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

Fabien Parent
2024-12-18T23:37:17Z

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
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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>