cortex-m-pac crate: standard traits and result handling for Cortex-M targets

.github/workflows/ci.yml

@@ -30,4 +30,8 @@ jobs:
         with:
           toolchain: ${{ matrix.rust }}
       - name: Run tests
+        if: ${{ matrix.rust != '1.61.0' }}
         run: cargo test --all --exclude cortex-m-rt --exclude testsuite --features cortex-m/critical-section-single-core
+      - name: Run tests for 1.61.0 (need to exclude cortex-m-pac)
+        if: ${{ matrix.rust == '1.61.0' }}
+        run: cargo test --all --exclude cortex-m-rt --exclude testsuite --exclude cortex-m-pac --features cortex-m/critical-section-single-core

Cargo.toml

@@ -2,6 +2,7 @@
 resolver = "2"
 members = [
     "cortex-m",
+    "cortex-m-pac",
     "cortex-m-rt",
     "cortex-m-semihosting",
     "panic-itm",

cortex-m-pac/CHANGELOG.md

@@ -0,0 +1,8 @@
+# Change Log
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]

cortex-m-pac/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "cortex-m-pac"
+version = "0.1.0"
+edition = "2021"
+rust-version = "1.81"
+repository = "https://github.com/rust-embedded/cortex-m"
+authors = ["The Cortex-M Team <[email protected]>",]
+categories = ["embedded", "hardware-support", "no-std"]
+description = "Low level access to Cortex-M processors"
+documentation = "https://docs.rs/cortex-m-pac"
+keywords = ["arm", "cortex-m", "register", "peripheral"]
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+[package.metadata.docs.rs]
+targets = [
+    "thumbv8m.main-none-eabihf",
+    "thumbv6m-none-eabi",
+    "thumbv7em-none-eabi",
+    "thumbv7em-none-eabihf",
+    "thumbv7m-none-eabi",
+    "thumbv8m.base-none-eabi",
+    "thumbv8m.main-none-eabi"
+]

cortex-m-pac/README.md

@@ -0,0 +1,40 @@
+[![crates.io](https://img.shields.io/crates/d/cortex-m-pac.svg)](https://crates.io/crates/cortex-m-pac)
+[![crates.io](https://img.shields.io/crates/v/cortex-m-pac.svg)](https://crates.io/crates/cortex-m-pac)
+
+# `cortex-m-pac`
+
+> Target-specific traits to be implemented by PACs
+
+This project is developed and maintained by the [Cortex-M team][team].
+
+## [Documentation](https://docs.rs/crate/cortex-m-pac)
+
+## Minimum Supported Rust Version (MSRV)
+
+This crate is guaranteed to compile on stable Rust 1.60 and up. It *might*
+compile with older versions but that may change in any new patch release.
+
+## License
+
+Copyright 2024 [Cortex-M team][team]
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.
+
+## Code of Conduct
+
+Contribution to this crate is organized under the terms of the [Rust Code of
+Conduct][CoC], the maintainer of this crate, the [Cortex-M team][team], promises
+to intervene to uphold that code of conduct.
+
+[CoC]: CODE_OF_CONDUCT.md
+[team]: https://github.com/rust-embedded/wg#the-cortex-m-team

cortex-m-pac/src/lib.rs

@@ -0,0 +1,264 @@
+#![no_std]
+
+pub mod result;
+
+use result::Result;
+
+/// Trait for enums of target-specific exception numbers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// exceptions for a specific device. Alternatively, the `cortex-m` crate provides a default
+/// implementation. Each variant must convert to a `usize` of its exception number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on the `cortex-m` crate or on a PAC of a Cortex-M target.
+/// * This trait must only be implemented on enums of exceptions.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the exception numbers must be less than or equal to `MAX_EXCEPTION_NUMBER`.
+/// * `MAX_EXCEPTION_NUMBER` must coincide with the highest allowed exception number.
+pub unsafe trait ExceptionNumber: Copy {
+    /// Highest number assigned to an exception.
+    const MAX_EXCEPTION_NUMBER: usize;
+
+    /// Converts an exception to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid exception.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Trait for enums of target-specific interrupt numbers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// interrupts for a specific device. Each variant must convert to a `usize` of its interrupt number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on a PAC of a Cortex-M target.
+/// * This trait must only be implemented on enums of interrupts.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the interrupt numbers must be less than or equal to `MAX_INTERRUPT_NUMBER`.
+/// * `MAX_INTERRUPT_NUMBER` must coincide with the highest allowed interrupt number.
+pub unsafe trait InterruptNumber: Copy {
+    /// Highest number assigned to an interrupt source.
+    const MAX_INTERRUPT_NUMBER: usize;
+
+    /// Converts an interrupt source to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid interrupt.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Trait for enums of priority levels.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// priority numbers for a specific device. Each variant must convert to a `usize` of its priority level.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on a PAC of a Cortex-M target.
+/// * This trait must only be implemented on enums of priority levels.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted).
+/// * Each enum variant must always return the same value (do not change at runtime).
+/// * All the priority level numbers must be less than or equal to `MAX_PRIORITY_NUMBER`.
+/// * `MAX_PRIORITY_NUMBER` must coincide with the highest allowed priority number.
+pub unsafe trait PriorityNumber: Copy {
+    /// Number assigned to the highest priority level.
+    const MAX_PRIORITY_NUMBER: usize;
+
+    /// Converts a priority level to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid priority level.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+/// Trait for enums of core identifiers.
+///
+/// This trait should be implemented by a peripheral access crate (PAC) on its enum of available
+/// cores for a specific device. Each variant must convert to a `usize` of its core ID number.
+///
+/// # Safety
+///
+/// * This trait must only be implemented on a PAC of a Cortex-M target.
+/// * This trait must only be implemented on enums of core IDs.
+/// * Each enum variant must represent a distinct value (no duplicates are permitted),
+/// * Each anum variant must always return the same value (do not change at runtime).
+/// * All the core ID numbers must be less than or equal to `MAX_CORE_ID_NUMBER`.
+/// * `MAX_CORE_ID_NUMBER` must coincide with the highest allowed core ID number.
+pub unsafe trait CoreIdNumber: Copy {
+    /// Highest number assigned to a core.
+    const MAX_CORE_ID_NUMBER: usize;
+
+    /// Converts a Core ID to its corresponding number.
+    fn number(self) -> usize;
+
+    /// Tries to convert a number to a valid Core ID.
+    fn from_number(value: usize) -> Result<Self>;
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::result::Error;
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Exception {
+        E1 = 1,
+        E3 = 3,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Interrupt {
+        I1 = 1,
+        I2 = 2,
+        I4 = 4,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum Priority {
+        P0 = 0,
+        P1 = 1,
+        P2 = 2,
+        P3 = 3,
+    }
+
+    #[derive(Clone, Copy, Debug, Eq, PartialEq)]
+    enum CoreId {
+        H0 = 0,
+        H1 = 1,
+        H2 = 2,
+    }
+
+    unsafe impl ExceptionNumber for Exception {
+        const MAX_EXCEPTION_NUMBER: usize = Self::E3 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                1 => Ok(Exception::E1),
+                3 => Ok(Exception::E3),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl InterruptNumber for Interrupt {
+        const MAX_INTERRUPT_NUMBER: usize = Self::I4 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                1 => Ok(Interrupt::I1),
+                2 => Ok(Interrupt::I2),
+                4 => Ok(Interrupt::I4),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl PriorityNumber for Priority {
+        const MAX_PRIORITY_NUMBER: usize = Self::P3 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                0 => Ok(Priority::P0),
+                1 => Ok(Priority::P1),
+                2 => Ok(Priority::P2),
+                3 => Ok(Priority::P3),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    unsafe impl CoreIdNumber for CoreId {
+        const MAX_CORE_ID_NUMBER: usize = Self::H2 as usize;
+
+        #[inline]
+        fn number(self) -> usize {
+            self as _
+        }
+
+        #[inline]
+        fn from_number(number: usize) -> Result<Self> {
+            match number {
+                0 => Ok(CoreId::H0),
+                1 => Ok(CoreId::H1),
+                2 => Ok(CoreId::H2),
+                _ => Err(Error::InvalidVariant(number)),
+            }
+        }
+    }
+
+    #[test]
+    fn check_exception_enum() {
+        assert_eq!(Exception::E1.number(), 1);
+        assert_eq!(Exception::E3.number(), 3);
+
+        assert_eq!(Exception::from_number(0), Err(Error::InvalidVariant(0)));
+        assert_eq!(Exception::from_number(1), Ok(Exception::E1));
+        assert_eq!(Exception::from_number(2), Err(Error::InvalidVariant(2)));
+        assert_eq!(Exception::from_number(3), Ok(Exception::E3));
+        assert_eq!(Exception::from_number(4), Err(Error::InvalidVariant(4)));
+    }
+
+    #[test]
+    fn check_interrupt_enum() {
+        assert_eq!(Interrupt::I1.number(), 1);
+        assert_eq!(Interrupt::I2.number(), 2);
+        assert_eq!(Interrupt::I4.number(), 4);
+
+        assert_eq!(Interrupt::from_number(0), Err(Error::InvalidVariant(0)));
+        assert_eq!(Interrupt::from_number(1), Ok(Interrupt::I1));
+        assert_eq!(Interrupt::from_number(2), Ok(Interrupt::I2));
+        assert_eq!(Interrupt::from_number(3), Err(Error::InvalidVariant(3)));
+        assert_eq!(Interrupt::from_number(4), Ok(Interrupt::I4));
+        assert_eq!(Interrupt::from_number(5), Err(Error::InvalidVariant(5)));
+    }
+
+    #[test]
+    fn check_priority_enum() {
+        assert_eq!(Priority::P0.number(), 0);
+        assert_eq!(Priority::P1.number(), 1);
+        assert_eq!(Priority::P2.number(), 2);
+        assert_eq!(Priority::P3.number(), 3);
+
+        assert_eq!(Priority::from_number(0), Ok(Priority::P0));
+        assert_eq!(Priority::from_number(1), Ok(Priority::P1));
+        assert_eq!(Priority::from_number(2), Ok(Priority::P2));
+        assert_eq!(Priority::from_number(3), Ok(Priority::P3));
+        assert_eq!(Priority::from_number(4), Err(Error::InvalidVariant(4)));
+    }
+
+    #[test]
+    fn check_core_id_enum() {
+        assert_eq!(CoreId::H0.number(), 0);
+        assert_eq!(CoreId::H1.number(), 1);
+        assert_eq!(CoreId::H2.number(), 2);
+
+        assert_eq!(CoreId::from_number(0), Ok(CoreId::H0));
+        assert_eq!(CoreId::from_number(1), Ok(CoreId::H1));
+        assert_eq!(CoreId::from_number(2), Ok(CoreId::H2));
+        assert_eq!(CoreId::from_number(3), Err(Error::InvalidVariant(3)));
+    }
+}

cortex-m-pac/src/result.rs

@@ -0,0 +1,61 @@
+use core::fmt;
+
+/// Convenience alias for the [Result](core::result::Result) type for the library.
+pub type Result<T> = core::result::Result<T, Error>;
+
+/// Represents error variants for the library.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[non_exhaustive]
+pub enum Error {
+    /// Attempted out-of-bounds access.
+    IndexOutOfBounds {
+        index: usize,
+        min: usize,
+        max: usize,
+    },
+    /// Invalid field value.
+    InvalidFieldValue {
+        field: &'static str,
+        value: usize,
+        bitmask: usize,
+    },
+    /// Invalid value of a register field that does not match any known variants.
+    InvalidFieldVariant { field: &'static str, value: usize },
+    /// Invalid value.
+    InvalidValue { value: usize, bitmask: usize },
+    /// Invalid value that does not match any known variants.
+    InvalidVariant(usize),
+    /// Unimplemented function or type.
+    Unimplemented,
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::IndexOutOfBounds { index, min, max } => write!(
+                f,
+                "out-of-bounds access, index: {index}, min: {min}, max: {max}"
+            ),
+            Self::InvalidFieldValue {
+                field,
+                value,
+                bitmask,
+            } => write!(
+                f,
+                "invalid {field} field value: {value:#x}, valid bitmask: {bitmask:#x}",
+            ),
+            Self::InvalidFieldVariant { field, value } => {
+                write!(f, "invalid {field} field variant: {value:#x}")
+            }
+            Self::InvalidValue { value, bitmask } => {
+                write!(f, "invalid value: {value:#x}, valid bitmask: {bitmask:#x}",)
+            }
+            Self::InvalidVariant(value) => {
+                write!(f, "invalid variant: {value:#x}")
+            }
+            Self::Unimplemented => write!(f, "unimplemented"),
+        }
+    }
+}
+
+impl core::error::Error for Error {}