Try to reduce the pretty drastic amount of CI checks we're currently running

Author: datdenkikniet

.github/workflows/build.yml

@@ -90,7 +90,7 @@ jobs:
         run: |
           cargo build --release --target=${{ matrix.target }} --features ${{ matrix.features }}
 
-  build-ptp:
+  build-no-ptp:
     name: build-no-ptp
     runs-on: ubuntu-20.04
     strategy:
@@ -117,7 +117,8 @@ jobs:
         run: |
           cargo build --release --target=${{ matrix.target }} --features ${{ matrix.features }} --no-default-features
 
-  # Examples
+  # Test that all of the examples compile
+  # for stm32f429
   examples:
     name: examples
     runs-on: ubuntu-20.04
@@ -138,21 +139,44 @@ jobs:
             features: ptp
           - example: timesync-client
             features: ptp
+        toolchain:
+          - stable
+        target:
+          - thumbv7em-none-eabi
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Install Rust ${{ matrix.toolchain }} with target (${{ matrix.target }})
+        run: |
+          rustup set profile minimal
+          rustup override set ${{ matrix.toolchain }}
+          rustup target add ${{ matrix.target }}
+
+      - name: Build example ${{ matrix.example.example }} for stm32f429
+        run: |
+          cargo build --release --target=${{ matrix.target }} --example ${{ matrix.example.example }} --features stm32f429,${{ matrix.example.features }}
+  
+  # Test that all the code shared with other MCU families also compiles
+  examples-common:
+    name: examples-common
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        toolchain:
+          - stable
+        target:
+          - thumbv7em-none-eabi
         mcu:
           - stm32f107
           - stm32f429
           - stm32f745
-        toolchain:
-          - stable
-        target:
-          - thumbv7m-none-eabi
         pins:
           - nucleo
           - default
         pps:
           - default
           - alternate
-
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -163,9 +187,9 @@ jobs:
           rustup override set ${{ matrix.toolchain }}
           rustup target add ${{ matrix.target }}
 
-      - name: Build example ${{ matrix.example.example }} for ${{ matrix.mcu }}, eth pins ${{ matrix.pins }}, pps pin ${{ matrix.pps }}
+      - name: Build examples common file for ${{ matrix.mcu }}, eth pins ${{ matrix.pins }}, pps pin ${{ matrix.pps }}
         run: |
-          STM32_ETH_EXAMPLE_PPS=${{ matrix.pps }} STM32_ETH_EXAMPLE_PINS=${{ matrix.pins }} cargo build --release --target=${{ matrix.target }} --example ${{ matrix.example.example}} --features ${{ matrix.mcu }},${{ matrix.example.features }}
+          STM32_ETH_EXAMPLE_PPS_PIN=${{ matrix.pps}} STM32_ETH_EXAMPLE_PINS=${{ matrix.pins }} cargo check --release --target=${{ matrix.target }} --example common --features ${{ matrix.mcu }},defmt,smoltcp-phy,ptp
 
   # Refs: https://github.com/rust-lang/crater/blob/9ab6f9697c901c4a44025cf0a39b73ad5b37d198/.github/workflows/bors.yml#L125-L149
   #
@@ -179,6 +203,8 @@ jobs:
       - build
       - test
       - examples
+      - examples-common
+      - build-no-ptp
     runs-on: ubuntu-20.04
     steps:
       - name: Mark the job as a success

Cargo.toml

@@ -74,6 +74,12 @@ panic-probe = { version = "0.3", features = [ "print-defmt" ] }
 systick-monotonic = "1.0"
 smoltcp = { version = "0.9", features = [ "medium-ethernet", "proto-ipv4", "socket-udp", "socket-tcp", "defmt" ], default-features = false }
 
+# This isn't an actual example. It just exists so we can easily
+# test the common items :)
+[[example]]
+name = "common"
+required-features = ["defmt", "smoltcp-phy", "ptp"]
+
 [[example]]
 name = "pktgen"
 required-features = [ "defmt" ]

examples/common.rs

@@ -1,9 +1,13 @@
 #![allow(unused_attributes)]
+#![no_std]
 
 //! Common features used in examples.
 //!
 //! Note that this module isn't an example by itself.
 
+use defmt_rtt as _;
+use panic_probe as _;
+
 use stm32_eth::{
     hal::{gpio::GpioExt, rcc::Clocks},
     PartsIn,
@@ -14,6 +18,12 @@ pub use pins::{setup_pins, Gpio};
 use fugit::RateExtU32;
 use stm32_eth::hal::rcc::RccExt;
 
+// This is here so that we can build the `common.rs` example individually for
+// each supported MCU family. That way we can be reasonably sure that all examples
+// compile, without having to compile all of them each time.
+#[allow(unused)]
+fn main() {}
+
 /// Setup the clocks and return clocks and a GPIO struct that
 /// can be used to set up all of the pins.
 ///