spi: add Read and separate-buffers Transfer

CHANGELOG.md

@@ -31,6 +31,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
  dynamically.
 - Added `Debug` to all spi mode types.
 - Add impls of all traits for references (`&T` or `&mut T` depending on the trait) when `T` implements the trait.
+- SPI: Added blocking `Read` trait and `Read` transactional operation
+- SPI: Added blocking `Transfer` trait with separate buffers (single-buffer `Transfer` has been renamed `TransferInplace`)
 
 ### Changed
 - Swap PWM channel arguments to references

src/spi/blocking.rs

@@ -4,15 +4,41 @@
 //! traits. To save boilerplate when that's the case a `Default` marker trait may be provided.
 //! Implementing that marker trait will opt in your type into a blanket implementation.
 
-/// Blocking transfer
+/// Blocking transfer with separate buffers
 pub trait Transfer<W> {
  /// Error type
  type Error: crate::spi::Error;
 
+ /// Writes and reads simultaneously. `write` is written to the slave on MOSI and
+ /// words received on MISO are stored in `read`.
+ ///
+ /// It is allowed for `read` and `write` to have different lengths, even zero length.
+ /// The transfer runs for `max(read.len(), write.len())` words. If `read` is shorter,
+ /// incoming words after `read` has been filled will be discarded. If `write` is shorter,
+ /// the value of words sent in MOSI after all `write` has been sent is implementation-defined,
+ /// typically `0x00`, `0xFF`, or configurable.
+ fn transfer(&mut self, read: &mut [W], write: &[W]) -> Result<(), Self::Error>;
+}
+
+/// Blocking transfer with single buffer (in-place)
+pub trait TransferInplace<W> {
+ /// Error type
+ type Error: core::fmt::Debug;
+
  /// Writes and reads simultaneously. The contents of `words` are
  /// written to the slave, and the received words are stored into the same
  /// `words` buffer, overwriting it.
- fn transfer(&mut self, words: &mut [W]) -> Result<(), Self::Error>;
+ fn transfer_inplace(&mut self, words: &mut [W]) -> Result<(), Self::Error>;
+}
+
+/// Blocking read
+pub trait Read<W> {
+ /// Error type
+ type Error;
+
+ /// Reads `words` to the slave. The word value sent on MOSI during
+ /// reading is implementation-defined, typically `0x00`, `0xFF`, or configurable.
+ fn read(&mut self, words: &mut [W]) -> Result<(), Self::Error>;
 }
 
 impl<T: Transfer<W>, W> Transfer<W> for &mut T {
@@ -67,10 +93,14 @@ impl<T: WriteIter<W>, W> WriteIter<W> for &mut T {
 /// This allows composition of SPI operations into a single bus transaction
 #[derive(Debug, PartialEq)]
 pub enum Operation<'a, W: 'static> {
+ /// Read data into the provided buffer.
+ Read(&'a mut [W]),
  /// 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]),
+ Transfer(&'a mut [W], &'a [W]),
+ /// Write data out while reading data into the provided buffer
+ TransferInplace(&'a mut [W]),
 }
 
 /// Transactional trait allows multiple actions to be executed