boot/nuttx: add configuration for tertiary slot

This slot is used in newly introduced copy with revert algorithm. This
commit allows NuttX to support this algorithm.

Signed-off-by: Michal Lenc <michallenc@seznam.cz>

boot/nuttx/include/mcuboot_config/mcuboot_config.h

@@ -78,6 +78,16 @@
 #  define MCUBOOT_OVERWRITE_ONLY_FAST
 #endif
 
+/* Enable copy with revert algorithm. This algorithm uses three slots and
+ * always keep the current image in both primary and secondary or tertiary
+ * partitions. This way update can be done without swapping while keeping
+ * the ability to revert.
+ */
+
+#ifdef CONFIG_MCUBOOT_COPY_WITH_REVERT
+#  define MCUBOOT_COPY_WITH_REVERT
+#endif
+
 /* Enable the direct-xip code path. */
 
 #ifdef CONFIG_MCUBOOT_DIRECT_XIP

boot/nuttx/include/sysflash/sysflash.h

@@ -26,14 +26,18 @@
 
 #define PRIMARY_ID      0
 #define SECONDARY_ID    1
-#define SCRATCH_ID      2
+#define TERTIARY_ID     2
+#define SCRATCH_ID      3
 
 #define FLASH_AREA_IMAGE_PRIMARY(x)    (((x) == 0) ?        \
                                          PRIMARY_ID :       \
                                          PRIMARY_ID)
 #define FLASH_AREA_IMAGE_SECONDARY(x)  (((x) == 0) ?        \
                                          SECONDARY_ID :     \
                                          SECONDARY_ID)
+#define FLASH_AREA_IMAGE_TERTIARY(x)   (((x) == 0) ?        \
+                                         TERTIARY_ID :      \
+                                         TERTIARY_ID)
 #define FLASH_AREA_IMAGE_SCRATCH       SCRATCH_ID
 
 #endif /* __BOOT_NUTTX_INCLUDE_SYSFLASH_SYSFLASH_H */

boot/nuttx/src/flash_map_backend/flash_map_backend.c

@@ -123,6 +123,31 @@ static struct flash_device_s g_secondary_priv =
   .erase_state = CONFIG_MCUBOOT_DEFAULT_FLASH_ERASE_STATE
 };
 
+static struct flash_area g_tertiary_img0 =
+{
+  .fa_id = FLASH_AREA_IMAGE_TERTIARY(0),
+  .fa_device_id = 0,
+  .fa_off = 0,
+  .fa_size = 0,
+  .fa_mtd_path = CONFIG_MCUBOOT_TERTIARY_SLOT_PATH
+};
+
+static struct flash_device_s g_tertiary_priv =
+{
+  .fa_cfg = &g_tertiary_img0,
+  .mtdgeo =
+            {
+              0
+            },
+  .partinfo =
+              {
+                0
+              },
+  .fd = -1,
+  .refs = 0,
+  .erase_state = CONFIG_MCUBOOT_DEFAULT_FLASH_ERASE_STATE
+};
+
 static struct flash_area g_scratch_img0 =
 {
   .fa_id = FLASH_AREA_IMAGE_SCRATCH,
@@ -152,6 +177,7 @@ static struct flash_device_s *g_flash_devices[] =
 {
   &g_primary_priv,
   &g_secondary_priv,
+  &g_tertiary_priv,
   &g_scratch_priv,
 };
 
@@ -713,6 +739,8 @@ int flash_area_id_from_multi_image_slot(int image_index, int slot)
         return FLASH_AREA_IMAGE_PRIMARY(image_index);
       case 1:
         return FLASH_AREA_IMAGE_SECONDARY(image_index);
+      case 2:
+        return FLASH_AREA_IMAGE_TERTIARY(image_index);
     }
 
   BOOT_LOG_ERR("Unexpected Request: image_index:%d, slot:%d",