diff --git a/apps/buffering.c b/apps/buffering.c
index 0cb428c947..d49669777b 100644
--- a/apps/buffering.c
+++ b/apps/buffering.c
@@ -182,7 +182,7 @@ enum {
 };
 
 /* Buffering thread */
-void buffering_thread(void);
+static void buffering_thread(void);
 static long buffering_stack[(DEFAULT_STACK_SIZE + 0x2000)/sizeof(long)];
 static const char buffering_thread_name[] = "buffering";
 static struct thread_entry *buffering_thread_p;
@@ -190,7 +190,7 @@ static struct event_queue buffering_queue;
 static struct queue_sender_list buffering_queue_sender_list;
 
 
-static void call_buffering_callbacks(enum callback_event ev, int value);
+static void call_buffering_callbacks(const enum callback_event ev, const int value);
 
 
 /*
@@ -407,7 +407,7 @@ static struct memory_handle *find_handle(const int handle_id)
            found in the linked list for adjustment.  This function has no side
            effects if NULL is returned. */
 static bool move_handle(struct memory_handle **h, size_t *delta,
-                        const size_t data_size, bool can_wrap)
+                        const size_t data_size, const bool can_wrap)
 {
     struct memory_handle *dest;
     const struct memory_handle *src;
@@ -492,7 +492,7 @@ static bool move_handle(struct memory_handle **h, size_t *delta,
     if (overlap > 0) {
         size_t first_part = size_to_move - overlap;
         memmove(dest, src, first_part);
-        memmove(buffer, (char *)src + first_part, overlap);
+        memmove(buffer, (const char *)src + first_part, overlap);
     } else {
         memmove(dest, src, size_to_move);
     }
@@ -559,7 +559,7 @@ static inline bool buffer_is_low(void)
 
 /* Buffer data for the given handle.
    Return whether or not the buffering should continue explicitly.  */
-static bool buffer_handle(int handle_id)
+static bool buffer_handle(const int handle_id)
 {
     logf("buffer_handle(%d)", handle_id);
     struct memory_handle *h = find_handle(handle_id);
@@ -667,7 +667,7 @@ static bool buffer_handle(int handle_id)
 
 /* Reset writing position and data buffer of a handle to its current offset.
    Use this after having set the new offset to use. */
-static void reset_handle(int handle_id)
+static void reset_handle(const int handle_id)
 {
     logf("reset_handle(%d)", handle_id);
 
@@ -687,7 +687,7 @@ static void reset_handle(int handle_id)
 }
 
 /* Seek to a nonbuffered part of a handle by rebuffering the data. */
-static void rebuffer_handle(int handle_id, size_t newpos)
+static void rebuffer_handle(const int handle_id, const size_t newpos)
 {
     struct memory_handle *h = find_handle(handle_id);
     if (!h)
@@ -725,7 +725,7 @@ static void rebuffer_handle(int handle_id, size_t newpos)
     h->ridx = h->data;
 }
 
-static bool close_handle(int handle_id)
+static bool close_handle(const int handle_id)
 {
     struct memory_handle *h = find_handle(handle_id);
 
@@ -774,7 +774,7 @@ static void shrink_handle(struct memory_handle *h)
             /* when moving an mp3entry we need to readjust its pointers. */
             adjust_mp3entry((struct mp3entry *)&buffer[h->data],
                             (void *)&buffer[h->data],
-                            (void *)&buffer[olddata]);
+                            (const void *)&buffer[olddata]);
         } else if (h->type == TYPE_BITMAP) {
             /* adjust the bitmap's pointer */
             struct bitmap *bmp = (struct bitmap *)&buffer[h->data];
@@ -873,7 +873,7 @@ management functions for all the actual handle management work.
    return value: <0 if the file cannot be opened, or one file already
    queued to be opened, otherwise the handle for the file in the buffer
 */
-int bufopen(const char *file, size_t offset, enum data_type type)
+int bufopen(const char *file, size_t offset, const enum data_type type)
 {
     int fd = open(file, O_RDONLY);
     if (fd < 0)
@@ -955,7 +955,7 @@ int bufopen(const char *file, size_t offset, enum data_type type)
    requested amount of data can entirely fit in the buffer without wrapping.
    Return value is the handle id for success or <0 for failure.
 */
-int bufalloc(const void *src, size_t size, enum data_type type)
+int bufalloc(const void *src, const size_t size, const enum data_type type)
 {
     struct memory_handle *h = add_handle(size, false, true);
 
@@ -966,7 +966,7 @@ int bufalloc(const void *src, size_t size, enum data_type type)
         if (type == TYPE_ID3 && size == sizeof(struct mp3entry)) {
             /* specially take care of struct mp3entry */
             copy_mp3entry((struct mp3entry *)&buffer[buf_widx],
-                          (struct mp3entry *)src);
+                          (const struct mp3entry *)src);
         } else {
             memcpy(&buffer[buf_widx], src, size);
         }
@@ -990,7 +990,7 @@ int bufalloc(const void *src, size_t size, enum data_type type)
 }
 
 /* Close the handle. Return true for success and false for failure */
-bool bufclose(int handle_id)
+bool bufclose(const int handle_id)
 {
     logf("bufclose(%d)", handle_id);
 
@@ -1004,7 +1004,7 @@ bool bufclose(int handle_id)
      -1 if the handle wasn't found
      -2 if the new requested position was beyond the end of the file
 */
-int bufseek(int handle_id, size_t newpos)
+int bufseek(const int handle_id, const size_t newpos)
 {
     struct memory_handle *h = find_handle(handle_id);
     if (!h)
@@ -1026,7 +1026,7 @@ int bufseek(int handle_id, size_t newpos)
 
 /* Advance the reading index in a handle (relatively to its current position).
    Return 0 for success and < 0 for failure */
-int bufadvance(int handle_id, off_t offset)
+int bufadvance(const int handle_id, const off_t offset)
 {
     const struct memory_handle *h = find_handle(handle_id);
     if (!h)
@@ -1094,7 +1094,7 @@ static struct memory_handle *prep_bufdata(const int handle_id, size_t *size,
    Return the number of bytes copied or < 0 for failure (handle not found).
    The caller is blocked until the requested amount of data is available.
 */
-ssize_t bufread(int handle_id, size_t size, void *dest)
+ssize_t bufread(const int handle_id, size_t size, void *dest)
 {
     const struct memory_handle *h;
 
@@ -1126,7 +1126,7 @@ ssize_t bufread(int handle_id, size_t size, void *dest)
    The guard buffer may be used to provide the requested size. This means it's
    unsafe to request more than the size of the guard buffer.
 */
-ssize_t bufgetdata(int handle_id, size_t size, void **data)
+ssize_t bufgetdata(const int handle_id, size_t size, void **data)
 {
     const struct memory_handle *h;
 
@@ -1141,7 +1141,7 @@ ssize_t bufgetdata(int handle_id, size_t size, void **data)
         size_t copy_n = h->ridx + size - buffer_len;
         /* prep_bufdata ensures size <= buffer_len - h->ridx + GUARD_BUFSIZE,
            so copy_n <= GUARD_BUFSIZE */
-        memcpy(guard_buffer, (unsigned char *)buffer, copy_n);
+        memcpy(guard_buffer, (const unsigned char *)buffer, copy_n);
     }
 
     if (data)
@@ -1150,7 +1150,7 @@ ssize_t bufgetdata(int handle_id, size_t size, void **data)
     return size;
 }
 
-ssize_t bufgettail(int handle_id, size_t size, void **data)
+ssize_t bufgettail(const int handle_id, const size_t size, void **data)
 {
     size_t tidx;
 
@@ -1173,14 +1173,14 @@ ssize_t bufgettail(int handle_id, size_t size, void **data)
     if (tidx + size > buffer_len)
     {
         size_t copy_n = tidx + size - buffer_len;
-        memcpy(guard_buffer, (unsigned char *)buffer, copy_n);
+        memcpy(guard_buffer, (const unsigned char *)buffer, copy_n);
     }
 
     *data = &buffer[tidx];
     return size;
 }
 
-ssize_t bufcuttail(int handle_id, size_t size)
+ssize_t bufcuttail(const int handle_id, size_t size)
 {
     struct memory_handle *h;
 
@@ -1198,9 +1198,9 @@ ssize_t bufcuttail(int handle_id, size_t size)
     h->available -= size;
     h->filesize -= size;
     h->widx = RINGBUF_SUB(h->widx, size);
-    if (h == cur_handle) {
+    if (h == cur_handle)
         buf_widx = h->widx;
-    }
+
     return size;
 }
 
@@ -1223,7 +1223,7 @@ management functions for all the actual handle management work.
 */
 
 /* Get a handle offset from a pointer */
-ssize_t buf_get_offset(int handle_id, void *ptr)
+ssize_t buf_get_offset(const int handle_id, void *ptr)
 {
     const struct memory_handle *h = find_handle(handle_id);
     if (!h)
@@ -1232,7 +1232,7 @@ ssize_t buf_get_offset(int handle_id, void *ptr)
     return (size_t)ptr - (size_t)&buffer[h->ridx];
 }
 
-ssize_t buf_handle_offset(int handle_id)
+ssize_t buf_handle_offset(const int handle_id)
 {
     const struct memory_handle *h = find_handle(handle_id);
     if (!h)
@@ -1240,13 +1240,13 @@ ssize_t buf_handle_offset(int handle_id)
     return h->offset;
 }
 
-void buf_request_buffer_handle(int handle_id)
+void buf_request_buffer_handle(const int handle_id)
 {
     LOGFQUEUE("buffering >| Q_START_FILL %d",handle_id);
     queue_send(&buffering_queue, Q_START_FILL, handle_id);
 }
 
-void buf_set_base_handle(int handle_id)
+void buf_set_base_handle(const int handle_id)
 {
     LOGFQUEUE("buffering > Q_BASE_HANDLE %d", handle_id);
     queue_post(&buffering_queue, Q_BASE_HANDLE, handle_id);
@@ -1258,13 +1258,13 @@ size_t buf_used(void)
     return BUF_USED;
 }
 
-void buf_set_watermark(size_t bytes)
+void buf_set_watermark(const size_t bytes)
 {
     LOGFQUEUE("buffering > Q_SET_WATERMARK %ld", (long)bytes);
     queue_post(&buffering_queue, Q_SET_WATERMARK, bytes);
 }
 
-bool register_buffering_callback(buffering_callback func)
+bool register_buffering_callback(const buffering_callback func)
 {
     int i;
     if (buffer_callback_count >= MAX_BUF_CALLBACKS)
@@ -1283,7 +1283,7 @@ bool register_buffering_callback(buffering_callback func)
     return false;
 }
 
-void unregister_buffering_callback(buffering_callback func)
+void unregister_buffering_callback(const buffering_callback func)
 {
     int i;
     for (i = 0; i < MAX_BUF_CALLBACKS; i++)
@@ -1297,7 +1297,7 @@ void unregister_buffering_callback(buffering_callback func)
     return;
 }
 
-static void call_buffering_callbacks(enum callback_event ev, int value)
+static void call_buffering_callbacks(const enum callback_event ev, const int value)
 {
     logf("call_buffering_callbacks()");
     int i;
@@ -1310,8 +1310,8 @@ static void call_buffering_callbacks(enum callback_event ev, int value)
     }
 }
 
-static void shrink_buffer_inner(struct memory_handle *h) {
-
+static void shrink_buffer_inner(struct memory_handle *h)
+{
     if (h == NULL)
         return;
 
@@ -1320,7 +1320,8 @@ static void shrink_buffer_inner(struct memory_handle *h) {
     shrink_handle(h);
 }
 
-static void shrink_buffer(void) {
+static void shrink_buffer(void)
+{
     logf("shrink_buffer()");
     shrink_buffer_inner(first_handle);
 }
@@ -1444,7 +1445,8 @@ void buffering_thread(void)
     }
 }
 
-void buffering_init(void) {
+void buffering_init(void)
+{
     mutex_init(&llist_mutex);
 #ifdef HAVE_PRIORITY_SCHEDULING
     /* This behavior not safe atm */
@@ -1464,7 +1466,7 @@ void buffering_init(void) {
 }
 
 /* Initialise the buffering subsystem */
-bool buffering_reset(char *buf, size_t buflen)
+bool buffering_reset(char *buf, const size_t buflen)
 {
     if (!buf || !buflen)
         return false;
diff --git a/apps/buffering.h b/apps/buffering.h
index bc61ec5e6d..abe8f608c6 100644
--- a/apps/buffering.h
+++ b/apps/buffering.h
@@ -56,7 +56,7 @@ enum callback_event {
 void buffering_init(void);
 
 /* Reset the buffering system */
-bool buffering_reset(char *buf, size_t buflen);
+bool buffering_reset(char *buf, const size_t buflen);
 
 
 /***************************************************************************
@@ -80,15 +80,15 @@ bool buffering_reset(char *buf, size_t buflen);
 
 #define BUF_MAX_HANDLES         256
 
-int bufopen(const char *file, size_t offset, enum data_type type);
-int bufalloc(const void *src, size_t size, enum data_type type);
-bool bufclose(int handle_id);
-int bufseek(int handle_id, size_t newpos);
-int bufadvance(int handle_id, off_t offset);
-ssize_t bufread(int handle_id, size_t size, void *dest);
-ssize_t bufgetdata(int handle_id, size_t size, void **data);
-ssize_t bufgettail(int handle_id, size_t size, void **data);
-ssize_t bufcuttail(int handle_id, size_t size);
+int bufopen(const char *file, size_t offset, const enum data_type type);
+int bufalloc(const void *src, const size_t size, const enum data_type type);
+bool bufclose(const int handle_id);
+int bufseek(const int handle_id, const size_t newpos);
+int bufadvance(const int handle_id, const off_t offset);
+ssize_t bufread(const int handle_id, size_t size, void *dest);
+ssize_t bufgetdata(const int handle_id, size_t size, void **data);
+ssize_t bufgettail(const int handle_id, const size_t size, void **data);
+ssize_t bufcuttail(const int handle_id, size_t size);
 
 
 /***************************************************************************
@@ -102,10 +102,10 @@ ssize_t bufcuttail(int handle_id, size_t size);
  * buf_used: Total amount of buffer space used (including allocated space)
  ****************************************************************************/
 
-ssize_t buf_get_offset(int handle_id, void *ptr);
-ssize_t buf_handle_offset(int handle_id);
-void buf_request_buffer_handle(int handle_id);
-void buf_set_base_handle(int handle_id);
+ssize_t buf_get_offset(const int handle_id, void *ptr);
+ssize_t buf_handle_offset(const int handle_id);
+void buf_request_buffer_handle(const int handle_id);
+void buf_set_base_handle(const int handle_id);
 size_t buf_used(void);
 
 
@@ -123,9 +123,9 @@ size_t buf_used(void);
  ****************************************************************************/
 
 #define MAX_BUF_CALLBACKS 4
-typedef void (*buffering_callback)(enum callback_event ev, int value);
-bool register_buffering_callback(buffering_callback func);
-void unregister_buffering_callback(buffering_callback func);
+typedef void (*buffering_callback)(const enum callback_event ev, const int value);
+bool register_buffering_callback(const buffering_callback func);
+void unregister_buffering_callback(const buffering_callback func);
 
 /* Settings */
 enum {
diff --git a/apps/plugin.h b/apps/plugin.h
index 66ed5fdbb2..27fcffb69c 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -120,12 +120,12 @@
 #define PLUGIN_MAGIC 0x526F634B /* RocK */
 
 /* increase this every time the api struct changes */
-#define PLUGIN_API_VERSION 103
+#define PLUGIN_API_VERSION 104
 
 /* update this to latest version if a change to the api struct breaks
    backwards compatibility (and please take the opportunity to sort in any
    new function which are "waiting" at the end of the function table) */
-#define PLUGIN_MIN_API_VERSION 103
+#define PLUGIN_MIN_API_VERSION 104
 
 /* plugin return codes */
 enum plugin_status {
@@ -684,20 +684,20 @@ struct plugin_api {
 
 #if (CONFIG_CODEC == SWCODEC)
     /* buffering API */
-    int (*bufopen)(const char *file, size_t offset, enum data_type type);
-    int (*bufalloc)(const void *src, size_t size, enum data_type type);
-    bool (*bufclose)(int handle_id);
-    int (*bufseek)(int handle_id, size_t newpos);
-    int (*bufadvance)(int handle_id, off_t offset);
-    ssize_t (*bufread)(int handle_id, size_t size, void *dest);
-    ssize_t (*bufgetdata)(int handle_id, size_t size, void **data);
-    ssize_t (*bufgettail)(int handle_id, size_t size, void **data);
-    ssize_t (*bufcuttail)(int handle_id, size_t size);
+    int (*bufopen)(const char *file, size_t offset, const enum data_type type);
+    int (*bufalloc)(const void *src, const size_t size, const enum data_type type);
+    bool (*bufclose)(const int handle_id);
+    int (*bufseek)(const int handle_id, const size_t newpos);
+    int (*bufadvance)(const int handle_id, const off_t offset);
+    ssize_t (*bufread)(const int handle_id, size_t size, void *dest);
+    ssize_t (*bufgetdata)(const int handle_id, size_t size, void **data);
+    ssize_t (*bufgettail)(const int handle_id, const size_t size, void **data);
+    ssize_t (*bufcuttail)(const int handle_id, size_t size);
 
-    ssize_t (*buf_get_offset)(int handle_id, void *ptr);
-    ssize_t (*buf_handle_offset)(int handle_id);
-    void (*buf_request_buffer_handle)(int handle_id);
-    void (*buf_set_base_handle)(int handle_id);
+    ssize_t (*buf_get_offset)(const int handle_id, void *ptr);
+    ssize_t (*buf_handle_offset)(const int handle_id);
+    void (*buf_request_buffer_handle)(const int handle_id);
+    void (*buf_set_base_handle)(const int handle_id);
     size_t (*buf_used)(void);
 #endif
 
diff --git a/firmware/export/id3.h b/firmware/export/id3.h
index bb3b6a6fe5..0035fae19a 100644
--- a/firmware/export/id3.h
+++ b/firmware/export/id3.h
@@ -234,7 +234,7 @@ bool mp3info(struct mp3entry *entry, const char *filename);
 char* id3_get_num_genre(const unsigned int genre_num);
 char* id3_get_codec(const struct mp3entry* id3);
 int getid3v2len(int fd);
-void adjust_mp3entry(struct mp3entry *entry, void *dest, void *orig);
-void copy_mp3entry(struct mp3entry *dest, struct mp3entry *orig);
+void adjust_mp3entry(struct mp3entry *entry, void *dest, const void *orig);
+void copy_mp3entry(struct mp3entry *dest, const struct mp3entry *orig);
 
 #endif
diff --git a/firmware/id3.c b/firmware/id3.c
index f594528910..6afe2ac304 100644
--- a/firmware/id3.c
+++ b/firmware/id3.c
@@ -1231,7 +1231,7 @@ bool mp3info(struct mp3entry *entry, const char *filename)
     return result;
 }
 
-void adjust_mp3entry(struct mp3entry *entry, void *dest, void *orig)
+void adjust_mp3entry(struct mp3entry *entry, void *dest, const void *orig)
 {
     long offset;
     if (orig > dest)
@@ -1270,7 +1270,7 @@ void adjust_mp3entry(struct mp3entry *entry, void *dest, void *orig)
 #endif
 }
 
-void copy_mp3entry(struct mp3entry *dest, struct mp3entry *orig)
+void copy_mp3entry(struct mp3entry *dest, const struct mp3entry *orig)
 {
     memcpy(dest, orig, sizeof(struct mp3entry));
     adjust_mp3entry(dest, dest, orig);