From 71c2ba0854d57eef946bf786781563003afba5cf Mon Sep 17 00:00:00 2001
From: Robin Mueller <robin.mueller.m@pm.me>
Date: Wed, 29 Oct 2025 16:01:41 +0100
Subject: [PATCH] fix portable atomic support

---
 Cargo.toml       |  3 ++-
 README.md        |  3 +++
 justfile         |  1 +
 src/lib.rs       |  3 +++
 src/seq_count.rs | 20 ++++++++++++--------
 5 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index b91cca0..9145993 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ num_enum = { version = ">0.5, <=0.7", default-features = false }
 num-traits = { version = "0.2", default-features = false }
 serde = { version = "1", optional = true, default-features = false, features = ["derive"] }
 arbitrary-int = { version = "2" }
-portable-atomic = "1"
+portable-atomic = { version = "1", optional = true }
 bitbybit = "1.4"
 
 time = { version = "0.3", default-features = false, optional = true }
@@ -32,6 +32,7 @@ defmt = { version = "1", default-features = false, optional = true }
 [features]
 default = ["std"]
 std = ["alloc", "chrono/std", "chrono/clock", "thiserror/std"]
+portable-atomic = ["dep:portable-atomic", "portable-atomic/require-cas"]
 defmt = ["dep:defmt", "arbitrary-int/defmt"]
 serde = ["dep:serde", "chrono?/serde", "arbitrary-int/serde"]
 alloc = ["chrono?/alloc", "defmt?/alloc", "serde?/alloc"]
diff --git a/README.md b/README.md
index 7f2e05a..c2fdb6a 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,9 @@ Currently, this includes the following components:
  - [`timelib`](https://crates.io/crates/time): Add basic support for the `time` time library.
  - [`defmt`](https://defmt.ferrous-systems.com/): Add support for the `defmt` by adding the
    [`defmt::Format`](https://defmt.ferrous-systems.com/format) derive on many types.
+ - [`portable-atomic`](https://github.com/taiki-e/portable-atomic): Basic support for `portable-atomic`
+   crate in addition to the support for core atomic types. This support requires atomic CAS support
+   enabled in the portable atomic crate.
 
 # Examples
 
diff --git a/justfile b/justfile
index 75d5aee..b442f56 100644
--- a/justfile
+++ b/justfile
@@ -11,6 +11,7 @@ check:
 
 embedded:
   cargo build --target thumbv7em-none-eabihf --no-default-features
+  cargo build --target thumbv6m-none-eabi --no-default-features
 
 test:
   cargo nextest r --all-features
diff --git a/src/lib.rs b/src/lib.rs
index 5012d86..77f93fb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -37,6 +37,9 @@
 //!  - [`timelib`](https://crates.io/crates/time): Add basic support for the `time` time library.
 //!  - [`defmt`](https://defmt.ferrous-systems.com/): Add support for the `defmt` by adding the
 //!    [`defmt::Format`](https://defmt.ferrous-systems.com/format) derive on many types.
+//!  - [`portable-atomic`]: Basic support for `portable-atomic` crate in addition to the support
+//!    for core atomic types. This support requires atomic CAS support enabled in the portable
+//!    atomic crate.
 //!
 //! ## Module
 //!
diff --git a/src/seq_count.rs b/src/seq_count.rs
index c52eb2b..20d6c38 100644
--- a/src/seq_count.rs
+++ b/src/seq_count.rs
@@ -184,59 +184,63 @@ impl SequenceCounter for core::sync::atomic::AtomicU64 {
     }
 }
 
+#[cfg(feature = "portable-atomic")]
 impl SequenceCounter for portable_atomic::AtomicU8 {
     type Raw = u8;
 
     const MAX_BIT_WIDTH: usize = 8;
 
     fn get(&self) -> Self::Raw {
-        self.load(core::sync::atomic::Ordering::Relaxed)
+        self.load(portable_atomic::Ordering::Relaxed)
     }
 
     fn increment(&self) {
-        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
     }
 }
 
+#[cfg(feature = "portable-atomic")]
 impl SequenceCounter for portable_atomic::AtomicU16 {
     type Raw = u16;
 
     const MAX_BIT_WIDTH: usize = 16;
 
     fn get(&self) -> Self::Raw {
-        self.load(core::sync::atomic::Ordering::Relaxed)
+        self.load(portable_atomic::Ordering::Relaxed)
     }
 
     fn increment(&self) {
-        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
     }
 }
 
+#[cfg(feature = "portable-atomic")]
 impl SequenceCounter for portable_atomic::AtomicU32 {
     type Raw = u32;
 
     const MAX_BIT_WIDTH: usize = 32;
 
     fn get(&self) -> Self::Raw {
-        self.load(core::sync::atomic::Ordering::Relaxed)
+        self.load(portable_atomic::Ordering::Relaxed)
     }
 
     fn increment(&self) {
-        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
     }
 }
 
+#[cfg(feature = "portable-atomic")]
 impl SequenceCounter for portable_atomic::AtomicU64 {
     type Raw = u64;
 
     const MAX_BIT_WIDTH: usize = 64;
 
     fn get(&self) -> Self::Raw {
-        self.load(core::sync::atomic::Ordering::Relaxed)
+        self.load(portable_atomic::Ordering::Relaxed)
     }
 
     fn increment(&self) {
-        self.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+        self.fetch_add(1, portable_atomic::Ordering::Relaxed);
     }
 }