Various build size optimizations

firmware/.cargo/config.toml

@@ -1,8 +1,12 @@
 [target.thumbv7em-none-eabihf]
 runner = 'probe-rs run --chip STM32F411CEUx'
+rustflags = ["-Clinker-plugin-lto"]
 
 [build]
 target = "thumbv7em-none-eabihf"
 
 [env]
 DEFMT_LOG = "debug"
+
+[unstable]
+build-std = ["compiler_builtins", "core"]

firmware/Cargo.lock

@@ -769,7 +769,6 @@ dependencies = [
  "base64",
  "cortex-m",
  "cortex-m-rt",
- "critical-section",
  "defmt 1.0.1",
  "defmt-rtt",
  "embassy-executor",
@@ -781,6 +780,7 @@ dependencies = [
  "embedded-graphics",
  "embedded-hal-bus",
  "epd-waveshare",
+ "panic-abort",
  "panic-probe",
  "postcard",
  "serde",
@@ -844,6 +844,12 @@ version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
+[[package]]
+name = "panic-abort"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e20e6499bbbc412f280b04a42346b356c6fa0753d5fd22b7bd752ff34c778ee"
+
 [[package]]
 name = "panic-probe"
 version = "1.0.0"

firmware/Cargo.toml

@@ -10,7 +10,6 @@ cortex-m = { version = "0.7.7", features = [
   "critical-section-single-core",
 ] }
 cortex-m-rt = "0.7.5"
-critical-section = "1.2.0"
 defmt = "1.0.1"
 defmt-rtt = "1.1.0"
 embassy-executor = { version = "0.9.1", features = [
@@ -38,6 +37,7 @@ embassy-usb = { version = "0.5.1", features = ["defmt"] }
 embedded-graphics = { version = "0.8.1", features = ["defmt"] }
 embedded-hal-bus = { version = "0.3.0", features = ["async"] }
 epd-waveshare = "0.6.0"
+panic-abort = "0.3.2"
 panic-probe = { version = "1.0.0", features = ["print-defmt"] }
 postcard = { version = "1.1.3", features = ["defmt"] }
 serde = { version = "1.0.228", default-features = false, features = ["derive"] }
@@ -45,6 +45,8 @@ static_cell = "2.1.1"
 
 [profile.dev]
 opt-level = "s"
+lto = "fat"
 
 [profile.release]
-opt-level = "s"
+opt-level = "z"
+lto = "fat"

firmware/src/app.rs

@@ -140,7 +140,7 @@ impl App {
 
     async fn handle_get_identification(&mut self) {
         self.write_response(Response::GetIdentification {
-            serial: uid_base64(),
+            serial: uid_base64().await,
             model: DeviceType::BWRev1,
         })
         .await;

firmware/src/main.rs

@@ -6,6 +6,7 @@ use crate::{
     epd::Epd,
     midi::{make_midi_class, make_usb_builder, usb_task},
 };
+
 use defmt_rtt as _;
 use embassy_executor::{Spawner, main};
 use embassy_stm32::{
@@ -14,6 +15,9 @@ use embassy_stm32::{
     time::Hertz,
     usb::{self},
 };
+#[cfg(not(debug_assertions))]
+use panic_abort as _;
+#[cfg(debug_assertions)]
 use panic_probe as _;
 
 macro_rules! static_ref {
@@ -68,7 +72,7 @@ async fn main(spawner: Spawner) {
         peri.SPI1, peri.PA4, peri.PA5, peri.PA7, peri.PB10, peri.PB0, peri.PB1,
     );
 
-    let mut usb_builder = make_usb_builder(peri.USB_OTG_FS, peri.PA12, peri.PA11);
+    let mut usb_builder = make_usb_builder(peri.USB_OTG_FS, peri.PA12, peri.PA11).await;
     let midi = make_midi_class(&mut usb_builder);
 
     spawner.must_spawn(usb_task(usb_builder));

firmware/src/midi.rs

@@ -1,4 +1,3 @@
-use defmt_rtt as _;
 use embassy_executor::task;
 use embassy_stm32::{
     Peri,
@@ -6,7 +5,6 @@ use embassy_stm32::{
     usb::{self, DmPin, DpPin},
 };
 use embassy_usb::{UsbVersion, class::midi::MidiClass};
-use panic_probe as _;
 use static_cell::StaticCell;
 
 use crate::{Irqs, uid};
@@ -15,19 +13,19 @@ pub type UsbDriver = usb::Driver<'static, USB_OTG_FS>;
 pub type UsbBuilder = embassy_usb::Builder<'static, UsbDriver>;
 pub type UsbMidi = MidiClass<'static, UsbDriver>;
 
-pub fn make_usb_builder(
+pub async fn make_usb_builder(
     peri: Peri<'static, USB_OTG_FS>,
     dp: Peri<'static, impl DpPin<USB_OTG_FS>>,
     dm: Peri<'static, impl DmPin<USB_OTG_FS>>,
 ) -> UsbBuilder {
-    let ep_out_buffer = static_ref!([u8; 4096] = [0; 4096]);
+    let ep_out_buffer = static_ref!([u8; 256] = [0; 256]);
     let config_descriptor = static_ref!([u8; 256] = [0; 256]);
     let control_buf = static_ref!([u8; 256] = [0; 256]);
 
     let mut config = embassy_usb::Config::new(0x1209, 0xc9c9);
     config.manufacturer = Some("Project Daylily");
     config.product = Some("Inkclip BW");
-    config.serial_number = Some(uid::uid_base64());
+    config.serial_number = Some(uid::uid_base64().await);
     config.bcd_usb = UsbVersion::Two;
 
     let usb_driver = usb::Driver::new_fs(peri, Irqs, dp, dm, ep_out_buffer, usb::Config::default());

firmware/src/uid.rs

@@ -1,20 +1,18 @@
 use base64::prelude::*;
 use embassy_stm32::uid::uid;
+use embassy_sync::once_lock::OnceLock;
 
-pub fn uid_base64() -> &'static str {
-    unsafe { core::str::from_utf8_unchecked(uid_base64_bytes()) }
+pub async fn uid_base64() -> &'static str {
+    unsafe { core::str::from_utf8_unchecked(uid_base64_bytes().await) }
 }
 
-#[allow(static_mut_refs)]
-pub fn uid_base64_bytes() -> &'static [u8; 16] {
-    static mut UID_BASE64: [u8; 16] = [0; 16];
-    static mut LOADED: bool = false;
-    critical_section::with(|_| unsafe {
-        if !LOADED {
-            let uid = uid();
-            BASE64_STANDARD.encode_slice(uid, &mut UID_BASE64).unwrap();
-            LOADED = true;
-        }
-    });
-    unsafe { &*core::ptr::addr_of!(UID_BASE64) }
+pub async fn uid_base64_bytes() -> &'static [u8; 16] {
+    static UID_BASE64: OnceLock<[u8; 16]> = OnceLock::new();
+    UID_BASE64.get_or_init(|| {
+        let mut b64 = [0u8; 16];
+        BASE64_STANDARD
+            .encode_slice(uid(), &mut b64)
+            .expect("12-byte UID encoded to 16 bytes of base64");
+        b64
+    })
 }