Update embedded-hal and backport transactional SPI implementation

Author: eldruin

Cargo.toml

@@ -15,7 +15,7 @@ gpio_cdev = ["gpio-cdev"]
 default = [ "gpio_cdev", "gpio_sysfs" ]
 
 [dependencies]
-embedded-hal = { version = "0.2.3", features = ["unproven"] }
+embedded-hal = { version = "0.2.6", features = ["unproven"] }
 gpio-cdev = { version = "0.3", optional = true }
 sysfs_gpio = { version = "0.5", optional = true }
 

src/lib.rs

@@ -13,22 +13,19 @@
 #![deny(missing_docs)]
 
 extern crate cast;
-extern crate core;
 extern crate embedded_hal as hal;
 pub extern crate i2cdev;
-pub extern crate spidev;
-pub extern crate serial_unix;
-pub extern crate serial_core;
 pub extern crate nb;
-
+pub extern crate serial_core;
+pub extern crate serial_unix;
+pub extern crate spidev;
 
 #[cfg(feature = "gpio_sysfs")]
 pub extern crate sysfs_gpio;
 
 #[cfg(feature = "gpio_cdev")]
 pub extern crate gpio_cdev;
 
-
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 use std::time::Duration;
@@ -60,7 +57,6 @@ pub use cdev_pin::CdevPin;
 /// Sysfs pin re-export
 pub use sysfs_pin::SysfsPin;
 
-
 /// Empty struct that provides delay functionality on top of `thread::sleep`
 pub struct Delay;
 
@@ -118,7 +114,6 @@ impl hal::blocking::delay::DelayMs<u64> for Delay {
     }
 }
 
-
 /// Newtype around [`i2cdev::linux::LinuxI2CDevice`] that implements the `embedded-hal` traits
 ///
 /// [`i2cdev::linux::LinuxI2CDevice`]: https://docs.rs/i2cdev/0.3.1/i2cdev/linux/struct.LinuxI2CDevice.html
@@ -236,6 +231,39 @@ impl hal::blocking::spi::Write<u8> for Spidev {
     }
 }
 
+pub use hal::blocking::spi::Operation as SpiOperation;
+
+impl hal::blocking::spi::Transactional<u8> for Spidev {
+    type Error = io::Error;
+
+    fn exec<'a>(&mut self, operations: &mut [SpiOperation<'a, u8>]) -> Result<(), Self::Error> {
+        // Map types from generic to linux objects
+        let mut messages: Vec<_> = operations
+            .iter_mut()
+            .map(|a| {
+                match a {
+                    SpiOperation::Write(w) => SpidevTransfer::write(w),
+                    SpiOperation::Transfer(r) => {
+                        // Clone read to write pointer
+                        // SPIdev is okay with having w == r but this is tricky to achieve in safe rust
+                        let w = unsafe {
+                            let p = r.as_ptr();
+                            std::slice::from_raw_parts(p, r.len())
+                        };
+
+                        SpidevTransfer::read_write(w, r)
+                    }
+                }
+            })
+            .collect();
+
+        // Execute transfer
+        self.0.transfer_multiple(&mut messages)?;
+
+        Ok(())
+    }
+}
+
 impl ops::Deref for Spidev {
     type Target = spidev::Spidev;