From 95aeedf97fa3d5846d14253f3cc95817384837f6 Mon Sep 17 00:00:00 2001
From: chrysn <chrysn@fsfe.org>
Date: Sun, 5 Jan 2025 22:23:05 +0100
Subject: [PATCH] tests/spi: Test SpiBus

---
 tests/spi/Cargo.toml |  1 +
 tests/spi/src/lib.rs | 51 ++++++++++++++++++++++++++++++++------------
 2 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/tests/spi/Cargo.toml b/tests/spi/Cargo.toml
index 19550df..d771c6a 100644
--- a/tests/spi/Cargo.toml
+++ b/tests/spi/Cargo.toml
@@ -13,3 +13,4 @@ panic = "abort"
 [dependencies]
 riot-wrappers = { path = "../..", features = [ "set_panic_handler", "panic_handler_format" ] }
 embedded-hal = "1"
+embedded-hal-bus = "0.2.0"
diff --git a/tests/spi/src/lib.rs b/tests/spi/src/lib.rs
index 79b6c0b..727986a 100644
--- a/tests/spi/src/lib.rs
+++ b/tests/spi/src/lib.rs
@@ -22,28 +22,51 @@ fn main() {
     };
 
     let cs = riot_wrappers::gpio::GPIO::from_port_and_pin(cs_num.0, cs_num.1).unwrap();
-    let spi =
-        riot_wrappers::spi::for_embedded_hal_1::SPIBus::from_number(spi_num)
-            // arbitrary parameters
-            .with_speed_1mhz()
-            .with_mode(embedded_hal::spi::MODE_2);
+    let spi = riot_wrappers::spi::for_embedded_hal_1::SPIBus::from_number(spi_num)
+        // arbitrary parameters
+        .with_speed_1mhz()
+        .with_mode(embedded_hal::spi::MODE_2);
+
+    println!("Testing with software CS");
+    // Writing a test for the SpiBus would be annoyingly repetitive compared to the one for
+    // SpiDevice; using the SpiBus through the embedded-hal-bus mechanism instead.
+    //
+    // Also, there's not really anything about this test where the use of the CS pin makes any
+    // difference in the outcome, it's more to cover the full API surface.
+    let Ok(mut spi_with_soft_cs) = embedded_hal_bus::spi::ExclusiveDevice::new(
+        spi,
+        cs.configure_as_output(riot_wrappers::gpio::OutputMode::Out).unwrap(),
+        riot_wrappers::ztimer::Clock::usec(),
+    );
+    test_on_device(&mut spi_with_soft_cs);
+
+    // ExclusiveDevice has no destructuring finalizer, so we just rebuild the pieces, which RIOT
+    // lets us do -- and it won't cause any sort of practical trouble because the exclusive device
+    // is not used any more, probably even dropped already.
+    let cs = riot_wrappers::gpio::GPIO::from_port_and_pin(cs_num.0, cs_num.1).unwrap();
+    let spi = riot_wrappers::spi::for_embedded_hal_1::SPIBus::from_number(spi_num)
+        // arbitrary parameters
+        .with_speed_1mhz()
+        .with_mode(embedded_hal::spi::MODE_2);
 
     println!("Testing with hardware CS");
     // It is not guaranteed that this is really hardware CS; could just as well be performed by
     // RIOT internally.
-    let mut spi_with_hard_cs = spi
-            .with_cs(cs)
-            .unwrap();
+    let mut spi_with_hard_cs = spi.with_cs(cs).unwrap();
     test_on_device(&mut spi_with_hard_cs);
 
-    println!("Tests done.");
+    println!("Both tests done.");
 }
 
-fn test_on_device<D: SpiDevice<Error = core::convert::Infallible>>(spi: &mut D) {
+// This is a bit .unwrap()py even though all our devices have infallible SPI (and CS) operations at
+// rumtime; can't use `let Ok(()) = …;` because the ExclusiveDevice has an Either<Infallible,
+// Infallible> type, and I haven't found an easy way to require that the associated error of D is
+// uninhabited.
+fn test_on_device<D: SpiDevice>(spi: &mut D) {
     println!("Plain transfer in place:");
     let mut buf = [0, 0, 0x12, 0x34];
     println!("Writing {:?}, …", buf);
-    let Ok(()) = spi.transfer_in_place(&mut buf);
+    spi.transfer_in_place(&mut buf).unwrap();
     println!("read {:?}.", buf);
 
     println!("Write from flash:");
@@ -51,7 +74,7 @@ fn test_on_device<D: SpiDevice<Error = core::convert::Infallible>>(spi: &mut D)
     // read flash.
     let buf = [0, 0, 0x12, 0x34];
     println!("Writing {:?}.", buf);
-    let Ok(()) = spi.write(&buf);
+    spi.write(&buf).unwrap();
 
     println!("Performing complex sequence:");
     let writebuf = [0; 300];
@@ -64,7 +87,7 @@ fn test_on_device<D: SpiDevice<Error = core::convert::Infallible>>(spi: &mut D)
         Operation::Read(&mut readbuf1),
         Operation::Read(&mut readbuf2),
     ];
-    let Ok(()) = spi.transaction(&mut operations);
+    spi.transaction(&mut operations).unwrap();
     println!(
         "Wrote [0; 300], read into {:?} and {:?}",
         readbuf1, readbuf2
@@ -73,7 +96,7 @@ fn test_on_device<D: SpiDevice<Error = core::convert::Infallible>>(spi: &mut D)
     println!("Plain transfer in place:");
     let writebuf = [0, 0];
     let mut readbuf = [0xff; 10];
-    let Ok(()) = spi.transfer(&mut readbuf, &writebuf);
+    spi.transfer(&mut readbuf, &writebuf).unwrap();
     println!(
         "In mixed transfer, wrote [0; 2], and continued reading into {:?}.",
         readbuf