Make default boot state user configurable

examples/rt685s/bootloader/src/main.rs

@@ -45,6 +45,8 @@ impl ec_slimloader_imxrt::ImxrtConfig for Config {
     }
 }
 
+impl ec_slimloader::BootStatePolicy for Config {}
+
 #[embassy_executor::main]
 async fn main(_spawner: Spawner) -> ! {
     ec_slimloader::start::<ec_slimloader_imxrt::Imxrt<Config>, JOURNAL_BUFFER_SIZE>(Config).await

libs/ec-slimloader-imxrt/src/lib.rs

@@ -17,7 +17,7 @@ mod mbi;
 use core::ops::Range;
 
 use defmt_or_log::{error, info, panic};
-use ec_slimloader::{Board, BootError};
+use ec_slimloader::{Board, BootError, BootStatePolicy};
 use ec_slimloader_state::flash::FlashJournal;
 use ec_slimloader_state::state::Slot;
 use embassy_embedded_hal::adapter::BlockingAsync;
@@ -77,7 +77,7 @@ impl<C: ImxrtConfig> CheckImage for Imxrt<C> {
     }
 }
 
-impl<C: ImxrtConfig> Board for Imxrt<C> {
+impl<C: ImxrtConfig + BootStatePolicy> Board for Imxrt<C> {
     type Config = C;
 
     async fn init<const JOURNAL_BUFFER_SIZE: usize>(config: Self::Config) -> Self {

libs/ec-slimloader/src/lib.rs

@@ -5,14 +5,27 @@ use ec_slimloader_state::flash::FlashJournal;
 use ec_slimloader_state::state::{Slot, State, Status};
 use embedded_storage_async::nor_flash::NorFlash;
 
+/// A trait for application specific configurations.
+pub trait BootStatePolicy {
+    /// Get the application specific default boot state.
+    fn default_state() -> State {
+        State::new(Status::Initial, unwrap!(Slot::try_from(0)), unwrap!(Slot::try_from(0)))
+    }
+
+    /// Allows application specific validation of the boot state.
+    fn is_valid_state(_state: &State) -> bool {
+        true
+    }
+}
+
 /// A board that can boot an application image.
 ///
 /// Typically a board needs to support the intrinsics for some microcontroller and
 /// contain non volatile memory that stores the multiple images and bootloading state.
 #[allow(async_fn_in_trait)]
 pub trait Board {
     /// Type used to instantiate a [Board] implementation.
-    type Config;
+    type Config: BootStatePolicy;
 
     /// Initialize the [Board], can only be called once.
     async fn init<const JOURNAL_BUFFER_SIZE: usize>(config: Self::Config) -> Self;
@@ -82,15 +95,24 @@ pub async fn start<B: Board, const JOURNAL_BUFFER_SIZE: usize>(config: B::Config
     let mut state: State = match state {
         Some(state) => {
             info!("Latest state fetched from journal: {:?}", state);
-            *state
+            if B::Config::is_valid_state(state) {
+                *state
+            } else {
+                let default_state = B::Config::default_state();
+                warn!(
+                    "State {:?} is invalid per application policy, using default state {:?}",
+                    state, default_state
+                );
+                default_state
+            }
         }
         None => {
-            let slot = unwrap!(Slot::try_from(0));
+            let default_state = B::Config::default_state();
             warn!(
                 "Initial bootup and no state was loaded into the journal, attempting {:?}",
-                slot
+                default_state
             );
-            State::new(Status::Initial, slot, slot)
+            default_state
         }
     };