Full Code of rust-embedded/linux-embedded-hal for AI

Repository: rust-embedded/linux-embedded-hal
Branch: master
Commit: e9ccbf9e0b71
Files: 20
Total size: 65.6 KB

Directory structure:
gitextract_x2z4flh9/

├── .github/
│   ├── CODEOWNERS
│   └── workflows/
│       ├── ci.yml
│       ├── clippy.yml
│       └── rustfmt.yml
├── .gitignore
├── CHANGELOG.md
├── CODE_OF_CONDUCT.md
├── Cargo.toml
├── LICENSE-APACHE
├── LICENSE-MIT
├── README.md
├── examples/
│   └── transactional-i2c.rs
└── src/
    ├── cdev_pin.rs
    ├── delay.rs
    ├── i2c.rs
    ├── lib.rs
    ├── serial.rs
    ├── spi.rs
    ├── sysfs_pin.rs
    └── timer.rs

================================================
FILE CONTENTS
================================================

================================================
FILE: .github/CODEOWNERS
================================================
* @rust-embedded/embedded-linux


================================================
FILE: .github/workflows/ci.yml
================================================
on:
  push: # Run CI for all branches except GitHub merge queue tmp branches
    branches-ignore:
    - "gh-readonly-queue/**"
  pull_request: # Run CI for PRs on any branch
  merge_group: # Run CI for the GitHub merge queue

name: Continuous integration

jobs:
  ci-linux:
    name: CI
    runs-on: ubuntu-latest

    strategy:
      fail-fast: false
      matrix:
        rust: [stable]
        target: [x86_64-unknown-linux-gnu, armv7-unknown-linux-gnueabihf]
        features:
          - ''
          - 'async-tokio,gpio_cdev,gpio_sysfs,i2c,spi'

        include:
          - rust: 1.84.0 # MSRV
            target: x86_64-unknown-linux-gnu

          # Test nightly but don't fail
          - rust: nightly
            experimental: true
            target: x86_64-unknown-linux-gnu

    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@master
        with:
          toolchain: ${{ matrix.rust }}
          target: ${{ matrix.target }}

      - name: Install armv7 libraries
        if: ${{ matrix.target == 'armv7-unknown-linux-gnueabihf' }}
        run: |
            sudo apt-get update
            sudo apt-get install -y libc6-armhf-cross libc6-dev-armhf-cross gcc-arm-linux-gnueabihf

      - run: cargo check --target=${{ matrix.target }} --features=${{ matrix.features }}


================================================
FILE: .github/workflows/clippy.yml
================================================
on:
  push: # Run CI for all branches except GitHub merge queue tmp branches
    branches-ignore:
    - "gh-readonly-queue/**"
  pull_request: # Run CI for PRs on any branch
  merge_group: # Run CI for the GitHub merge queue

name: Clippy check
jobs:
  clippy_check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@master
        with:
          toolchain: 1.84.0
          components: clippy
      - run: cargo clippy --all-features -- --deny=warnings


================================================
FILE: .github/workflows/rustfmt.yml
================================================
on:
  push: # Run CI for all branches except GitHub merge queue tmp branches
    branches-ignore:
    - "gh-readonly-queue/**"
  pull_request: # Run CI for PRs on any branch
  merge_group: # Run CI for the GitHub merge queue

name: Code formatting check

jobs:
  fmt:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: dtolnay/rust-toolchain@master
        with:
          toolchain: nightly
          components: rustfmt
      - run: cargo fmt --check


================================================
FILE: .gitignore
================================================

/target/
**/*.rs.bk
Cargo.lock


================================================
FILE: CHANGELOG.md
================================================
# Change Log

All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](http://keepachangelog.com/)
and this project adheres to [Semantic Versioning](http://semver.org/).

## [Unreleased]

### Changed

- MSRV is now 1.84.0.
- Set `resolver = "3"`, which implies `resolver.incompatible-rust-versions = "fallback"`

### Added

- Added async `DelayNs` implementation for `tokio`.
- Added feature flag for `serial`.

### Fixed

- Fix UB (and remove unsafe block) in handling of SpiOperation::TransferInPlace

## [v0.4.0] - 2024-01-10

### Changed
- Updated to `embedded-hal` `1.0.0` release ([API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal/CHANGELOG.md#v100---2023-12-28))
- Updated to `embedded-hal-nb` `1.0.0` release ([API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal-nb/CHANGELOG.md#v100---2023-12-28))

## [v0.4.0-alpha.4] - 2024-01-03

### Changed
- [breaking-change] Replace serial-rs with the serialport-rs crate. `Serial::open` now needs a baud-rate argument as well.
- [breaking-change] Split `Spidev` into `SpidevDevice` and `SpidevBus`, implementing the respective `SpiDevice` and `SpiBus` traits (#100)
- Updated to `embedded-hal` `1.0.0-rc.3` release ([API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal/CHANGELOG.md#v100-rc3---2023-12-14))
- Updated to `embedded-hal-nb` `1.0.0-rc.3` release ([API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal-nb/CHANGELOG.md#v100-rc3---2023-12-14))
- Updated to `spidev` `0.6.0` release([API changes](https://github.com/rust-embedded/rust-spidev/blob/master/CHANGELOG.md#060--2023-08-03))
- Updated to `i2cdev` `0.6.0` release([API changes](https://github.com/rust-embedded/rust-i2cdev/blob/master/CHANGELOG.md#v060---2023-08-03))
- Updated to `gpio_cdev` `0.6.0` release([API changes](https://github.com/rust-embedded/gpio-cdev/blob/master/CHANGELOG.md#v060--2023-09-11))
- Updated to `nix` `0.27.1`
- MSRV is now 1.65.0.

### Fixed
- Fix using SPI transfer with unequal buffer sizes (#97, #98).

## [v0.4.0-alpha.3] - 2022-08-04

### Added

- Added feature flag for `spi` and `i2c`

### Changed

- Updated to `embedded-hal` `1.0.0-alpha.8` release ([API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal/CHANGELOG.md#v100-alpha8---2022-04-15))

## [v0.4.0-alpha.2] - 2022-02-15

### Added

- Mappings for `embedded-hal` error kinds
### Changed

- Updated to `embedded-hal` `1.0.0-alpha.7` release (significant [API changes](https://github.com/rust-embedded/embedded-hal/blob/master/embedded-hal/CHANGELOG.md#v100-alpha7---2022-02-09))
- Updated dependencies to force use of newer nix version
  - `spidev` to version `0.5.1`
  - `i2cdev` to version `0.5.1`
  - `gpio-cdev` to version `0.5.1`
  - `sysfs_gpio` to version `0.6.1`

## [v0.4.0-alpha.1] - 2021-10-07

### Added

- Implement `embedded_hal::digital::blocking::IoPin` for `CdevPin` and `SysfsPin`
- `CountDown` implementation for `SysTimer`.
- `Default` implementation for `SysTimer`.

### Changed

- Modified `OutputPin` behavior for active-low pins to match `InputPin` behavior.
- Set default features to build both sysfs and cdev pin types.
- Removed `Pin` export, use `CdevPin` or `SysfsPin`.
- Adapted to `embedded-hal` `1.0.0-alpha.5` release.
- Increased the Minimum Supported Rust Version to `1.46.0` due to an update of `bitflags`.
- Updated `spidev` to version `0.5`.
- Updated `i2cdev` to version `0.5`.
- Updated `gpio-cdev` to version `0.5`.
- Updated `sysfs_gpio` to version `0.6`.
- Updated `nb` to version `1`.

## [v0.3.2] - 2021-10-25

### Fixed
- Readd `Pin` type export as an alias to `SysfsPin` for compatibility with the `0.3.0` version.

## [v0.3.1] - 2021-09-27
### Added

- Added implementation of transactional SPI and I2C traits.
- `CountDown` implementation for `SysTimer`.
- `Default` implementation for `SysTimer`.

### Changed

- Set default features to build both sysfs and cdev pin types.
- Removed `Pin` export, use `CdevPin` or `SysfsPin`.
- Updated `embedded-hal` to version `0.2.6`.
- Updated `nb` to version `0.1.3`.
- Updated `gpio-cdev` to version `0.5`.
- Updated `i2cdev` to version `0.5`.
- Updated `spidev` to version `0.5`.
- Updated `sysfs-gpio` to version `0.6`.
- Updated `cast` to version `0.3`.

### Fixed

- Modified `OutputPin` behavior for active-low pins to match `InputPin` behavior.

## [v0.3.0] - 2019-11-25

### Added

- Added serial::Read/Write implementation.
- Added feature flag for Chardev GPIO

### Fixed

- Do write and read in one transaction in WriteRead implementation.
- Removed #[deny(warnings)]

### Changed

- Use embedded-hal::digital::v2 traits.
- Updated to i2cdev 0.4.3 (necessary for trasactional write-read).
- Updated to spidev 0.4
- Added feature flag for Sysfs GPIO

## [v0.2.2] - 2018-12-21

### Changed

- updated to i2cdev 0.4.1 (removes superflous dependencies)

## [v0.2.1] - 2018-10-25

### Added

- implementation of the unproven `embedded_hal::::digital::InputPin` trait.

## [v0.2.0] - 2018-05-14

### Changed

- [breaking-change] moved to v0.2.x of `embedded-hal`.

## [v0.1.1] - 2018-02-13

### Added

- implementation of `embedded_hal::blocking::Delay*` traits in the form of the `Delay` zero sized
  type.

- implementation of the `embedded_hal::blocking::i2c` traits in the form of the `I2cdev` newtype.

## v0.1.0 - 2018-01-17

Initial release

[Unreleased]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.4.0...HEAD
[v0.4.0]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.4.0-alpha.4...v0.4.0
[v0.4.0-alpha.4]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.4.0-alpha.3...v0.4.0-alpha.4
[v0.4.0-alpha.3]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.4.0-alpha.2...v0.4.0-alpha.3
[v0.4.0-alpha.2]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.4.0-alpha.1...v0.4.0-alpha.2
[v0.4.0-alpha.1]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.3.0...v0.4.0-alpha.1
[v0.3.2]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.3.1...v0.3.2
[v0.3.1]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.3.0...v0.3.1
[v0.3.0]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.2.2...v0.3.0
[v0.2.2]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.2.1...v0.2.2
[v0.2.1]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.2.0...v0.2.1
[v0.2.0]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.1.1...v0.2.0
[v0.1.1]: https://github.com/rust-embedded/linux-embedded-hal/compare/v0.1.0...v0.1.1


================================================
FILE: CODE_OF_CONDUCT.md
================================================
# The Rust Code of Conduct

## Conduct

**Contact**: [HAL team](https://github.com/rust-embedded/wg#the-hal-team)

* We are committed to providing a friendly, safe and welcoming environment for all, regardless of level of experience, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, ethnicity, age, religion, nationality, or other similar characteristic.
* On IRC, please avoid using overtly sexual nicknames or other nicknames that might detract from a friendly, safe and welcoming environment for all.
* Please be kind and courteous. There's no need to be mean or rude.
* Respect that people have differences of opinion and that every design or implementation choice carries a trade-off and numerous costs. There is seldom a right answer.
* Please keep unstructured critique to a minimum. If you have solid ideas you want to experiment with, make a fork and see how it works.
* We will exclude you from interaction if you insult, demean or harass anyone. That is not welcome behavior. We interpret the term "harassment" as including the definition in the [Citizen Code of Conduct](http://citizencodeofconduct.org/); if you have any lack of clarity about what might be included in that concept, please read their definition. In particular, we don't tolerate behavior that excludes people in socially marginalized groups.
* Private harassment is also unacceptable. No matter who you are, if you feel you have been or are being harassed or made uncomfortable by a community member, please contact one of the channel ops or any of the [HAL team][team] immediately. Whether you're a regular contributor or a newcomer, we care about making this community a safe place for you and we've got your back.
* Likewise any spamming, trolling, flaming, baiting or other attention-stealing behavior is not welcome.

## Moderation

These are the policies for upholding our community's standards of conduct.

1. Remarks that violate the Rust standards of conduct, including hateful, hurtful, oppressive, or exclusionary remarks, are not allowed. (Cursing is allowed, but never targeting another user, and never in a hateful manner.)
2. Remarks that moderators find inappropriate, whether listed in the code of conduct or not, are also not allowed.
3. Moderators will first respond to such remarks with a warning.
4. If the warning is unheeded, the user will be "kicked," i.e., kicked out of the communication channel to cool off.
5. If the user comes back and continues to make trouble, they will be banned, i.e., indefinitely excluded.
6. Moderators may choose at their discretion to un-ban the user if it was a first offense and they offer the offended party a genuine apology.
7. If a moderator bans someone and you think it was unjustified, please take it up with that moderator, or with a different moderator, **in private**. Complaints about bans in-channel are not allowed.
8. Moderators are held to a higher standard than other community members. If a moderator creates an inappropriate situation, they should expect less leeway than others.

In the Rust community we strive to go the extra step to look out for each other. Don't just aim to be technically unimpeachable, try to be your best self. In particular, avoid flirting with offensive or sensitive issues, particularly if they're off-topic; this all too often leads to unnecessary fights, hurt feelings, and damaged trust; worse, it can drive people away from the community entirely.

And if someone takes issue with something you said or did, resist the urge to be defensive. Just stop doing what it was they complained about and apologize. Even if you feel you were misinterpreted or unfairly accused, chances are good there was something you could've communicated better — remember that it's your responsibility to make your fellow Rustaceans comfortable. Everyone wants to get along and we are all here first and foremost because we want to talk about cool technology. You will find that people will be eager to assume good intent and forgive as long as you earn their trust.

The enforcement policies listed above apply to all official embedded WG venues; including official IRC channels (#rust-embedded); GitHub repositories under rust-embedded; and all forums under rust-embedded.org (forum.rust-embedded.org).

*Adapted from the [Node.js Policy on Trolling](http://blog.izs.me/post/30036893703/policy-on-trolling) as well as the [Contributor Covenant v1.3.0](https://www.contributor-covenant.org/version/1/3/0/).*

[team]: https://github.com/rust-embedded/wg#the-hal-team


================================================
FILE: Cargo.toml
================================================
[package]
authors = [
    "The Embedded Linux Team <embedded-linux@teams.rust-embedded.org>",
    "Jorge Aparicio <jorge@japaric.io>"
]
categories = ["embedded", "hardware-support"]
description = "Implementation of the `embedded-hal` traits for Linux devices"
keywords = ["Linux", "hal"]
license = "MIT OR Apache-2.0"
name = "linux-embedded-hal"
repository = "https://github.com/rust-embedded/linux-embedded-hal"
version = "0.5.0-alpha.0"
edition = "2018"
rust-version = "1.84"
resolver = "3"

[features]
gpio_sysfs = ["sysfs_gpio"]
gpio_cdev = ["gpio-cdev"]
async-tokio = ["gpio-cdev/async-tokio", "dep:embedded-hal-async", "tokio/time"]
i2c = ["i2cdev", "nix"]
spi = ["spidev"]
serial = ["serialport", "embedded-hal-nb"]

default = [ "gpio_cdev", "gpio_sysfs", "i2c", "spi", "serial" ]

[dependencies]
embedded-hal = "1"
embedded-hal-nb = { version = "1", optional = true }
embedded-hal-async = { version = "1", optional = true }
gpio-cdev = { version = "0.6.0", optional = true }
sysfs_gpio = { version = "0.6.1", optional = true }
i2cdev = { version = "0.6.0", optional = true }
nb = "1"
serialport = { version = "4.2.0", default-features = false, optional = true }
spidev = { version = "0.6.1", optional = true }
nix = { version = "0.27.1", optional = true }
tokio = { version = "1", default-features = false, optional = true }

[dev-dependencies]
openpty = "0.2.0"

[dependencies.cast]
# we don't need the `Error` implementation
default-features = false
version = "0.3"


================================================
FILE: LICENSE-APACHE
================================================
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limitations under the License.


================================================
FILE: LICENSE-MIT
================================================
Copyright (c) 2018 Jorge Aparicio
Copyright (c) 2019-2024 The Rust embedded linux team and contributors.

Permission is hereby granted, free of charge, to any
person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the
Software without restriction, including without
limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software
is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice
shall be included in all copies or substantial portions
of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.


================================================
FILE: README.md
================================================
[![crates.io](https://img.shields.io/crates/d/linux-embedded-hal.svg)](https://crates.io/crates/linux-embedded-hal)
[![crates.io](https://img.shields.io/crates/v/linux-embedded-hal.svg)](https://crates.io/crates/linux-embedded-hal)
[![Documentation](https://docs.rs/linux-embedded-hal/badge.svg)](https://docs.rs/linux-embedded-hal)
![Minimum Supported Rust Version](https://img.shields.io/badge/rustc-1.84+-blue.svg)

# `linux-embedded-hal`

> Implementation of the [`embedded-hal`] traits for Linux devices

This project is developed and maintained by the [Embedded Linux team][team].

[`embedded-hal`]: https://crates.io/crates/embedded-hal

## [Documentation](https://docs.rs/linux-embedded-hal)

## GPIO character device

Since Linux kernel v4.4 the use of sysfs GPIO was deprecated and replaced by the character device GPIO.
See [gpio-cdev documentation](https://github.com/rust-embedded/gpio-cdev#sysfs-gpio-vs-gpio-character-device) for details.

This crate includes feature flag `gpio_cdev` that exposes `CdevPin` as wrapper around `LineHandle` from [gpio-cdev](https://crates.io/crates/gpio-cdev).
To enable it update your Cargo.toml. Please note that in order to prevent `LineHandle` fd from closing you should
assign to a variable, see [cdev issue](https://github.com/rust-embedded/gpio-cdev/issues/29) for more details.
```
linux-embedded-hal = { version = "0.4", features = ["gpio_cdev"] }
```

`SysfsPin` can be still used with feature flag `gpio_sysfs`.

With `default-features = false` you can enable the features `gpio_cdev`, `gpio_sysfs`, `i2c`, and `spi` as needed.

## Minimum Supported Rust Version (MSRV)

This crate is guaranteed to compile on stable Rust 1.84.0 and up. It *might*
compile with older versions but that may change in any new patch release.

## License

Licensed under either of

- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
  http://www.apache.org/licenses/LICENSE-2.0)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)

at your option.

### Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.

## Code of Conduct

Contribution to this crate is organized under the terms of the [Rust Code of
Conduct][CoC], the maintainer of this crate, the [HAL team][team], promises
to intervene to uphold that code of conduct.

[CoC]: CODE_OF_CONDUCT.md
[team]: https://github.com/rust-embedded/wg/#the-embedded-linux-team


================================================
FILE: examples/transactional-i2c.rs
================================================
use embedded_hal::i2c::{I2c, Operation as I2cOperation};
use linux_embedded_hal::I2cdev;

const ADDR: u8 = 0x12;

struct Driver<I2C> {
    i2c: I2C,
}

impl<I2C> Driver<I2C>
where
    I2C: I2c,
{
    pub fn new(i2c: I2C) -> Self {
        Driver { i2c }
    }

    fn read_something(&mut self) -> Result<u8, I2C::Error> {
        let mut read_buffer = [0];
        let mut ops = [
            I2cOperation::Write(&[0xAB]),
            I2cOperation::Read(&mut read_buffer),
        ];
        self.i2c.transaction(ADDR, &mut ops).and(Ok(read_buffer[0]))
    }
}

fn main() {
    let dev = I2cdev::new("/dev/i2c-1").unwrap();
    let mut driver = Driver::new(dev);
    let value = driver.read_something().unwrap();
    println!("Read value: {}", value);
}


================================================
FILE: src/cdev_pin.rs
================================================
//! Implementation of [`embedded-hal`] digital input/output traits using a Linux CDev pin
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use std::fmt;

/// Newtype around [`gpio_cdev::LineHandle`] that implements the `embedded-hal` traits
///
/// [`gpio_cdev::LineHandle`]: https://docs.rs/gpio-cdev/0.5.0/gpio_cdev/struct.LineHandle.html
pub struct CdevPin(pub gpio_cdev::LineHandle, gpio_cdev::LineInfo);

impl CdevPin {
    /// See [`gpio_cdev::Line::request`][0] for details.
    ///
    /// [0]: https://docs.rs/gpio-cdev/0.5.0/gpio_cdev/struct.Line.html#method.request
    pub fn new(handle: gpio_cdev::LineHandle) -> Result<Self, gpio_cdev::errors::Error> {
        let info = handle.line().info()?;
        Ok(CdevPin(handle, info))
    }

    fn get_input_flags(&self) -> gpio_cdev::LineRequestFlags {
        if self.1.is_active_low() {
            return gpio_cdev::LineRequestFlags::INPUT | gpio_cdev::LineRequestFlags::ACTIVE_LOW;
        }
        gpio_cdev::LineRequestFlags::INPUT
    }

    fn get_output_flags(&self) -> gpio_cdev::LineRequestFlags {
        let mut flags = gpio_cdev::LineRequestFlags::OUTPUT;
        if self.1.is_active_low() {
            flags.insert(gpio_cdev::LineRequestFlags::ACTIVE_LOW);
        }
        if self.1.is_open_drain() {
            flags.insert(gpio_cdev::LineRequestFlags::OPEN_DRAIN);
        } else if self.1.is_open_source() {
            flags.insert(gpio_cdev::LineRequestFlags::OPEN_SOURCE);
        }
        flags
    }

    /// Set this pin to input mode
    pub fn into_input_pin(self) -> Result<CdevPin, gpio_cdev::errors::Error> {
        if self.1.direction() == gpio_cdev::LineDirection::In {
            return Ok(self);
        }
        let line = self.0.line().clone();
        let input_flags = self.get_input_flags();
        let consumer = self.1.consumer().unwrap_or("").to_owned();

        // Drop self to free the line before re-requesting it in a new mode.
        std::mem::drop(self);

        CdevPin::new(line.request(input_flags, 0, &consumer)?)
    }

    /// Set this pin to output mode
    pub fn into_output_pin(
        self,
        state: embedded_hal::digital::PinState,
    ) -> Result<CdevPin, gpio_cdev::errors::Error> {
        if self.1.direction() == gpio_cdev::LineDirection::Out {
            return Ok(self);
        }

        let line = self.0.line().clone();
        let output_flags = self.get_output_flags();
        let consumer = self.1.consumer().unwrap_or("").to_owned();

        // Drop self to free the line before re-requesting it in a new mode.
        std::mem::drop(self);

        let is_active_low = output_flags.intersects(gpio_cdev::LineRequestFlags::ACTIVE_LOW);
        CdevPin::new(line.request(
            output_flags,
            state_to_value(state, is_active_low),
            &consumer,
        )?)
    }
}

/// Converts a pin state to the gpio_cdev compatible numeric value, accounting
/// for the active_low condition.
fn state_to_value(state: embedded_hal::digital::PinState, is_active_low: bool) -> u8 {
    if is_active_low {
        match state {
            embedded_hal::digital::PinState::High => 0,
            embedded_hal::digital::PinState::Low => 1,
        }
    } else {
        match state {
            embedded_hal::digital::PinState::High => 1,
            embedded_hal::digital::PinState::Low => 0,
        }
    }
}

/// Error type wrapping [gpio_cdev::errors::Error](gpio_cdev::errors::Error) to implement [embedded_hal::digital::Error]
#[derive(Debug)]
pub struct CdevPinError {
    err: gpio_cdev::errors::Error,
}

impl CdevPinError {
    /// Fetch inner (concrete) [`gpio_cdev::errors::Error`]
    pub fn inner(&self) -> &gpio_cdev::errors::Error {
        &self.err
    }
}

impl From<gpio_cdev::errors::Error> for CdevPinError {
    fn from(err: gpio_cdev::errors::Error) -> Self {
        Self { err }
    }
}

impl fmt::Display for CdevPinError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.err)
    }
}

impl std::error::Error for CdevPinError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(&self.err)
    }
}

impl embedded_hal::digital::Error for CdevPinError {
    fn kind(&self) -> embedded_hal::digital::ErrorKind {
        use embedded_hal::digital::ErrorKind;
        ErrorKind::Other
    }
}

impl embedded_hal::digital::ErrorType for CdevPin {
    type Error = CdevPinError;
}

impl embedded_hal::digital::OutputPin for CdevPin {
    fn set_low(&mut self) -> Result<(), Self::Error> {
        self.0
            .set_value(state_to_value(
                embedded_hal::digital::PinState::Low,
                self.1.is_active_low(),
            ))
            .map_err(CdevPinError::from)
    }

    fn set_high(&mut self) -> Result<(), Self::Error> {
        self.0
            .set_value(state_to_value(
                embedded_hal::digital::PinState::High,
                self.1.is_active_low(),
            ))
            .map_err(CdevPinError::from)
    }
}

impl embedded_hal::digital::InputPin for CdevPin {
    fn is_high(&mut self) -> Result<bool, Self::Error> {
        self.0
            .get_value()
            .map(|val| {
                val == state_to_value(
                    embedded_hal::digital::PinState::High,
                    self.1.is_active_low(),
                )
            })
            .map_err(CdevPinError::from)
    }

    fn is_low(&mut self) -> Result<bool, Self::Error> {
        self.is_high().map(|val| !val)
    }
}

impl core::ops::Deref for CdevPin {
    type Target = gpio_cdev::LineHandle;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl core::ops::DerefMut for CdevPin {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}


================================================
FILE: src/delay.rs
================================================
//! Implementation of [`embedded-hal`] delay traits
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use embedded_hal::delay::DelayNs;
use std::thread;
use std::time::Duration;

/// Empty struct that provides delay functionality on top of `thread::sleep`,
/// and `tokio::time::sleep` if the `async-tokio` feature is enabled.
pub struct Delay;

impl DelayNs for Delay {
    fn delay_ns(&mut self, n: u32) {
        thread::sleep(Duration::from_nanos(n.into()));
    }

    fn delay_us(&mut self, n: u32) {
        thread::sleep(Duration::from_micros(n.into()));
    }

    fn delay_ms(&mut self, n: u32) {
        thread::sleep(Duration::from_millis(n.into()));
    }
}

#[cfg(feature = "async-tokio")]
impl embedded_hal_async::delay::DelayNs for Delay {
    async fn delay_ns(&mut self, n: u32) {
        tokio::time::sleep(Duration::from_nanos(n.into())).await;
    }

    async fn delay_us(&mut self, n: u32) {
        tokio::time::sleep(Duration::from_micros(n.into())).await;
    }

    async fn delay_ms(&mut self, n: u32) {
        tokio::time::sleep(Duration::from_millis(n.into())).await;
    }
}


================================================
FILE: src/i2c.rs
================================================
//! Implementation of [`embedded-hal`] I2C traits
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use std::fmt;
use std::ops;
use std::path::{Path, PathBuf};

use embedded_hal::i2c::NoAcknowledgeSource;

/// Newtype around [`i2cdev::linux::LinuxI2CDevice`] that implements the `embedded-hal` traits
///
/// [`i2cdev::linux::LinuxI2CDevice`]: https://docs.rs/i2cdev/0.5.0/i2cdev/linux/struct.LinuxI2CDevice.html
pub struct I2cdev {
    inner: i2cdev::linux::LinuxI2CDevice,
    path: PathBuf,
    address: Option<u16>,
}

impl I2cdev {
    /// See [`i2cdev::linux::LinuxI2CDevice::new`][0] for details.
    ///
    /// [0]: https://docs.rs/i2cdev/0.5.0/i2cdev/linux/struct.LinuxI2CDevice.html#method.new
    pub fn new<P>(path: P) -> Result<Self, i2cdev::linux::LinuxI2CError>
    where
        P: AsRef<Path>,
    {
        let dev = I2cdev {
            path: path.as_ref().to_path_buf(),
            inner: i2cdev::linux::LinuxI2CDevice::new(path, 0)?,
            address: None,
        };
        Ok(dev)
    }

    fn set_address(&mut self, address: u16) -> Result<(), i2cdev::linux::LinuxI2CError> {
        if self.address != Some(address) {
            self.inner = i2cdev::linux::LinuxI2CDevice::new(&self.path, address)?;
            self.address = Some(address);
        }
        Ok(())
    }
}

impl ops::Deref for I2cdev {
    type Target = i2cdev::linux::LinuxI2CDevice;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

impl ops::DerefMut for I2cdev {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.inner
    }
}

mod embedded_hal_impl {
    use super::*;
    use embedded_hal::i2c::ErrorType;
    use embedded_hal::i2c::{I2c, Operation as I2cOperation, SevenBitAddress, TenBitAddress};
    use i2cdev::core::{I2CMessage, I2CTransfer};
    use i2cdev::linux::LinuxI2CMessage;
    impl ErrorType for I2cdev {
        type Error = I2CError;
    }

    impl I2c<TenBitAddress> for I2cdev {
        fn transaction(
            &mut self,
            address: u16,
            operations: &mut [I2cOperation],
        ) -> Result<(), Self::Error> {
            // Map operations from generic to linux objects
            let mut messages: Vec<_> = operations
                .as_mut()
                .iter_mut()
                .map(|a| match a {
                    I2cOperation::Write(w) => LinuxI2CMessage::write(w),
                    I2cOperation::Read(r) => LinuxI2CMessage::read(r),
                })
                .collect();

            self.set_address(address)?;
            self.inner
                .transfer(&mut messages)
                .map(drop)
                .map_err(|err| I2CError { err })
        }
    }

    impl I2c<SevenBitAddress> for I2cdev {
        fn transaction(
            &mut self,
            address: u8,
            operations: &mut [I2cOperation],
        ) -> Result<(), Self::Error> {
            I2c::<TenBitAddress>::transaction(self, u16::from(address), operations)
        }
    }
}

/// Error type wrapping [LinuxI2CError](i2cdev::linux::LinuxI2CError) to implement [embedded_hal::i2c::ErrorKind]
#[derive(Debug)]
pub struct I2CError {
    err: i2cdev::linux::LinuxI2CError,
}

impl I2CError {
    /// Fetch inner (concrete) [`LinuxI2CError`]
    pub fn inner(&self) -> &i2cdev::linux::LinuxI2CError {
        &self.err
    }
}

impl From<i2cdev::linux::LinuxI2CError> for I2CError {
    fn from(err: i2cdev::linux::LinuxI2CError) -> Self {
        Self { err }
    }
}

impl fmt::Display for I2CError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.err)
    }
}

impl std::error::Error for I2CError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(&self.err)
    }
}

impl embedded_hal::i2c::Error for I2CError {
    fn kind(&self) -> embedded_hal::i2c::ErrorKind {
        use embedded_hal::i2c::ErrorKind;
        use nix::errno::Errno::*;

        let errno = match &self.err {
            i2cdev::linux::LinuxI2CError::Errno(e) => nix::Error::from_i32(*e),
            i2cdev::linux::LinuxI2CError::Io(e) => match e.raw_os_error() {
                Some(r) => nix::Error::from_i32(r),
                None => return ErrorKind::Other,
            },
        };

        // https://www.kernel.org/doc/html/latest/i2c/fault-codes.html
        match errno {
            EBUSY | EINVAL | EIO => ErrorKind::Bus,
            EAGAIN => ErrorKind::ArbitrationLoss,
            ENODEV => ErrorKind::NoAcknowledge(NoAcknowledgeSource::Data),
            ENXIO => ErrorKind::NoAcknowledge(NoAcknowledgeSource::Address),
            _ => ErrorKind::Other,
        }
    }
}


================================================
FILE: src/lib.rs
================================================
//! Implementation of [`embedded-hal`] traits for Linux devices
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal
//!
//! # Drivers
//!
//! This crate lets you use a bunch of platform agnostic drivers that are based on the
//! `embedded-hal` traits. You can find them on crates.io by [searching for the embedded-hal
//! keyword][0].
//!
//! [0]: https://crates.io/keywords/embedded-hal

#![deny(missing_docs)]

#[cfg(feature = "i2c")]
pub use i2cdev;
pub use nb;
#[cfg(feature = "serial")]
pub use serialport;
#[cfg(feature = "spi")]
pub use spidev;

#[cfg(feature = "gpio_sysfs")]
pub use sysfs_gpio;

#[cfg(feature = "gpio_cdev")]
pub use gpio_cdev;
#[cfg(feature = "gpio_sysfs")]
/// Sysfs Pin wrapper module
mod sysfs_pin;

#[cfg(feature = "gpio_cdev")]
/// Cdev Pin wrapper module
mod cdev_pin;

#[cfg(feature = "gpio_cdev")]
/// Cdev pin re-export
pub use cdev_pin::{CdevPin, CdevPinError};

#[cfg(feature = "gpio_sysfs")]
/// Sysfs pin re-export
pub use sysfs_pin::{SysfsPin, SysfsPinError};

mod delay;
#[cfg(feature = "i2c")]
mod i2c;
#[cfg(feature = "serial")]
mod serial;
#[cfg(feature = "spi")]
mod spi;
mod timer;

pub use crate::delay::Delay;
#[cfg(feature = "i2c")]
pub use crate::i2c::{I2CError, I2cdev};
#[cfg(feature = "serial")]
pub use crate::serial::{Serial, SerialError};
#[cfg(feature = "spi")]
pub use crate::spi::{SPIError, SpidevBus, SpidevDevice};
pub use crate::timer::{CountDown, Periodic, SysTimer};


================================================
FILE: src/serial.rs
================================================
//! Implementation of [`embedded-hal`] serial traits
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use serialport::{SerialPortBuilder, TTYPort};
use std::fmt;
use std::io::{ErrorKind as IoErrorKind, Read, Write};

/// Newtype around [`serialport::TTYPort`] that implements
/// the `embedded-hal` traits.
pub struct Serial(pub TTYPort);

impl Serial {
    /// Open a `serialport::TTYPort` by providing the port path and baud rate
    pub fn open(path: String, baud_rate: u32) -> Result<Serial, serialport::Error> {
        Ok(Serial(serialport::new(path, baud_rate).open_native()?))
    }

    /// Open a `serialport::TTYPort` by providing `serialport::SerialPortBuilder`
    pub fn open_from_builder(builder: SerialPortBuilder) -> Result<Serial, serialport::Error> {
        Ok(Serial(builder.open_native()?))
    }
}

/// Helper to convert std::io::Error to the nb::Error
fn translate_io_errors(err: std::io::Error) -> nb::Error<SerialError> {
    match err.kind() {
        IoErrorKind::WouldBlock | IoErrorKind::TimedOut | IoErrorKind::Interrupted => {
            nb::Error::WouldBlock
        }
        err => nb::Error::Other(SerialError { err }),
    }
}

impl embedded_hal_nb::serial::ErrorType for Serial {
    type Error = SerialError;
}

impl embedded_hal_nb::serial::Read<u8> for Serial {
    fn read(&mut self) -> nb::Result<u8, Self::Error> {
        let mut buffer = [0; 1];
        let bytes_read = self.0.read(&mut buffer).map_err(translate_io_errors)?;
        if bytes_read == 1 {
            Ok(buffer[0])
        } else {
            Err(nb::Error::WouldBlock)
        }
    }
}

impl embedded_hal_nb::serial::Write<u8> for Serial {
    fn write(&mut self, word: u8) -> nb::Result<(), Self::Error> {
        self.0.write(&[word]).map_err(translate_io_errors)?;
        Ok(())
    }

    fn flush(&mut self) -> nb::Result<(), Self::Error> {
        self.0.flush().map_err(translate_io_errors)
    }
}

/// Error type wrapping [io::ErrorKind](IoErrorKind) to implement [embedded_hal::serial::ErrorKind]
#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub struct SerialError {
    err: IoErrorKind,
}

impl SerialError {
    /// Fetch inner (concrete) [`IoErrorKind`]
    pub fn inner(&self) -> &IoErrorKind {
        &self.err
    }
}

impl fmt::Display for SerialError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.err)
    }
}

impl std::error::Error for SerialError {}

impl embedded_hal_nb::serial::Error for SerialError {
    #[allow(clippy::match_single_binding)]
    fn kind(&self) -> embedded_hal_nb::serial::ErrorKind {
        use embedded_hal_nb::serial::ErrorKind::*;
        // TODO: match any errors here if we can find any that are relevant
        Other
    }
}

#[cfg(test)]
mod test {
    use embedded_hal_nb::serial::{Read, Write};
    use std::io::{Read as IoRead, Write as IoWrite};

    use super::*;

    fn create_pty_and_serial() -> (std::fs::File, Serial) {
        let (master, _slave, name) =
            openpty::openpty(None, None, None).expect("Creating pty failed");
        let serial = Serial::open(name, 9600).expect("Creating TTYPort failed");
        (master, serial)
    }

    #[test]
    fn create_serial_from_builder() {
        let (_master, _slave, name) =
            openpty::openpty(None, None, None).expect("Creating pty failed");
        let builder = serialport::new(name, 9600);
        let _serial = Serial::open_from_builder(builder).expect("Creating TTYPort failed");
    }

    #[test]
    fn test_empty_read() {
        let (mut _master, mut serial) = create_pty_and_serial();
        assert_eq!(Err(nb::Error::WouldBlock), serial.read());
    }

    #[test]
    fn test_read() {
        let (mut master, mut serial) = create_pty_and_serial();
        master.write_all(&[1]).expect("Write failed");
        assert_eq!(Ok(1), serial.read());
    }

    #[test]
    fn test_write() {
        let (mut master, mut serial) = create_pty_and_serial();
        serial.write(2).expect("Write failed");
        let mut buf = [0; 2];
        assert_eq!(1, master.read(&mut buf).unwrap());
        assert_eq!(buf, [2, 0]);
    }
}


================================================
FILE: src/spi.rs
================================================
//! Implementation of [`embedded-hal`] SPI traits
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal
//!

use std::cmp::Ordering;
use std::fmt;
use std::io;
use std::ops;
use std::path::Path;

/// Spidev wrapper providing the embedded-hal [`SpiDevice`] trait.
///
/// Use this struct when you want a single spidev device, using a Linux-managed CS (chip-select) pin,
/// which is already defined in your device tree. Linux will handle sharing the bus
/// between different SPI devices, even between different processes.
///
/// You get an object that implements [`SpiDevice`], which is what most drivers require,
/// but does not implement [`SpiBus`]. In some rare cases, you may require [`SpiBus`]
/// instead; for that refer to [`SpidevBus`] below. You may also want to use [`SpiBus`]
/// if you want to handle all the CS pins yourself using GPIO.
///
/// This struct wraps a [`spidev::Spidev`] struct, so it can be constructed directly
/// and the inner struct accessed if needed, for example to (re)configure the SPI settings.
///
/// Note that [delay operations] on this device are capped to 65535 microseconds.
///
/// [`SpiDevice`]: embedded_hal::spi::SpiDevice
/// [`SpiBus`]: embedded_hal::spi::SpiBus
/// [`spidev::Spidev`]: spidev::Spidev
/// [delay operations]: embedded_hal::spi::Operation::DelayUs
pub struct SpidevDevice(pub spidev::Spidev);

/// Spidev wrapper providing the embedded-hal [`SpiBus`] trait.
///
/// Use this struct when you require direct access to the underlying SPI bus, for
/// example when you want to use GPIOs as software-controlled CS (chip-select) pins to share the
/// bus with multiple devices, or because a driver requires the entire bus (for
/// example to drive smart LEDs).
///
/// Do not use this struct if you're accessing SPI devices that already appear in your
/// device tree; you will not be able to drive CS pins that are already used by `spidev`
/// as GPIOs. Instead use [`SpidevDevice`].
///
/// This struct must still be created from a [`spidev::Spidev`] device, but there are two
/// important notes:
///
/// 1. The CS pin associated with this `spidev` device will be driven whenever any device accesses
///    this bus, so it should be an unconnected or unused pin.
/// 2. No other `spidev` device on the same bus may be used as long as this `SpidevBus` exists,
///    as Linux will _not_ do anything to ensure this bus has exclusive access.
///
/// It is recommended to use a dummy `spidev` device associated with an unused CS pin, and then use
/// regular GPIOs as CS pins if required. If you are planning to share this bus using GPIOs, the
/// [`embedded-hal-bus`] crate may be of interest.
///
/// If necessary, you can [configure] the underlying [`spidev::Spidev`] instance with the
/// [`SPI_NO_CS`] flag set to prevent any CS pin activity.
///
/// [`SpiDevice`]: embedded_hal::spi::SpiDevice
/// [`SpiBus`]: embedded_hal::spi::SpiBus
/// [`embedded-hal-bus`]: https://docs.rs/embedded-hal-bus/
/// [`spidev::Spidev`]: spidev::Spidev
/// [delay operations]: embedded_hal::spi::Operation::DelayUs
/// [configure]: spidev::Spidev::configure
/// [`SPI_NO_CS`]: spidev::SpiModeFlags::SPI_NO_CS
pub struct SpidevBus(pub spidev::Spidev);

impl SpidevDevice {
    /// See [`spidev::Spidev::open`] for details.
    ///
    /// The provided `path` is for the specific device you wish to access.
    /// Access to the bus is shared with other devices via the Linux kernel.
    pub fn open<P>(path: P) -> Result<Self, SPIError>
    where
        P: AsRef<Path>,
    {
        spidev::Spidev::open(path)
            .map(SpidevDevice)
            .map_err(|e| e.into())
    }
}

impl SpidevBus {
    /// See [`spidev::Spidev::open`] for details.
    ///
    /// The provided `path` must be the _only_ device in use on its bus,
    /// and note its own CS pin will be asserted for all device access,
    /// so the path should be to a dummy device used only to access
    /// the underlying bus.
    pub fn open<P>(path: P) -> Result<Self, SPIError>
    where
        P: AsRef<Path>,
    {
        spidev::Spidev::open(path)
            .map(SpidevBus)
            .map_err(|e| e.into())
    }
}

impl ops::Deref for SpidevDevice {
    type Target = spidev::Spidev;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl ops::DerefMut for SpidevDevice {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl ops::Deref for SpidevBus {
    type Target = spidev::Spidev;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl ops::DerefMut for SpidevBus {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

mod embedded_hal_impl {
    use super::*;
    use embedded_hal::spi::ErrorType;
    use embedded_hal::spi::{Operation as SpiOperation, SpiBus, SpiDevice};
    use spidev::SpidevTransfer;
    use std::convert::TryInto;
    use std::io::{Read, Write};

    impl ErrorType for SpidevDevice {
        type Error = SPIError;
    }

    impl ErrorType for SpidevBus {
        type Error = SPIError;
    }

    impl SpiBus<u8> for SpidevBus {
        fn read(&mut self, words: &mut [u8]) -> Result<(), Self::Error> {
            self.0.read_exact(words).map_err(|err| SPIError { err })
        }

        fn write(&mut self, words: &[u8]) -> Result<(), Self::Error> {
            self.0.write_all(words).map_err(|err| SPIError { err })
        }

        fn transfer(&mut self, read: &mut [u8], write: &[u8]) -> Result<(), Self::Error> {
            let read_len = read.len();
            match read_len.cmp(&write.len()) {
                Ordering::Less => self.0.transfer_multiple(&mut [
                    SpidevTransfer::read_write(&write[..read_len], read),
                    SpidevTransfer::write(&write[read_len..]),
                ]),
                Ordering::Equal => self
                    .0
                    .transfer(&mut SpidevTransfer::read_write(write, read)),
                Ordering::Greater => {
                    let (read1, read2) = read.split_at_mut(write.len());
                    self.0.transfer_multiple(&mut [
                        SpidevTransfer::read_write(write, read1),
                        SpidevTransfer::read(read2),
                    ])
                }
            }
            .map_err(|err| SPIError { err })
        }

        fn transfer_in_place(&mut self, words: &mut [u8]) -> Result<(), Self::Error> {
            self.0
                .transfer(&mut SpidevTransfer::read_write_in_place(words))
                .map_err(|err| SPIError { err })
        }

        fn flush(&mut self) -> Result<(), Self::Error> {
            self.0.flush().map_err(|err| SPIError { err })
        }
    }

    impl SpiDevice for SpidevDevice {
        /// Perform a transaction against the device. [Read more][transaction]
        ///
        /// [Delay operations][delay] are capped to 65535 microseconds.
        ///
        /// [transaction]: SpiDevice::transaction
        /// [delay]: SpiOperation::DelayUs
        fn transaction(
            &mut self,
            operations: &mut [SpiOperation<'_, u8>],
        ) -> Result<(), Self::Error> {
            let mut transfers = Vec::with_capacity(operations.len());
            for op in operations {
                match op {
                    SpiOperation::Read(buf) => transfers.push(SpidevTransfer::read(buf)),
                    SpiOperation::Write(buf) => transfers.push(SpidevTransfer::write(buf)),
                    SpiOperation::Transfer(read, write) => match read.len().cmp(&write.len()) {
                        Ordering::Less => {
                            let n = read.len();
                            transfers.push(SpidevTransfer::read_write(&write[..n], read));
                            transfers.push(SpidevTransfer::write(&write[n..]));
                        }
                        Ordering::Equal => transfers.push(SpidevTransfer::read_write(write, read)),
                        Ordering::Greater => {
                            let (read1, read2) = read.split_at_mut(write.len());
                            transfers.push(SpidevTransfer::read_write(write, read1));
                            transfers.push(SpidevTransfer::read(read2));
                        }
                    },
                    SpiOperation::TransferInPlace(buf) => {
                        transfers.push(SpidevTransfer::read_write_in_place(buf));
                    }
                    SpiOperation::DelayNs(ns) => {
                        let us = {
                            if *ns == 0 {
                                0
                            } else {
                                let us = *ns / 1000;
                                if us == 0 {
                                    1
                                } else {
                                    (us).try_into().unwrap_or(u16::MAX)
                                }
                            }
                        };
                        transfers.push(SpidevTransfer::delay(us));
                    }
                }
            }
            self.0
                .transfer_multiple(&mut transfers)
                .map_err(|err| SPIError { err })?;
            self.flush()?;
            Ok(())
        }
    }
}

/// Error type wrapping [io::Error](io::Error) to implement [embedded_hal::spi::ErrorKind]
#[derive(Debug)]
pub struct SPIError {
    err: io::Error,
}

impl SPIError {
    /// Fetch inner (concrete) [`LinuxI2CError`]
    pub fn inner(&self) -> &io::Error {
        &self.err
    }
}

impl From<io::Error> for SPIError {
    fn from(err: io::Error) -> Self {
        Self { err }
    }
}

impl embedded_hal::spi::Error for SPIError {
    #[allow(clippy::match_single_binding)]
    fn kind(&self) -> embedded_hal::spi::ErrorKind {
        use embedded_hal::spi::ErrorKind;
        // TODO: match any errors here if we can find any that are relevant
        ErrorKind::Other
    }
}

impl fmt::Display for SPIError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.err)
    }
}

impl std::error::Error for SPIError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(&self.err)
    }
}


================================================
FILE: src/sysfs_pin.rs
================================================
//! Implementation of [`embedded-hal`] digital input/output traits using a Linux Sysfs pin
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use std::fmt;
use std::path::Path;

/// Newtype around [`sysfs_gpio::Pin`] that implements the `embedded-hal` traits
///
/// [`sysfs_gpio::Pin`]: https://docs.rs/sysfs_gpio/0.6.0/sysfs_gpio/struct.Pin.html
pub struct SysfsPin(pub sysfs_gpio::Pin);

impl SysfsPin {
    /// See [`sysfs_gpio::Pin::new`][0] for details.
    ///
    /// [0]: https://docs.rs/sysfs_gpio/0.6.0/sysfs_gpio/struct.Pin.html#method.new
    pub fn new(pin_num: u64) -> Self {
        SysfsPin(sysfs_gpio::Pin::new(pin_num))
    }

    /// See [`sysfs_gpio::Pin::from_path`][0] for details.
    ///
    /// [0]: https://docs.rs/sysfs_gpio/0.6.0/sysfs_gpio/struct.Pin.html#method.from_path
    pub fn from_path<P>(path: P) -> sysfs_gpio::Result<Self>
    where
        P: AsRef<Path>,
    {
        sysfs_gpio::Pin::from_path(path).map(SysfsPin)
    }

    /// Convert this pin to an input pin
    pub fn into_input_pin(self) -> Result<SysfsPin, sysfs_gpio::Error> {
        self.set_direction(sysfs_gpio::Direction::In)?;
        Ok(self)
    }

    /// Convert this pin to an output pin
    pub fn into_output_pin(
        self,
        state: embedded_hal::digital::PinState,
    ) -> Result<SysfsPin, sysfs_gpio::Error> {
        self.set_direction(match state {
            embedded_hal::digital::PinState::High => sysfs_gpio::Direction::High,
            embedded_hal::digital::PinState::Low => sysfs_gpio::Direction::Low,
        })?;
        Ok(self)
    }
}

/// Error type wrapping [sysfs_gpio::Error](sysfs_gpio::Error) to implement [embedded_hal::digital::Error]
#[derive(Debug)]
pub struct SysfsPinError {
    err: sysfs_gpio::Error,
}

impl SysfsPinError {
    /// Fetch inner (concrete) [`sysfs_gpio::Error`]
    pub fn inner(&self) -> &sysfs_gpio::Error {
        &self.err
    }
}

impl From<sysfs_gpio::Error> for SysfsPinError {
    fn from(err: sysfs_gpio::Error) -> Self {
        Self { err }
    }
}

impl fmt::Display for SysfsPinError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.err)
    }
}

impl std::error::Error for SysfsPinError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        Some(&self.err)
    }
}

impl embedded_hal::digital::Error for SysfsPinError {
    fn kind(&self) -> embedded_hal::digital::ErrorKind {
        use embedded_hal::digital::ErrorKind;
        ErrorKind::Other
    }
}

impl embedded_hal::digital::ErrorType for SysfsPin {
    type Error = SysfsPinError;
}

impl embedded_hal::digital::OutputPin for SysfsPin {
    fn set_low(&mut self) -> Result<(), Self::Error> {
        if self.0.get_active_low().map_err(SysfsPinError::from)? {
            self.0.set_value(1).map_err(SysfsPinError::from)
        } else {
            self.0.set_value(0).map_err(SysfsPinError::from)
        }
    }

    fn set_high(&mut self) -> Result<(), Self::Error> {
        if self.0.get_active_low().map_err(SysfsPinError::from)? {
            self.0.set_value(0).map_err(SysfsPinError::from)
        } else {
            self.0.set_value(1).map_err(SysfsPinError::from)
        }
    }
}

impl embedded_hal::digital::InputPin for SysfsPin {
    fn is_high(&mut self) -> Result<bool, Self::Error> {
        if !self.0.get_active_low().map_err(SysfsPinError::from)? {
            self.0
                .get_value()
                .map(|val| val != 0)
                .map_err(SysfsPinError::from)
        } else {
            self.0
                .get_value()
                .map(|val| val == 0)
                .map_err(SysfsPinError::from)
        }
    }

    fn is_low(&mut self) -> Result<bool, Self::Error> {
        self.is_high().map(|val| !val).map_err(SysfsPinError::from)
    }
}

impl core::ops::Deref for SysfsPin {
    type Target = sysfs_gpio::Pin;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl core::ops::DerefMut for SysfsPin {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}


================================================
FILE: src/timer.rs
================================================
//! Implementation of [`embedded-hal`] timer traits
//!
//! [`embedded-hal`]: https://docs.rs/embedded-hal

use core::convert::Infallible;
use std::time::{Duration, Instant};

/// Marker trait that indicates that a timer is periodic
pub trait Periodic {}

/// A count down timer
///
/// Note that this is borrowed from `embedded-hal` 0.2.x and will be in use until the `1.x` version provides one.
///
/// # Contract
///
/// - `self.start(count); block!(self.wait());` MUST block for AT LEAST the time specified by
///   `count`.
///
/// *Note* that the implementer doesn't necessarily have to be a *downcounting* timer; it could also
/// be an *upcounting* timer as long as the above contract is upheld.
///
/// # Examples
///
/// You can use this timer to create delays
///
/// ```
/// use std::time::Duration;
/// use nb::block;
/// use linux_embedded_hal::{CountDown, SysTimer};
///
/// fn main() {
///     let mut led: Led = {
///         // ..
/// #       Led
///     };
///     let mut timer = SysTimer::new();
///
///     Led.on();
///     timer.start(Duration::from_millis(1000)).unwrap();
///     block!(timer.wait()); // blocks for 1 second
///     Led.off();
/// }
///
/// # use core::convert::Infallible;
/// # struct Seconds(u32);
/// # trait U32Ext { fn s(self) -> Seconds; }
/// # impl U32Ext for u32 { fn s(self) -> Seconds { Seconds(self) } }
/// # struct Led;
/// # impl Led {
/// #     pub fn off(&mut self) {}
/// #     pub fn on(&mut self) {}
/// # }
/// ```
pub trait CountDown {
    /// An enumeration of `CountDown` errors.
    ///
    /// For infallible implementations, will be `Infallible`
    type Error: core::fmt::Debug;

    /// The unit of time used by this timer
    type Time;

    /// Starts a new count down
    fn start<T>(&mut self, count: T) -> Result<(), Self::Error>
    where
        T: Into<Self::Time>;

    /// Non-blockingly "waits" until the count down finishes
    ///
    /// # Contract
    ///
    /// - If `Self: Periodic`, the timer will start a new count down right after the last one
    ///   finishes.
    /// - Otherwise the behavior of calling `wait` after the last call returned `Ok` is UNSPECIFIED.
    ///   Implementers are suggested to panic on this scenario to signal a programmer error.
    fn wait(&mut self) -> nb::Result<(), Self::Error>;
}

impl<T: CountDown> CountDown for &mut T {
    type Error = T::Error;

    type Time = T::Time;

    fn start<TIME>(&mut self, count: TIME) -> Result<(), Self::Error>
    where
        TIME: Into<Self::Time>,
    {
        T::start(self, count)
    }

    fn wait(&mut self) -> nb::Result<(), Self::Error> {
        T::wait(self)
    }
}

/// A periodic timer based on [`std::time::Instant`][instant], which is a
/// monotonically nondecreasing clock.
///
/// [instant]: https://doc.rust-lang.org/std/time/struct.Instant.html
pub struct SysTimer {
    start: Instant,
    duration: Duration,
}

impl SysTimer {
    /// Create a new timer instance.
    ///
    /// The `duration` will be initialized to 0, so make sure to call `start`
    /// with your desired timer duration before calling `wait`.
    pub fn new() -> SysTimer {
        SysTimer {
            start: Instant::now(),
            duration: Duration::from_millis(0),
        }
    }
}

impl Default for SysTimer {
    fn default() -> SysTimer {
        SysTimer::new()
    }
}

impl CountDown for SysTimer {
    type Error = Infallible;
    type Time = Duration;

    fn start<T>(&mut self, count: T) -> Result<(), Self::Error>
    where
        T: Into<Self::Time>,
    {
        self.start = Instant::now();
        self.duration = count.into();
        Ok(())
    }

    fn wait(&mut self) -> nb::Result<(), Self::Error> {
        if (Instant::now() - self.start) >= self.duration {
            // Restart the timer to fulfill the contract by `Periodic`
            self.start = Instant::now();
            Ok(())
        } else {
            Err(nb::Error::WouldBlock)
        }
    }
}

impl Periodic for SysTimer {}

#[cfg(test)]
mod tests {
    use super::*;

    /// Ensure that a 100 ms delay takes at least 100 ms,
    /// but not longer than 500 ms.
    #[test]
    fn test_delay() {
        let mut timer = SysTimer::new();
        let before = Instant::now();
        timer.start(Duration::from_millis(100)).unwrap();
        nb::block!(timer.wait()).unwrap();
        let after = Instant::now();
        let duration_ms = (after - before).as_millis();
        assert!(duration_ms >= 100);
        assert!(duration_ms < 500);
    }

    /// Ensure that the timer is periodic.
    #[test]
    fn test_periodic() {
        let mut timer = SysTimer::new();
        let before = Instant::now();
        timer.start(Duration::from_millis(100)).unwrap();
        nb::block!(timer.wait()).unwrap();
        let after1 = Instant::now();
        let duration_ms_1 = (after1 - before).as_millis();
        assert!(duration_ms_1 >= 100);
        assert!(duration_ms_1 < 500);
        nb::block!(timer.wait()).unwrap();
        let after2 = Instant::now();
        let duration_ms_2 = (after2 - after1).as_millis();
        assert!(duration_ms_2 >= 100);
        assert!(duration_ms_2 < 500);
    }
}