From fbff6472539c12a7864d37d22e1dca9194980e52 Mon Sep 17 00:00:00 2001
From: Ryan Kurte <ryankurte@gmail.com>
Date: Mon, 9 Mar 2020 21:54:28 +1300
Subject: [PATCH 1/3] Added transactional SPI interface See:
 https://github.com/rust-embedded/embedded-hal/pull/178 for work to get here

---
 src/blocking/spi.rs | 49 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/src/blocking/spi.rs b/src/blocking/spi.rs
index b1e81bb8a..58680dd0e 100644
--- a/src/blocking/spi.rs
+++ b/src/blocking/spi.rs
@@ -102,3 +102,52 @@ pub mod write_iter {
         }
     }
 }
+
+/// Operation for transactional SPI trait
+///
+/// This allows composition of SPI operations into a single bus transaction
+#[derive(Debug, PartialEq)]
+pub enum Operation<'a, W: 'static> {
+    /// Write data from the provided buffer, discarding read data
+    Write(&'a [W]),
+    /// Write data out while reading data into the provided buffer
+    Transfer(&'a mut [W]),
+}
+
+/// Transactional trait allows multiple actions to be executed
+/// as part of a single SPI transaction
+pub trait Transactional<W: 'static> {
+    /// Associated error type
+    type Error;
+
+    /// Execute the provided transactions
+    fn try_exec<'a>(&mut self, operations: &mut [Operation<'a, W>]) -> Result<(), Self::Error>;
+}
+
+/// Blocking transactional impl over spi::Write and spi::Transfer
+pub mod transactional {
+    use super::{Operation, Transfer, Write};
+
+    /// Default implementation of `blocking::spi::Transactional<W>` for implementers of
+    /// `spi::Write<W>` and `spi::Transfer<W>`
+    pub trait Default<W, E> {}
+
+    impl<W: 'static, E, S> super::Transactional<W> for S
+    where
+        S: self::Default<W, E> + Write<W, Error = E> + Transfer<W, Error = E>,
+        W: Copy + Clone,
+    {
+        type Error = E;
+
+        fn try_exec<'a>(&mut self, operations: &mut [super::Operation<'a, W>]) -> Result<(), E> {
+            for op in operations {
+                match op {
+                    Operation::Write(w) => self.try_write(w)?,
+                    Operation::Transfer(t) => self.try_transfer(t).map(|_| ())?,
+                }
+            }
+
+            Ok(())
+        }
+    }
+}

From db7b4f26e5bb60f7fe5166b6a42d4d23c11125dd Mon Sep 17 00:00:00 2001
From: ryan <ryan@kurte.nz>
Date: Thu, 25 Jun 2020 11:21:12 +1200
Subject: [PATCH 2/3] fixed default impl

---
 src/blocking/spi.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/blocking/spi.rs b/src/blocking/spi.rs
index 58680dd0e..b5a0ae211 100644
--- a/src/blocking/spi.rs
+++ b/src/blocking/spi.rs
@@ -130,11 +130,11 @@ pub mod transactional {
 
     /// Default implementation of `blocking::spi::Transactional<W>` for implementers of
     /// `spi::Write<W>` and `spi::Transfer<W>`
-    pub trait Default<W, E> {}
+    pub trait Default<W>: Write<W> + Transfer<W> {}
 
     impl<W: 'static, E, S> super::Transactional<W> for S
     where
-        S: self::Default<W, E> + Write<W, Error = E> + Transfer<W, Error = E>,
+        S: self::Default<W> + Write<W, Error=E> + Transfer<W, Error=E> ,
         W: Copy + Clone,
     {
         type Error = E;

From c66420be3c90989143d8a86665f1ed802ede40bb Mon Sep 17 00:00:00 2001
From: ryan <ryan@kurte.nz>
Date: Tue, 27 Oct 2020 11:58:55 +1300
Subject: [PATCH 3/3] apply cargo fmt

---
 src/blocking/spi.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/blocking/spi.rs b/src/blocking/spi.rs
index b5a0ae211..93fad65c1 100644
--- a/src/blocking/spi.rs
+++ b/src/blocking/spi.rs
@@ -134,7 +134,7 @@ pub mod transactional {
 
     impl<W: 'static, E, S> super::Transactional<W> for S
     where
-        S: self::Default<W> + Write<W, Error=E> + Transfer<W, Error=E> ,
+        S: self::Default<W> + Write<W, Error = E> + Transfer<W, Error = E>,
         W: Copy + Clone,
     {
         type Error = E;