[PATCH 0/9] Regulator driver with I2C/Regmap Rust abstractions

[Fabien Parent <parent.f@gmail.com>]

This patch series adds a new regulator driver used by APQ8039 T2,
as well as all the Rust abstractions needed to write that driver.

This series is adding three abstractions:
* I2C: I do not expect this one to be too controversial since it is
  closely following what is done for the platform abstraction.
* Regmap: This might be the abstraction that will trigger most of the
  conversations since I took some liberties, and used what Rust has to
  offer in order provide something that seems to me user-friendly while
  also providing type-safety to ensure correct usage of the APIs.
  
  A problem I faced is that 'struct regmap' is not reference counted,
  and pointer to it are being held in several places. In C it is
  mostly expected to use devm_ API during allocation and forget about
  the pointer lifetime, but this does not seem idiomatic to rust since
  one would expect that the `Regmap` structure to be deinited and
  deallocated when dropped. I was hesitating between adding a refcount
  to the C API, or maintain some form of refcount by wrapping the
  structure into a Arc, and making sure that each abstraction for C code
  that hold a pointer to a regmap would keep a Arc<Regmap> instance.
  I chose to do the later for simplicity.
* Regulator driver: This one contains the bare minimum to write the
  ncv6336 drivers. I also have an abstraction for the consumer part, but
  it will come later in another patch series for another driver.

Dependencies:
[1] Entire series depends on the patch series from Danilo adding Device
and OF Rust abstractions: 2024121550-palpitate-exhume-348c@gregkh
[2] "rust: add abstraction for regmap" depends on genmask:
CAH5fLgjOKQdKViAGArMjvXjVmYpbo_sA8xoQGwu+DCW1FDFRXA@mail.gmail.com
[3] "rust: regulator: add support for regmap" depends on the Sealed trait:
20230224-rust-iopt-rtkit-v1-1-49ced3391295@asahilina.net

A while ago when Rust support was close to getting merged in the kernel
I decided to learn Rust to see what the fuss was about and see if I
could help contribute to it. Since then I've been working on a few drivers
during my free time, but my code was depending on too much out-of-tree
code. With the patch series [1] getting close to being merged, it was
finally time to send my code to the mailing list, so here it is.

Happy reviewing!

Fabien

Signed-off-by: Fabien Parent <fabien.parent@linaro.org>
---
Fabien Parent (8):
      rust: add abstraction for regmap
      rust: error: add declaration for ENOTRECOVERABLE error
      rust: regulator: add abstraction for Regulator's modes
      rust: regulator: add Regulator Driver abstraction
      rust: regulator: add support for regmap
      dt-bindings: regulator: add binding for ncv6336 regulator
      regulator: add driver for ncv6336 regulator
      arm64: dts: qcom: apq8039-t2: add node for ncv6336 regulator

Fiona Behrens (1):
      rust: i2c: add basic I2C client abstraction

 .../bindings/regulator/onnn,ncv6336.yaml           |   54 +
 MAINTAINERS                                        |    4 +
 arch/arm64/boot/dts/qcom/apq8039-t2.dts            |   23 +
 drivers/regulator/Kconfig                          |    7 +
 drivers/regulator/Makefile                         |    1 +
 drivers/regulator/ncv6336_regulator.rs             |  241 +++++
 rust/bindings/bindings_helper.h                    |    4 +
 rust/helpers/helpers.c                             |    2 +
 rust/helpers/i2c.c                                 |   13 +
 rust/helpers/regmap.c                              |   48 +
 rust/kernel/error.rs                               |    1 +
 rust/kernel/i2c.rs                                 |  288 ++++++
 rust/kernel/lib.rs                                 |    6 +
 rust/kernel/regmap.rs                              | 1043 ++++++++++++++++++++
 rust/kernel/regulator.rs                           |   44 +
 rust/kernel/regulator/driver.rs                    |  991 +++++++++++++++++++
 16 files changed, 2770 insertions(+)
---
base-commit: 26033691d5821bb493dd3426140939d0a79cd480
change-id: 20241025-ncv6336-12324a94c693
prerequisite-message-id: <2024121550-palpitate-exhume-348c@gregkh>
prerequisite-patch-id: b798fb7308e85f8cd237e3de0c33f3079eec29b8
prerequisite-patch-id: ac93ef5057cbb09cf886223c4f10e53eeec1d234
prerequisite-patch-id: ea80287941ef43f59fa75a28e6798ff10c8e90c1
prerequisite-patch-id: 482d8f7c10b0b79fb5d06e3718fd6da0fdd0dfa2
prerequisite-patch-id: cd9756c9586f394e5b39198497979aa1384ad2b8
prerequisite-patch-id: 313083700e67eab809a6b673d1fd835a6bd18625
prerequisite-patch-id: d0c7198d84ffa229221bbe06541136c97e8aae4e
prerequisite-patch-id: 0c4e157879b92f366feca2e89b5719e0a9bfa36a
prerequisite-patch-id: 515464a50ad216e2e9811043db8ca341262db288
prerequisite-patch-id: c50da45a4d7e62930f78b854f9afc636120dc255
prerequisite-patch-id: 5e32316afbfed41fe68cc096bf5a93201d0c65f9
prerequisite-patch-id: 15b08041af5e8f50619e3098b01ac0c0c0357751
prerequisite-patch-id: 3feaab560cf92641ee1af4e07cd5cb2a50aa36a5
prerequisite-patch-id: 14a272276db1704d58a2afc140da51826347a90e
prerequisite-patch-id: c79292d0686dd843cf25f5a2300445e410e99d13
prerequisite-patch-id: ea5c28331c595ad00929291b483c8848f3ff84cf
prerequisite-patch-id: 69858ba82eb5852a4e7e36d084d2917ba4e8a6cd
prerequisite-patch-id: 3f1b33691d5ad742f689a90d41bfd37244ff4133

Best regards,
-- 
Fabien Parent <parent.f@gmail.com>