Make portable-atomic optional

Author: 9names

embedded-hal-bus/Cargo.toml

@@ -23,7 +23,7 @@ std = ["alloc"]
 # that does not natively support atomic CAS. If you enable this, you must also add `portable-atomic` to your crate with
 # a feature flag such as `unsafe-assume-single-core` or `critical-section` to choose how atomic CAS is implemented.
 # See https://docs.rs/portable-atomic/1.7.0/portable_atomic/#optional-features for more info.
-portable-atomic = []
+portable-atomic = ["dep:portable-atomic"]
 # Enable `embedded-hal-async` support.
 async = ["dep:embedded-hal-async"]
 # Derive `defmt::Format` from `defmt` 0.3 for enums and structs. See https://github.com/knurling-rs/defmt for more info
@@ -36,7 +36,7 @@ embedded-hal = { version = "1.0.0", path = "../embedded-hal" }
 embedded-hal-async = { version = "1.0.0", path = "../embedded-hal-async", optional = true }
 critical-section = { version = "1.0" }
 defmt-03 = { package = "defmt", version = "0.3", optional = true }
-portable-atomic = {version = "1.3", default-features = false, features = ["require-cas"]}
+portable-atomic = {version = "1.3", default-features = false, optional = true, features = ["require-cas"]}
 
 [package.metadata.docs.rs]
 features = ["std", "async"]