Add revert state in embassy-boot

The revert state signals that a firmware revert has taken place,
allowing the application to know if a firmware update attempt was
reverted.

embassy-boot/src/boot_loader.rs

@@ -5,7 +5,7 @@ use embassy_sync::blocking_mutex::raw::NoopRawMutex;
 use embassy_sync::blocking_mutex::Mutex;
 use embedded_storage::nor_flash::{NorFlash, NorFlashError, NorFlashErrorKind};
 
-use crate::{State, BOOT_MAGIC, DFU_DETACH_MAGIC, STATE_ERASE_VALUE, SWAP_MAGIC};
+use crate::{State, DFU_DETACH_MAGIC, REVERT_MAGIC, STATE_ERASE_VALUE, SWAP_MAGIC};
 
 /// Errors returned by bootloader
 #[derive(PartialEq, Eq, Debug)]
@@ -276,7 +276,7 @@ impl<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash> BootLoader<ACTIVE, DFU, S
                 self.state.erase(0, self.state.capacity() as u32)?;
 
                 // Set magic
-                state_word.fill(BOOT_MAGIC);
+                state_word.fill(REVERT_MAGIC);
                 self.state.write(0, state_word)?;
             }
         }
@@ -411,6 +411,8 @@ impl<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash> BootLoader<ACTIVE, DFU, S
             Ok(State::Swap)
         } else if !state_word.iter().any(|&b| b != DFU_DETACH_MAGIC) {
             Ok(State::DfuDetach)
+        } else if !state_word.iter().any(|&b| b != REVERT_MAGIC) {
+            Ok(State::Revert)
         } else {
             Ok(State::Boot)
         }

embassy-boot/src/firmware_updater/asynch.rs

@@ -289,7 +289,8 @@ impl<'d, STATE: NorFlash> FirmwareState<'d, STATE> {
 
     // Make sure we are running a booted firmware to avoid reverting to a bad state.
     async fn verify_booted(&mut self) -> Result<(), FirmwareUpdaterError> {
-        if self.get_state().await? == State::Boot {
+        let state = self.get_state().await?;
+        if state == State::Boot || state == State::DfuDetach || state == State::Revert {
             Ok(())
         } else {
             Err(FirmwareUpdaterError::BadState)

embassy-boot/src/firmware_updater/blocking.rs

@@ -324,7 +324,8 @@ impl<'d, STATE: NorFlash> BlockingFirmwareState<'d, STATE> {
 
     // Make sure we are running a booted firmware to avoid reverting to a bad state.
     fn verify_booted(&mut self) -> Result<(), FirmwareUpdaterError> {
-        if self.get_state()? == State::Boot || self.get_state()? == State::DfuDetach {
+        let state = self.get_state()?;
+        if state == State::Boot || state == State::DfuDetach || state == State::Revert {
             Ok(())
         } else {
             Err(FirmwareUpdaterError::BadState)

embassy-boot/src/lib.rs

@@ -25,6 +25,7 @@ pub use firmware_updater::{
     FirmwareUpdaterError,
 };
 
+pub(crate) const REVERT_MAGIC: u8 = 0xC0;
 pub(crate) const BOOT_MAGIC: u8 = 0xD0;
 pub(crate) const SWAP_MAGIC: u8 = 0xF0;
 pub(crate) const DFU_DETACH_MAGIC: u8 = 0xE0;
@@ -37,6 +38,8 @@ pub enum State {
     Boot,
     /// Bootloader has swapped the active partition with the dfu partition and will attempt boot.
     Swap,
+    /// Bootloader has reverted the active partition with the dfu partition and will attempt boot.
+    Revert,
     /// Application has received a request to reboot into DFU mode to apply an update.
     DfuDetach,
 }
@@ -157,6 +160,9 @@ mod tests {
         // Running again should cause a revert
         assert_eq!(State::Swap, bootloader.prepare_boot(&mut page).unwrap());
 
+        // Next time we know it was reverted
+        assert_eq!(State::Revert, bootloader.prepare_boot(&mut page).unwrap());
+
         let mut read_buf = [0; FIRMWARE_SIZE];
         flash.active().read(0, &mut read_buf).unwrap();
         assert_eq!(ORIGINAL, read_buf);