From 1476c81c2e83d1b6bcee005a4dbe19ebee17f745 Mon Sep 17 00:00:00 2001
From: Gabriel Smith <ga29smith@gmail.com>
Date: Tue, 5 Oct 2021 19:36:22 -0400
Subject: [PATCH 1/2] i2c: Merge NoAcknowledgeData and NoAcknowledgeAddress
 into one variant

A source enum was added to indicate if the NACK was from an address or a
data byte. Some drivers may not be able to differentiate so they should
use `Unknown`.
---
 CHANGELOG.md |  5 +++++
 src/i2c.rs   | 38 ++++++++++++++++++++++++++++++++------
 2 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 145c9a223..c522c8386 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   implement these `Error` traits, which implies providing a conversion to a common
   set of error kinds. Generic drivers using these interfaces can then convert the errors
   to this common set to act upon them.
+- The `NoAcknowledgeAddress` and `NoAcknowledgeData` variants of the I2C `Error`
+  trait have been merged into `NoAcknowledge` with a `NoAcknowledgeSource` field
+  to differentiate between the two events. An additional `Unknown` variant is
+  provided in `NoAcknowledgeSource` for devices that can't differentiate between
+  the two events.
 
 ### Removed
 - Removed `DelayMs` in favor of `DelayUs` with `u32` as type for clarity.
diff --git a/src/i2c.rs b/src/i2c.rs
index 0dbda4256..f06c37355 100644
--- a/src/i2c.rs
+++ b/src/i2c.rs
@@ -123,16 +123,33 @@ pub enum ErrorKind {
     Bus,
     /// The arbitration was lost, e.g. electrical problems with the clock signal
     ArbitrationLoss,
-    /// The device did not acknowledge its address. The device may be missing.
-    NoAcknowledgeAddress,
-    /// The device did not acknowled the data. It may not be ready to process requests at the moment.
-    NoAcknowledgeData,
+    /// A bus operation was not acknowledged, e.g. due to the addressed device not
+    /// being available on the bus or the device not being ready to process requests
+    /// at the moment
+    NoAcknowledge(NoAcknowledgeSource),
     /// The peripheral receive buffer was overrun
     Overrun,
     /// A different error occurred. The original error may contain more information.
     Other,
 }
 
+/// I2C no acknowledge error source
+///
+/// In cases where it is possible, a device should indicate if a no acknowledge
+/// response was received to an address versus a no acknowledge to a data byte.
+/// Where it is not possible to differentiate, `Unknown` should be indicated.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub enum NoAcknowledgeSource {
+    /// The device did not acknowledge its address. The device may be missing.
+    Address,
+    /// The device did not acknowledge the data. It may not be ready to process
+    /// requests at the moment.
+    Data,
+    /// Either the device did not acknowledge its address or the data, but it is
+    /// unknown which.
+    Unknown,
+}
+
 impl Error for ErrorKind {
     fn kind(&self) -> ErrorKind {
         *self
@@ -144,8 +161,7 @@ impl core::fmt::Display for ErrorKind {
         match self {
             Self::Bus => write!(f, "Bus error occurred"),
             Self::ArbitrationLoss => write!(f, "The arbitration was lost"),
-            Self::NoAcknowledgeAddress => write!(f, "The device did not acknowledge its address"),
-            Self::NoAcknowledgeData => write!(f, "The device did not acknowledge the data"),
+            Self::NoAcknowledge(s) => s.fmt(f),
             Self::Overrun => write!(f, "The peripheral receive buffer was overrun"),
             Self::Other => write!(
                 f,
@@ -155,6 +171,16 @@ impl core::fmt::Display for ErrorKind {
     }
 }
 
+impl core::fmt::Display for NoAcknowledgeSource {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::Address => write!(f, "The device did not acknowledge its address"),
+            Self::Data => write!(f, "The device did not acknowledge the data"),
+            Self::Unknown => write!(f, "The device did not acknowledge its address or the data"),
+        }
+    }
+}
+
 /// Address mode (7-bit / 10-bit)
 ///
 /// Note: This trait is sealed and should not be implemented outside of this crate.

From c5d179917bca86a4d712800dd8f0c10417fdf1d5 Mon Sep 17 00:00:00 2001
From: Gabriel Smith <ga29smith@gmail.com>
Date: Tue, 5 Oct 2021 19:38:08 -0400
Subject: [PATCH 2/2] i2c: docs: Wrap a long line on ErrorKind::Bus

---
 src/i2c.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/i2c.rs b/src/i2c.rs
index f06c37355..6d50192e5 100644
--- a/src/i2c.rs
+++ b/src/i2c.rs
@@ -119,7 +119,8 @@ pub trait Error: core::fmt::Debug {
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
 #[non_exhaustive]
 pub enum ErrorKind {
-    /// Bus error occurred. e.g. A START or a STOP condition is detected and is not located after a multiple of 9 SCL clock pulses.
+    /// Bus error occurred. e.g. A START or a STOP condition is detected and is not
+    /// located after a multiple of 9 SCL clock pulses.
     Bus,
     /// The arbitration was lost, e.g. electrical problems with the clock signal
     ArbitrationLoss,