Upstream deprecation

The upstream sysfs interface is deprecated:

THIS ABI IS DEPRECATED, THE ABI DOCUMENTATION HAS BEEN MOVED TO
Documentation/ABI/obsolete/sysfs-gpio AND NEW USERSPACE CONSUMERS
ARE SUPPOSED TO USE THE CHARACTER DEVICE ABI. THIS OLD SYSFS ABI WILL
NOT BE DEVELOPED (NO NEW FEATURES), IT WILL JUST BE MAINTAINED.

As the bare IOCTLs may not be suitable to interact with these devices, it may be better to use libgpiod:

libgpiod - C library and tools for interacting with the linux GPIO character device (gpiod stands for GPIO device)
Since linux 4.8 the GPIO sysfs interface is deprecated. User space should use
the character device instead. This library encapsulates the ioctl calls and
data structures behind a straightforward API.

Several bindings are available, including ones for Rust:

High-level, object-oriented bindings for C++, python3 and Rust are provided....
....
Rust bindings require cargo support. When building the Rust bindings along the
C library using make, they will be automatically configured to build against the
build results of the C library.

There's also gpiod:

Rust crate for interfacing with Linux GPIO character devices.
It provides an interface to the Linux GPIO using the chardev module. This interface involves calling ioctl funcions which are unsafe and require some unintuitive variable mapping. To ease this process, this crate provides a [Chip] struct which encapsulates the interface in safe Rust functions. The functionality provided here is highly inspired by libgpiod.

And gpiocdev:

A Rust library for accessing GPIO lines on Linux platforms using the GPIO character device.
This is the equivalent of libgpiod, but in pure Rust.

gpio-cdev warns against using this crate, but this crate makes no note of anything here, and implies that this API is still supported. This is not the case, and it should be updated to account for this.

I don't have much information on this aside from what I've noted here so far, so I probably can't help much for anything.

No repository file or test is named. Start by locating the documentation that describes the sysfs GPIO API and checking its references against Linux's deprecated sysfs ABI and the character-device alternatives mentioned here, including libgpiod and Rust bindings. Done means the project documentation no longer implies the old API is current and accurately points readers to supported alternatives.