update for transactional landed in e-h master

Author: ryankurte

Cargo.toml

@@ -12,12 +12,11 @@ edition = "2018"
 [features]
 gpio_sysfs = ["sysfs_gpio"]
 gpio_cdev = ["gpio-cdev"]
-transactional-spi = []      # Guard for transactional SPI feature (https://github.com/rust-embedded/embedded-hal/pull/191)
 
 default = [ "gpio_cdev", "gpio_sysfs" ]
 
 [dependencies]
-embedded-hal = "=1.0.0-alpha.1"
+embedded-hal = "=1.0.0-alpha.2"
 gpio-cdev = { version = "0.3", optional = true }
 sysfs_gpio = { version = "0.5", optional = true }
 
@@ -36,4 +35,5 @@ default-features = false
 version = "0.2.2"
 
 [patch.crates-io]
-#embedded-hal = { git = "https://github.com/ryankurte/embedded-hal", branch = "feature/spi-transactions" }
+embedded-hal = { git = "https://github.com/rust-embedded/embedded-hal" }
+

src/lib.rs

@@ -259,10 +259,9 @@ impl hal::blocking::spi::Write<u8> for Spidev {
     }
 }
 
-#[cfg(feature = "transactional-spi")]
 pub use hal::blocking::spi::{Operation as SpiOperation};
 
-#[cfg(feature = "transactional-spi")]
+/// Transactional implementation batches SPI operations into a single transaction
 impl hal::blocking::spi::Transactional<u8> for Spidev {
     type Error = io::Error;
 
@@ -273,9 +272,8 @@ impl hal::blocking::spi::Transactional<u8> for Spidev {
             match a {
                 SpiOperation::Write(w) => SpidevTransfer::write(w),
                 SpiOperation::Transfer(r) => {
-                    // TODO: is spidev okay with the same array pointer
-                    // being used twice? If not, need some kind of vector 
-                    // pool that will outlive the transfer
+                    // 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())