From dcf5d949dc58204ecc989f8a42e636985437f373 Mon Sep 17 00:00:00 2001
From: Alistair Francis <alistair.francis@wdc.com>
Date: Thu, 2 May 2024 13:53:31 +1000
Subject: [PATCH] Initial support for the Rust Embedded embedded-hal

This is very initial support for the embedded_hal [1]. This allows
general embedded Rust crates to be built on top of libtock-rs with
minimal porting effort.

This currently just stubs out the support and implements the
`digital::OutputPin` trait for GPIO pins.

1: https://docs.rs/embedded-hal/1.0.0/embedded_hal/index.html

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 Cargo.toml                 |  9 +++++++++
 README.md                  | 13 +++++++++++++
 apis/gpio/Cargo.toml       |  4 ++++
 apis/gpio/src/lib.rs       | 16 ++++++++++++++++
 platform/Cargo.toml        |  6 ++++++
 platform/src/error_code.rs |  8 ++++++++
 6 files changed, 56 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index 584a5581..76e7a1c9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,6 +15,13 @@ version = "0.1.0"
 # more information.
 rust-version = "1.74"
 
+[features]
+rust_embedded = [
+    "embedded-hal",
+    "libtock_platform/rust_embedded",
+    "libtock_gpio/rust_embedded"
+]
+
 [dependencies]
 libtock_adc = { path = "apis/adc" }
 libtock_air_quality = { path = "apis/air_quality" }
@@ -38,6 +45,8 @@ libtock_runtime = { path = "runtime" }
 libtock_sound_pressure = { path = "apis/sound_pressure" }
 libtock_temperature = { path = "apis/temperature" }
 
+embedded-hal = { version = "1.0", optional = true }
+
 [build-dependencies]
 libtock_build_scripts = { path = "build_scripts" }
 
diff --git a/README.md b/README.md
index 84b37485..7b68be0a 100644
--- a/README.md
+++ b/README.md
@@ -63,6 +63,19 @@ This script does the following steps for you:
 - create a TAB (tock application bundle)
 - if you have a J-Link compatible board connected: flash this TAB to your board (using tockloader)
 
+### Enabling rust-embedded support
+
+libtock-rs can be built to be compatible with the rust-embedded
+[embedded_hal](https://docs.rs/embedded-hal/1.0.0/embedded_hal/index.html) by
+including the following when running `make`
+
+```shell
+FEATURES=rust_embedded
+```
+
+If using libtock-rs or a sub-crate as a cargo dependency the `rust_embedded`
+can also be enabled via Cargo.
+
 ### Building a generic TAB (Tock Application Bundle) file
 
 To build your example for a variety of boards you can use
diff --git a/apis/gpio/Cargo.toml b/apis/gpio/Cargo.toml
index 16ddeb2c..d32da173 100644
--- a/apis/gpio/Cargo.toml
+++ b/apis/gpio/Cargo.toml
@@ -8,8 +8,12 @@ repository = "https://www.github.com/tock/libtock-rs"
 rust-version.workspace = true
 description = "libtock gpio driver"
 
+[features]
+rust_embedded = ["embedded-hal"]
+
 [dependencies]
 libtock_platform = { path = "../../platform" }
+embedded-hal = { version = "1.0", optional = true }
 
 [dev-dependencies]
 libtock_unittest = { path = "../../unittest" }
diff --git a/apis/gpio/src/lib.rs b/apis/gpio/src/lib.rs
index afdc41e8..ae8c3c43 100644
--- a/apis/gpio/src/lib.rs
+++ b/apis/gpio/src/lib.rs
@@ -231,6 +231,22 @@ impl<S: Syscalls> Gpio<S> {
     }
 }
 
+#[cfg(feature = "rust_embedded")]
+impl<'a, S: Syscalls> embedded_hal::digital::ErrorType for OutputPin<'a, S> {
+    type Error = ErrorCode;
+}
+
+#[cfg(feature = "rust_embedded")]
+impl<'a, S: Syscalls> embedded_hal::digital::OutputPin for OutputPin<'a, S> {
+    fn set_low(&mut self) -> Result<(), Self::Error> {
+        self.clear()
+    }
+
+    fn set_high(&mut self) -> Result<(), Self::Error> {
+        self.set()
+    }
+}
+
 #[cfg(test)]
 mod tests;
 
diff --git a/platform/Cargo.toml b/platform/Cargo.toml
index c6cf5b89..5da05582 100644
--- a/platform/Cargo.toml
+++ b/platform/Cargo.toml
@@ -12,3 +12,9 @@ name = "libtock_platform"
 repository = "https://www.github.com/tock/libtock/rs"
 rust-version.workspace = true
 version = "0.1.0"
+
+[features]
+rust_embedded = ["embedded-hal"]
+
+[dependencies]
+embedded-hal = { version = "1.0", optional = true }
diff --git a/platform/src/error_code.rs b/platform/src/error_code.rs
index 5f85446c..42eca7c8 100644
--- a/platform/src/error_code.rs
+++ b/platform/src/error_code.rs
@@ -283,3 +283,11 @@ impl TryFrom<u32> for ErrorCode {
         }
     }
 }
+
+#[cfg(feature = "rust_embedded")]
+impl embedded_hal::digital::Error for ErrorCode {
+    fn kind(&self) -> embedded_hal::digital::ErrorKind {
+        use embedded_hal::digital::ErrorKind;
+        ErrorKind::Other
+    }
+}