Re: [PATCH 0/2] libgpiod: Add Rust bindings

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Mon, Nov 29, 2021 at 11:42 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
>
> Hi Bartosz,
>
> This patch adds rust bindings for libgpiod v2.0, this is already partially
> tested with the virtio rust backend I am developing, which uses these to talk to
> the host kernel.
>
> This is based of the next/post-libgpiod-2.0 branch.
>
> I haven't added any mock test for this as of now and I am not sure how exactly
> am I required to add them. I did see what you mentioned in your patchset about
> mock-test vs gpio-sim stuff. Rust also have its own test-framework and I am not
> sure if that should be used instead or something else.
>
> Since I am posting this publicly for the first time, it is still named as V1. I
> have not made significant changes to the code since last time, but just divided
> the same into multiple files.
>
> --
> Viresh
>
> Viresh Kumar (2):
>   libgpiod: Generate rust FFI bindings
>   libgpiod: Add rust wrappers
>
>  .gitignore                          |   6 +
>  bindings/rust/Cargo.toml            |  14 +
>  bindings/rust/build.rs              |  60 ++++
>  bindings/rust/src/bindings.rs       |  16 ++
>  bindings/rust/src/chip.rs           | 197 +++++++++++++
>  bindings/rust/src/edge_event.rs     |  78 +++++
>  bindings/rust/src/event_buffer.rs   |  59 ++++
>  bindings/rust/src/info_event.rs     |  70 +++++
>  bindings/rust/src/lib.rs            | 268 +++++++++++++++++
>  bindings/rust/src/line_config.rs    | 431 ++++++++++++++++++++++++++++
>  bindings/rust/src/line_info.rs      | 186 ++++++++++++
>  bindings/rust/src/line_request.rs   | 218 ++++++++++++++
>  bindings/rust/src/request_config.rs | 118 ++++++++
>  bindings/rust/wrapper.h             |   2 +
>  14 files changed, 1723 insertions(+)
>  create mode 100644 bindings/rust/Cargo.toml
>  create mode 100644 bindings/rust/build.rs
>  create mode 100644 bindings/rust/src/bindings.rs
>  create mode 100644 bindings/rust/src/chip.rs
>  create mode 100644 bindings/rust/src/edge_event.rs
>  create mode 100644 bindings/rust/src/event_buffer.rs
>  create mode 100644 bindings/rust/src/info_event.rs
>  create mode 100644 bindings/rust/src/lib.rs
>  create mode 100644 bindings/rust/src/line_config.rs
>  create mode 100644 bindings/rust/src/line_info.rs
>  create mode 100644 bindings/rust/src/line_request.rs
>  create mode 100644 bindings/rust/src/request_config.rs
>  create mode 100644 bindings/rust/wrapper.h
>
> --
> 2.31.1.272.g89b43f80a514
>

Hi Viresh!

Thanks for the hard work on that. Before I even dig into the patches
themselves, I'd like to clarify a couple things (because I'm still not
sure we're on the same page) and the projected timeline for v2.

#1. The v2 API is obviously not stable yet and we're still reworking
certain structures (like line_config's accessors). This means I can't
merge the bindings just yet but I'm fine with taking them in for v2
given that the missing elements are added, which brings me to:

#2. If you look at the existing bindings, you'll notice they all have
tests implemented. These tests use the combination of whatever testing
framework was chosen for a given language and a wrapper around
libgpio-mockup that allows to use the gpio-mockup kernel module to
instantiate simulated GPIO devices. I'd like to see a comprehensive
test suite for the rust bindings too before they get into the repo.
Except that:

#3. The development of other parts of the project is currently blocked
by the gpio-sim development in the kernel. I don't want to reuse
gpio-mockup in v2 because it's simply badly designed. Currently the
v11 of the gpio-sim series[1] (based on configfs & sysfs) is on the
list and only once it lands in mainline, will we be able to advance
the tests for the C, C++ and Python interfaces. This is when the rust
tests should be developed too by following what other parts of
libgpiod do: providing a wrapper around the future libgpiosim (a
wrapper around gpio-sim configfs/sysfs interface that I'll implement
once gpio-sim is in next) and then using whatever testing framework
for rust is preferable.

#4. This one is something you could already add at this time: other
bindings contain the examples directory. Inside there are simplified
reimplementations of the gpio-tools. It would be very useful for me
(as someone not very fluent in rust) to see how those bindings are
used in practice. Could you please add it?

Thanks!
Bart

[1] https://lkml.org/lkml/2021/11/30/898