fixup! sys/riotboot: add helper functions for riotboot VFS

sys/riotboot/vfs.c

@@ -25,12 +25,13 @@
 #include "periph/flashpage.h"
 #include "riotboot/vfs.h"
 
-static const void *_first_free_page(const void *start)
+/* try to guess the end of the firmware */
+static const void *_first_free_chunk(const void *start)
 {
     const uword_t *cur = start;
     const uword_t *end = flashpage_addr(FLASHPAGE_NUMOF);
     uword_t empty;
-    unsigned i = flashpage_page(start);
+    unsigned const chunk_size = 256;
     memset(&empty, FLASHPAGE_ERASE_STATE, sizeof(empty));
 
     /* try to find the first unused page */
@@ -39,7 +40,7 @@ static const void *_first_free_page(const void *start)
             cur[2] == empty && cur[3] == empty) {
             break;
         }
-        cur += flashpage_size(i++);
+        cur += chunk_size;
     }
 
     return cur;
@@ -51,7 +52,7 @@ int riotboot_vfs_dump_rom(const char* file)
 
     if (IS_ACTIVE(RIOTBOOT)) {
         start = (void *)(uintptr_t)SLOT0_OFFSET;
-        end   = _first_free_page(start);
+        end   = _first_free_chunk(start);
     } else {
         start = flashpage_addr(flashpage_first_used());
         end   = flashpage_addr(flashpage_first_free());