Enable rp235x doc tests, fixup feature doc

The rp235x doc test requires an unfortunate workaround using a private
feature, "_test", in order compile.

Author: CBJamo

.github/ci/test.sh

@@ -21,7 +21,8 @@ cargo test --manifest-path ./embassy-boot/Cargo.toml --features ed25519-salty
 
 cargo test --manifest-path ./embassy-nrf/Cargo.toml --no-default-features --features nrf52840,time-driver-rtc1,gpiote
 
-cargo test --manifest-path ./embassy-rp/Cargo.toml --no-default-features --features time-driver,rp2040
+cargo test --manifest-path ./embassy-rp/Cargo.toml --no-default-features --features time-driver,rp2040,_test
+cargo test --manifest-path ./embassy-rp/Cargo.toml --no-default-features --features time-driver,rp235xa,_test
 
 cargo test --manifest-path ./embassy-stm32/Cargo.toml --no-default-features --features stm32f429vg,exti,time-driver-any,exti
 cargo test --manifest-path ./embassy-stm32/Cargo.toml --no-default-features --features stm32f732ze,exti,time-driver-any,exti

embassy-rp/Cargo.toml

@@ -98,10 +98,13 @@ rp235xa = ["_rp235x"]
 ## Configure the hal for use with the rp235xB
 rp235xb = ["_rp235x"]
 
-# Add a binary-info header block containing picotool-compatible metadata.
-#
-# Takes up a little flash space, but picotool can then report the name of your
-# program and other details.
+# hack around cortex-m peripherals being wrong when running tests.
+_test = []
+
+## Add a binary-info header block containing picotool-compatible metadata.
+##
+## Takes up a little flash space, but picotool can then report the name of your
+## program and other details.
 binary-info = [ "rt" ]
 
 [dependencies]

embassy-rp/src/lib.rs

@@ -469,7 +469,7 @@ pub fn install_core0_stack_guard() -> Result<(), ()> {
     unsafe { install_stack_guard(core::ptr::addr_of_mut!(_stack_end)) }
 }
 
-#[cfg(feature = "rp2040")]
+#[cfg(all(feature = "rp2040", not(feature = "_test")))]
 #[inline(always)]
 fn install_stack_guard(stack_bottom: *mut usize) -> Result<(), ()> {
     let core = unsafe { cortex_m::Peripherals::steal() };
@@ -497,7 +497,7 @@ fn install_stack_guard(stack_bottom: *mut usize) -> Result<(), ()> {
     Ok(())
 }
 
-#[cfg(all(feature = "_rp235x", not(test)))]
+#[cfg(all(feature = "_rp235x", not(feature = "_test")))]
 #[inline(always)]
 fn install_stack_guard(stack_bottom: *mut usize) -> Result<(), ()> {
     let core = unsafe { cortex_m::Peripherals::steal() };
@@ -517,7 +517,7 @@ fn install_stack_guard(stack_bottom: *mut usize) -> Result<(), ()> {
 
 // This is to hack around cortex_m defaulting to ARMv7 when building tests,
 // so the compile fails when we try to use ARMv8 peripherals.
-#[cfg(test)]
+#[cfg(feature = "_test")]
 #[inline(always)]
 fn install_stack_guard(_stack_bottom: *mut usize) -> Result<(), ()> {
     Ok(())