1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157

//! 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,
        }
    }
}