3 files changed, 18 insertions, 9 deletions
diff --git a/shared-module/msgpack/__init__.c b/shared-module/msgpack/__init__.c
index 39178d46e..103003174 100644
--- a/shared-module/msgpack/__init__.c
+++ b/shared-module/msgpack/__init__.c
@@ -255,11 +255,6 @@ STATIC void pack(mp_obj_t obj, msgpack_stream_t *s, mp_obj_t default_handler) {
         mp_buffer_info_t bufinfo;
         mp_get_buffer_raise(ext->data, &bufinfo, MP_BUFFER_READ);
         pack_ext(s, ext->code, bufinfo.buf, bufinfo.len);
-    } else if (MP_OBJ_IS_TYPE(obj, &mp_type_bytes)) {
-        // bytes
-        mp_buffer_info_t bufinfo;
-        mp_get_buffer_raise(obj, &bufinfo, MP_BUFFER_READ);
-        pack_bin(s, bufinfo.buf, bufinfo.len);
     } else if (MP_OBJ_IS_TYPE(obj, &mp_type_tuple)) {
         // tuple
         mp_obj_tuple_t *self = MP_OBJ_TO_PTR(obj);
@@ -297,7 +292,11 @@ STATIC void pack(mp_obj_t obj, msgpack_stream_t *s, mp_obj_t default_handler) {
     } else if (obj == mp_const_true) {
         write1(s, 0xc3);
     } else {
-        if (default_handler != mp_const_none) {
+        mp_buffer_info_t bufinfo;
+        if (mp_get_buffer(obj, &bufinfo, MP_BUFFER_READ)) {
+            // bytes (bin type)
+            pack_bin(s, bufinfo.buf, bufinfo.len);
+        } else if (default_handler != mp_const_none) {
             // set default_handler to mp_const_none to avoid infinite recursion
             // this also precludes some valid outputs
             pack(mp_call_function_1(default_handler, obj), s, mp_const_none);
@@ -332,7 +331,15 @@ STATIC mp_obj_t unpack_bytes(msgpack_stream_t *s, size_t size) {
     vstr_t vstr;
     vstr_init_len(&vstr, size);
     byte *p = (byte*)vstr.buf;
-    read(s, p, size);
+    // read in chunks: (some drivers - e.g. UART) limit the
+    // maximum number of bytes that can be read at once
+    // read(s, p, size);
+    while (size > 0) {
+        int n = size > 256 ? 256 : size;
+        read(s, p, n);
+        size -= n;
+        p += n;
+    }
     return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }
 
diff --git a/shared-module/os/__init__.c b/shared-module/os/__init__.c
index 39cf40fda..159b54e31 100644
--- a/shared-module/os/__init__.c
+++ b/shared-module/os/__init__.c
@@ -42,6 +42,7 @@
 // Version of mp_vfs_lookup_path that takes and returns uPy string objects.
 STATIC mp_vfs_mount_t *lookup_path(const char* path, mp_obj_t *path_out) {
     const char *p_out;
+    *path_out = mp_const_none;
     mp_vfs_mount_t *vfs = mp_vfs_lookup_path(path, &p_out);
     if (vfs != MP_VFS_NONE && vfs != MP_VFS_ROOT) {
         *path_out = mp_obj_new_str_of_type(&mp_type_str,
@@ -53,6 +54,7 @@ STATIC mp_vfs_mount_t *lookup_path(const char* path, mp_obj_t *path_out) {
 // Strip off trailing slashes to please underlying libraries
 STATIC mp_vfs_mount_t *lookup_dir_path(const char* path, mp_obj_t *path_out) {
     const char *p_out;
+    *path_out = mp_const_none;
     mp_vfs_mount_t *vfs = mp_vfs_lookup_path(path, &p_out);
     if (vfs != MP_VFS_NONE && vfs != MP_VFS_ROOT) {
         size_t len = strlen(p_out);
diff --git a/shared-module/sdcardio/SDCard.c b/shared-module/sdcardio/SDCard.c
index 9e861279d..1712f58ee 100644
--- a/shared-module/sdcardio/SDCard.c
+++ b/shared-module/sdcardio/SDCard.c
@@ -375,7 +375,7 @@ int common_hal_sdcardio_sdcard_readblocks(sdcardio_sdcard_obj_t *self, uint32_t
     return r;
 }
 
-int _write(sdcardio_sdcard_obj_t *self, uint8_t token, void *buf, size_t size) {
+STATIC int _write(sdcardio_sdcard_obj_t *self, uint8_t token, void *buf, size_t size) {
     wait_for_ready(self);
 
     uint8_t cmd[2];
@@ -420,7 +420,7 @@ int _write(sdcardio_sdcard_obj_t *self, uint8_t token, void *buf, size_t size) {
     return 0;
 }
 
-int writeblocks(sdcardio_sdcard_obj_t *self, uint32_t start_block, mp_buffer_info_t *buf) {
+STATIC int writeblocks(sdcardio_sdcard_obj_t *self, uint32_t start_block, mp_buffer_info_t *buf) {
     common_hal_sdcardio_check_for_deinit(self);
     uint32_t nblocks = buf->len / 512;
     if (nblocks == 1) {