boot: release flash after prepare and refactor api

This refactoring of the chip specific bootloader creates the internal boot instance and aligned
buffer in the prepare stage, so that they are automatically dropped after. This unlocks a use
case where peripherals owning the flash need to be Drop'ed before load() happens.

1 files changed, 10 insertions, 23 deletions

diff --git a/embassy-boot/stm32/src/lib.rs b/embassy-boot/stm32/src/lib.rs
index 25f029423..c6350c495 100644
--- a/embassy-boot/stm32/src/lib.rs
+++ b/embassy-boot/stm32/src/lib.rs
@@ -11,28 +11,17 @@ pub use embassy_boot::{FirmwareState, FirmwareUpdater};
 use embedded_storage::nor_flash::NorFlash;
 
 /// A bootloader for STM32 devices.
-pub struct BootLoader<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash, const BUFFER_SIZE: usize> {
-    boot: embassy_boot::BootLoader<ACTIVE, DFU, STATE>,
-    aligned_buf: AlignedBuffer<BUFFER_SIZE>,
-}
-
-impl<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash, const BUFFER_SIZE: usize>
-    BootLoader<ACTIVE, DFU, STATE, BUFFER_SIZE>
-{
-    /// Create a new bootloader instance using the supplied partitions for active, dfu and state.
-    pub fn new(config: BootLoaderConfig<ACTIVE, DFU, STATE>) -> Self {
-        Self {
-            boot: embassy_boot::BootLoader::new(config),
-            aligned_buf: AlignedBuffer([0; BUFFER_SIZE]),
-        }
-    }
+pub struct BootLoader;
 
-    /// Inspect the bootloader state and perform actions required before booting, such as swapping
-    /// firmware.
-    pub fn prepare(&mut self) {
-        self.boot
-            .prepare_boot(self.aligned_buf.as_mut())
-            .expect("Boot prepare error");
+impl BootLoader {
+    /// Inspect the bootloader state and perform actions required before booting, such as swapping firmware
+    pub fn prepare<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash, const BUFFER_SIZE: usize>(
+        config: BootLoaderConfig<ACTIVE, DFU, STATE>,
+    ) -> Self {
+        let mut aligned_buf = AlignedBuffer([0; BUFFER_SIZE]);
+        let mut boot = embassy_boot::BootLoader::new(config);
+        boot.prepare_boot(aligned_buf.as_mut()).expect("Boot prepare error");
+        Self
     }
 
     /// Boots the application.
@@ -41,8 +30,6 @@ impl<ACTIVE: NorFlash, DFU: NorFlash, STATE: NorFlash, const BUFFER_SIZE: usize>
     ///
     /// This modifies the stack pointer and reset vector and will run code placed in the active partition.
     pub unsafe fn load(self, start: u32) -> ! {
-        core::mem::drop(self.boot);
-
         trace!("Loading app at 0x{:x}", start);
         #[allow(unused_mut)]
         let mut p = cortex_m::Peripherals::steal();