move flc logic into hal

Author: suaviloquence

hal/Cargo.toml

@@ -29,4 +29,7 @@ critical-section = "1.2.0"
 [features]
 rt = ["max78000/rt", "cortex-m-rt"]
 low_frequency = []
-flc-ram = []
+flc-ram = ["rt"]
+
+[build-dependencies]
+cc = "1.2.16"

hal/build.rs

@@ -0,0 +1,16 @@
+use std::{env, fs::File, io::Write, path::PathBuf};
+
+fn main() {
+    let out = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+
+    let flc_asm_path = out.join("flc_asm.s");
+    File::create(&flc_asm_path)
+        .unwrap()
+        .write_all(include_bytes!("flc_asm.s"))
+        .unwrap();
+
+    cc::Build::new().file(&flc_asm_path).compile("flc_asm");
+
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=flc_asm.s");
+}

tests/flc_asm.s hal/flc_asm.stests/flc_asm.s renamed to hal/flc_asm.s

@@ -1,4 +1,36 @@
 //! A HAL for the Analog Devices MAX78000.
+//!
+//! # Runtime
+//!
+//! If the `rt` feature is enabled, this crate uses the runtime of the [`cortex_m_rt`]
+//! crate.  Note that the HAL uses the [`pre_init`] hook internally, and it is not possible
+//! for users of the hal to specify their own `pre_init` routine.
+//!
+//! # Flash Controller
+//!
+//! If the `flc-ram` feature is enabled, this crate will expose the [`FlashController`]
+//! peripheral.  Certain routines for flash operations need to be located in RAM (instead
+//! of flash memory), so users of this feature will need to add the following section to
+//! their linker script `link.x`:
+//!
+//! ```ld
+//! .analogsucks : ALIGN(4)
+//! {
+//!   . = ALIGN(4);
+//!   __sanalogsucks = .;
+//!   *(.analogsucks .analogsucks.*);
+//! } > ANALOGSUCKS
+//!   . = ALIGN(4);
+//!   __eanalogsucks = .;
+//! } > ANALOGSUCKS AT>FLASH
+//!
+//! __sianalogsucks = LOADADDR(.analogsucks);
+//! ```
+//!
+//! where the `ANALOGSUCKS` is a memory section in RAM defined in `memory.x`.
+//!
+//! [`pre_init`]: cortex_m_rt::pre_init
+//! [`FlashController`]: peripherals::FlashController
 
 #![warn(missing_docs)]
 #![no_std]
@@ -9,7 +41,26 @@ pub use max78000;
 pub use self::max78000::Interrupt as interrupt;
 
 #[cfg(feature = "rt")]
-pub use cortex_m_rt::interrupt;
+pub use cortex_m_rt::{interrupt, pre_init};
 
 pub mod communication;
 pub mod peripherals;
+
+#[cfg(feature = "rt")]
+#[pre_init]
+unsafe fn pre_init() {
+    // load the .analogsucks section into memory
+    #[cfg(feature = "flc-ram")]
+    core::arch::asm! {
+        "ldr r0, =__sanalogsucks
+         ldr r1, =__eanalogsucks
+         ldr r2, =__sianalogsucks
+         0:
+         cmp r1, r0
+         beq 1f
+         ldm r2!, {{r3}}
+         stm r0!, {{r3}}
+         b 0b
+         1:"
+    }
+}

hal/src/lib.rs

@@ -55,8 +55,20 @@ pub enum FlashErr {
 
 /// Flash Controller peripheral.
 pub struct FlashController<'gcr, 'icc> {
+    #[expect(
+        unused,
+        reason = "the unsafe functions we call require us to hold references to these registers"
+    )]
     flc: FLC,
+    #[expect(
+        unused,
+        reason = "the unsafe functions we call require us to hold references to these registers"
+    )]
     icc: &'icc ICC0,
+    #[expect(
+        unused,
+        reason = "the unsafe functions we call require us to hold references to these registers"
+    )]
     gcr: &'gcr GCR,
 }