[PATCH v4 00/15] rnull: add configfs, remote completion to rnull

[Andreas Hindborg <a.hindborg@kernel.org>]

This series adds configuration via configfs and remote completion to
the rnull driver. The series also includes a set of changes to the
rust block device driver API: a few cleanup patches, and a few features
supporting the rnull changes.

The series removes the raw buffer formatting logic from `kernel::block`
and improves the logic available in `kernel::string` to support the same
use as the removed logic.

This series is a smaller subset of the patches available in the
downstream rnull tree. I hope to minimize the delta between upstream
and downstream over the next few kernel releases.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Changes in v4:
- Rebase on v6.17-rc1
- Merge patches that expose `str::{Formatter, RawFormatter}` publicly.
- Remove `NullTerminatedFormatter::from_array`.
- Change signature of `Formatter::new`.
- Change invariant wording for `NullTerminatedFormatter`.
- Add missing period in comment for `SECTOR_MASK`.
- Rephrase docstring for PAGE_SECTORS_SHIFT.
- Use `write_str` rather than `write_fmt` where applicable.
- Improve boolean parsing in rnull configfs interface.
- Be explicit when intentionally dropping data (GenDisk::drop).
- Add minimum size invariant to `NullTerminatedFormatter`.
- Import `EINVAL` from the prelude.
- Link to v3: https://lore.kernel.org/r/20250711-rnull-up-v6-16-v3-0-3a262b4e2921@kernel.org

Changes in v3:
- Rename `NullBorrowFormatter` as `NullTerminatedFormatter`.
- Remove `pos` from `NullBorrowFormatter`.
- Call into `Self::new` in `NullBorrowFormatter::from_array`.
- Use `Option` return type in `NullBorrowFormatter::from_array`
- Use `Option` return type in `NullBorrowFormatter::new`.
- Remove `BorrowFormatter` and update `Formatter` with a generic lifetime.
- Split visibility change of `str::Formatter` into separate patch.
- Link to v2: https://lore.kernel.org/r/20250708-rnull-up-v6-16-v2-0-ab93c0ff429b@kernel.org

Changes in v2:
- Rework formatter logic. Add two new formatters that write to slices,
  one of which adds a trailing null byte.
- Reorder and split patches so that changes are more clear.
- Fix a typo in soft-irq patch summary.
- Link to v1: https://lore.kernel.org/r/20250616-rnull-up-v6-16-v1-0-a4168b8e76b2@kernel.org

---
Andreas Hindborg (15):
      rust: str: normalize imports in `str.rs`
      rust: str: allow `str::Formatter` to format into `&mut [u8]`.
      rust: str: expose `str::{Formatter, RawFormatter}` publicly.
      rust: str: introduce `NullTerminatedFormatter`
      rust: block: normalize imports for `gen_disk.rs`
      rust: block: use `NullTerminatedFormatter`
      rust: block: remove `RawWriter`
      rust: block: remove trait bound from `mq::Request` definition
      rust: block: add block related constants
      rnull: move driver to separate directory
      rnull: enable configuration via `configfs`
      rust: block: add `GenDisk` private data support
      rust: block: mq: fix spelling in a safety comment
      rust: block: add remote completion to `Request`
      rnull: add soft-irq completion support

 MAINTAINERS                        |   2 +-
 drivers/block/Kconfig              |  10 +-
 drivers/block/Makefile             |   4 +-
 drivers/block/rnull.rs             |  80 -----------
 drivers/block/rnull/Kconfig        |  13 ++
 drivers/block/rnull/Makefile       |   3 +
 drivers/block/rnull/configfs.rs    | 273 +++++++++++++++++++++++++++++++++++++
 drivers/block/rnull/rnull.rs       | 105 ++++++++++++++
 rust/kernel/block.rs               |  13 ++
 rust/kernel/block/mq.rs            |  14 +-
 rust/kernel/block/mq/gen_disk.rs   |  58 ++++++--
 rust/kernel/block/mq/operations.rs |  65 +++++++--
 rust/kernel/block/mq/raw_writer.rs |  55 --------
 rust/kernel/block/mq/request.rs    |  21 ++-
 rust/kernel/str.rs                 |  83 +++++++++--
 15 files changed, 608 insertions(+), 191 deletions(-)
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250616-rnull-up-v6-16-b4571e28feee

Best regards,
-- 
Andreas Hindborg <a.hindborg@kernel.org>