Merge #74

74: Update nix to 0.25, hide nix from public API. r=eldruin a=Erk-

Hiding nix from the public API will allow to update it in the future without causing a breaking change.

Co-authored-by: Valdemar Erk <valdemar@erk.dev>
Co-authored-by: Erk <Erk-@users.noreply.github.com>

Author: bors[bot]

CHANGELOG.md

@@ -8,6 +8,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+- Hide nix from the public api such that it can be updated without resulting in a breaking change.
+- Updated nix to version `0.25`.
 - Updated nix to version `0.24`; only use the `ioctl` feature.
 - Use `File.read_exact` instead of `File.read` in `LinuxI2CDevice.read` so that the buffer is filled.
 

Cargo.toml

@@ -18,7 +18,7 @@ Provides API for safe access to Linux i2c device interface.
 libc = "0.2"
 bitflags = "1.3"
 byteorder = "1"
-nix = { version = "0.24", default-features = false, features = ["ioctl"] }
+nix = { version = "0.25", default-features = false, features = ["ioctl"] }
 
 [dev-dependencies]
 docopt = "1"

src/linux.rs

@@ -36,15 +36,24 @@ pub struct LinuxI2CBus {
 /// Linux I2C errors
 #[derive(Debug)]
 pub enum LinuxI2CError {
-    /// OS error
-    Nix(nix::Error),
+    /// Errno from a failing `libc` call. Sourced  from [`nix`].
+    ///
+    /// To interpret this value [`nix::errno::from_i32`] should be used.
+    ///
+    /// The [`Error`] implementation will not return a source
+    /// for this variant, like the [`Error`] implementation of the underlying `nix` error.
+    ///
+    /// [`nix`]: https://docs.rs/nix/latest/nix/
+    /// [`nix::errno::from_i32`]: https://docs.rs/nix/latest/nix/errno/fn.from_i32.html
+    /// [`Error`]: https://doc.rust-lang.org/std/error/trait.Error.html
+    Errno(i32),
     /// Input/output error
     Io(io::Error),
 }
 
 impl From<nix::Error> for LinuxI2CError {
     fn from(e: nix::Error) -> Self {
-        LinuxI2CError::Nix(e)
+        LinuxI2CError::Errno(e as i32)
     }
 }
 
@@ -58,15 +67,18 @@ impl From<LinuxI2CError> for io::Error {
     fn from(e: LinuxI2CError) -> io::Error {
         match e {
             LinuxI2CError::Io(e) => e,
-            LinuxI2CError::Nix(e) => e.into(),
+            LinuxI2CError::Errno(e) => io::Error::from_raw_os_error(e),
         }
     }
 }
 
 impl fmt::Display for LinuxI2CError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
-            LinuxI2CError::Nix(ref e) => fmt::Display::fmt(e, f),
+            LinuxI2CError::Errno(e) => {
+                let error = nix::Error::from_i32(e);
+                fmt::Display::fmt(&error, f)
+            }
             LinuxI2CError::Io(ref e) => fmt::Display::fmt(e, f),
         }
     }
@@ -76,7 +88,7 @@ impl Error for LinuxI2CError {
     fn cause(&self) -> Option<&dyn Error> {
         match *self {
             LinuxI2CError::Io(ref e) => Some(e),
-            LinuxI2CError::Nix(ref e) => Some(e),
+            LinuxI2CError::Errno(_) => None,
         }
     }
 }