Have a way to get the booted partition (#3979)

* Have a way to get the booted partition

* CHANGELOG.md

* Add inline docs

esp-bootloader-esp-idf/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - `FlashRegion::partition_size` (#3902)
+- `PartitionTable::booted_partition`(#3979)
 
 ### Changed
 

esp-bootloader-esp-idf/src/partitions.rs

@@ -301,6 +301,48 @@ impl<'a> PartitionTable<'a> {
         }
         Ok(None)
     }
+
+    #[cfg(not(feature = "std"))]
+    /// Get the currently booted partition.
+    pub fn booted_partition(&self) -> Result<Option<PartitionEntry<'a>>, Error> {
+        // Read entry 0 from MMU to know which partition is mapped
+        //
+        // See <https://github.com/espressif/esp-idf/blob/758939caecb16e5542b3adfba0bc85025517db45/components/hal/mmu_hal.c#L124>
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "esp32")] {
+                let paddr = unsafe {
+                    ((0x3FF10000 as *const u32).read_volatile() & 0xff) << 16
+                };
+            } else if #[cfg(feature = "esp32s2")] {
+                let paddr = unsafe {
+                    (((0x61801000 + 128 * 4) as *const u32).read_volatile() & 0xff) << 16
+                };
+            } else if #[cfg(feature = "esp32s3")] {
+                // Revisit this once we support XiP from PSRAM for ESP32-S3
+                let paddr = unsafe {
+                    ((0x600C5000 as *const u32).read_volatile() & 0xff) << 16
+                };
+            } else if #[cfg(any(feature = "esp32c2", feature = "esp32c3"))] {
+                let paddr = unsafe {
+                    ((0x600c5000 as *const u32).read_volatile() & 0xff) << 16
+                };
+            } else if #[cfg(any(feature = "esp32c6", feature = "esp32h2"))] {
+                let paddr = unsafe {
+                    ((0x60002000 + 0x380) as *mut u32).write_volatile(0);
+                    (((0x60002000 + 0x37c) as *const u32).read_volatile() & 0xff) << 16
+                };
+            }
+        }
+
+        for id in 0..self.len() {
+            let entry = self.get_partition(id)?;
+            if entry.offset() == paddr {
+                return Ok(Some(entry));
+            }
+        }
+
+        Ok(None)
+    }
 }
 
 /// A partition type including the sub-type.

examples/ota/update/src/main.rs

@@ -66,6 +66,8 @@ fn main() -> ! {
         println!("{:?}", pt.get_partition(i));
     }
 
+    println!("Currently booted partition {:?}", pt.booted_partition());
+
     // Find the OTA-data partition and show the currently active partition
     let ota_part = pt
         .find_partition(esp_bootloader_esp_idf::partitions::PartitionType::Data(