Add transactional traits for SPI and I2C

src/blocking/i2c.rs

@@ -127,3 +127,26 @@ pub trait WriteIterRead {
     where
         B: IntoIterator<Item = u8>;
 }
+
+/// Operation for transactional I2C trait
+///
+/// This allows composition of I2C operations into a single bus transaction
+#[cfg(feature = "unproven")]
+#[derive(Debug, PartialEq)]
+pub enum Operation<'a> {
+    /// Read data into the provided buffer
+    Read(&'a mut [u8]),
+    /// Write data from the provided buffer
+    Write(&'a [u8]),
+}
+
+/// Transactional trait allows multiple actions to be executed
+/// as part of a single I2C transaction
+#[cfg(feature = "unproven")]
+pub trait Transactional {
+    /// Associated error type
+    type Error;
+
+    /// Execute the provided actions against the provided I2C address
+    fn exec<'a>(&mut self, address: u8, operations: &mut[Operation<'a>]) -> Result<(), Self::Error>;
+}

src/blocking/spi.rs

@@ -104,3 +104,26 @@ pub mod write_iter {
         }
     }
 }
+
+/// Operation for transactional SPI trait
+///
+/// This allows composition of SPI operations into a single bus transaction
+#[cfg(feature = "unproven")]
+#[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
+    WriteRead(&'a mut [W]),
+}
+
+/// Transactional trait allows multiple actions to be executed
+/// as part of a single SPI transaction
+#[cfg(feature = "unproven")]
+pub trait Transactional<W: 'static> {
+    /// Associated error type
+    type Error;
+
+    /// Execute the provided transactions
+    fn exec<'a>(&mut self, operations: &mut [Operation<'a, W>]) -> Result<(), Self::Error>;
+}