From 1bbbadbc6a804f7b0c975eaf3a39d6f4bf1b3075 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20G=C3=B6ttgens?= <tgoettgens@gmail.com>
Date: Thu, 15 Oct 2026 17:31:18 +0200
Subject: [PATCH] Check the init packet before invalidating the application

The single-bank DFU erased bank 0 as soon as the start packet arrived and
checked the device type, revision and installed SoftDevice only later, with
the init packet. A package built for another SoftDevice was refused after the
application was already gone, leaving the board in the bootloader.

RRAM is written without an erase, so the bulk erase is dropped. The start
packet is acknowledged at once, and bank 0 is marked invalid in the settings
only after dfu_init_prevalidate() accepts the init packet. A refused package
now leaves the application in place.
---
 .../bootloader_dfu/dfu_single_bank.c          | 64 +++----------------
 1 file changed, 10 insertions(+), 54 deletions(-)

diff --git a/lib/sdk11/components/libraries/bootloader_dfu/dfu_single_bank.c b/lib/sdk11/components/libraries/bootloader_dfu/dfu_single_bank.c
index e64e472..3513c85 100644
--- a/lib/sdk11/components/libraries/bootloader_dfu/dfu_single_bank.c
+++ b/lib/sdk11/components/libraries/bootloader_dfu/dfu_single_bank.c
@@ -65,18 +65,6 @@ static void pstorage_callback_handler(pstorage_handle_t * p_handle,
             }
             break;
 
-        case PSTORAGE_CLEAR_OP_CODE:
-            if (m_dfu_state == DFU_STATE_PREPARING)
-            {
-                m_functions.cleared();
-                m_dfu_state = DFU_STATE_RDY;
-                if (m_data_pkt_cb != NULL)
-                {
-                    m_data_pkt_cb(START_PACKET, result, p_data);
-                }
-            }
-            break;
-
         default:
             break;
     }
@@ -124,45 +112,7 @@ static uint32_t dfu_timer_restart(void)
 }
 
 
-/**@brief   Function for preparing of flash before receiving SoftDevice image.
- *
- * @details This function will erase current application area to ensure sufficient amount of
- *          storage for the SoftDevice image. Upon erase complete a callback will be done.
- *          See \ref dfu_bank_prepare_t for further details.
- */
-static void dfu_prepare_func_app_erase(uint32_t image_size)
-{
-    mp_storage_handle_active = &m_storage_handle_app;
-
-    // Doing a SoftDevice update thus current application must be cleared to ensure enough space
-    // for new SoftDevice.
-    m_dfu_state = DFU_STATE_PREPARING;
-
-    if ( is_ota() )
-    {
-        uint32_t err_code;
-        while(1) {
-            err_code = pstorage_clear(&m_storage_handle_app, m_image_size);
-            if (err_code != NRF_ERROR_NO_MEM)
-                break;
-            // No space, wait until an entry in the queue is freed
-            while (NRF_ERROR_NOT_FOUND != proc_soc()) {
-                // nothing
-            }
-        }
-        APP_ERROR_CHECK(err_code);
-    }
-    else
-    {
-        flash_nrf5x_erase(DFU_BANK_0_REGION_START, m_image_size);
-
-        // invoke complete callback
-        pstorage_callback_handler(&m_storage_handle_app, PSTORAGE_CLEAR_OP_CODE, NRF_SUCCESS, NULL, 0);
-    }
-}
-
-
-/**@brief   Function for handling behaviour when clear operation has completed.
+/**@brief   Function for marking bank 0 invalid before the new image is written over it.
  */
 static void dfu_cleared_func_app(void)
 {
@@ -288,6 +238,7 @@ uint32_t dfu_init(void)
     }
 
     m_storage_handle_app.block_id  = DFU_BANK_0_REGION_START;
+    mp_storage_handle_active       = &m_storage_handle_app;
 
     // Create the timer to monitor the activity by the peer doing the firmware update.
     err_code = app_timer_create(&m_dfu_timer_id,
@@ -351,8 +302,6 @@ uint32_t dfu_start_pkt_handle(dfu_update_packet_t * p_packet)
     {
         return NRF_ERROR_DATA_SIZE;
     }
-    m_functions.prepare  = dfu_prepare_func_app_erase;
-    m_functions.cleared  = dfu_cleared_func_app;
 
     if (IS_UPDATING_SD(m_start_packet))
     {
@@ -373,7 +322,11 @@ uint32_t dfu_start_pkt_handle(dfu_update_packet_t * p_packet)
     err_code = dfu_timer_restart();
     VERIFY_SUCCESS(err_code);
 
-    m_functions.prepare(m_image_size);
+    m_dfu_state = DFU_STATE_RDY;
+    if (m_data_pkt_cb != NULL)
+    {
+        m_data_pkt_cb(START_PACKET, NRF_SUCCESS, NULL);
+    }
 
     return NRF_SUCCESS;
 }
@@ -481,6 +434,9 @@ uint32_t dfu_init_pkt_complete(void)
         err_code = dfu_init_prevalidate(m_init_packet, m_init_packet_length, m_start_packet.dfu_update_mode);
         if (err_code == NRF_SUCCESS)
         {
+            // RRAM is written without an erase, so the application stays intact until here: a package
+            // refused above (e.g. built for another SoftDevice) leaves the board able to boot it.
+            dfu_cleared_func_app();
             m_dfu_state = DFU_STATE_RX_DATA_PKT;
         }
         else