel/drm/ioctl.rs              |   2 +-
 rust/kernel/error.rs                  |  10 +-
 rust/kernel/faux.rs                   |   5 +-
 rust/kernel/firmware.rs               |  16 +-
 rust/kernel/fmt.rs                    |  89 +++++++
 rust/kernel/kunit.rs                  |  28 +--
 rust/kernel/lib.rs                    |   3 +-
 rust/kernel/miscdevice.rs             |   5 +-
 rust/kernel/net/phy.rs                |  12 +-
 rust/kernel/of.rs                     |   5 +-
 rust/kernel/pci.rs                    |   2 +-
 rust/kernel/platform.rs               |   6 +-
 rust/kernel/prelude.rs                |   5 +-
 rust/kernel/print.rs                  |   4 +-
 rust/kernel/seq_file.rs               |   6 +-
 rust/kernel/str.rs                    | 444 ++++++++++------------------------
 rust/kernel/sync.rs                   |   7 +-
 rust/kernel/sync/completion.rs        |   2 +-
 rust/kernel/sync/condvar.rs           |   4 +-
 rust/kernel/sync/lock.rs              |   4 +-
 rust/kernel/sync/lock/global.rs       |   6 +-
 rust/kernel/sync/poll.rs              |   1 +
 rust/kernel/workqueue.rs              |   9 +-
 rust/macros/fmt.rs                    |  99 ++++++++
 rust/macros/kunit.rs                  |  10 +-
 rust/macros/lib.rs                    |  19 ++
 rust/macros/module.rs                 |   2 +-
 rust/macros/quote.rs                  | 111 ++++-----
 samples/rust/rust_configfs.rs         |   9 +-
 samples/rust/rust_driver_auxiliary.rs |   7 +-
 samples/rust/rust_driver_faux.rs      |   4 +-
 samples/rust/rust_driver_pci.rs       |   4 +-
 samples/rust/rust_driver_platform.rs  |   4 +-
 samples/rust/rust_misc_device.rs      |   3 +-
 scripts/rustdoc_test_gen.rs           |   6 +-
 55 files changed, 543 insertions(+), 521 deletions(-)
---
base-commit: 769e324b66b0d92d04f315d0c45a0f72737c7494
change-id: 20250201-cstr-core-d4b9b69120cf

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