diff --git a/apps/plugin.h b/apps/plugin.h
index 8ee2534372..d44aa7d60b 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -112,7 +112,7 @@ struct plugin_api {
     /* lcd */
     void (*lcd_clear_display)(void);
     void (*lcd_puts)(int x, int y, const unsigned char *string);
-    void (*lcd_puts_scroll)(int x, int y, unsigned char* string);
+    void (*lcd_puts_scroll)(int x, int y, const unsigned char* string);
     void (*lcd_stop_scroll)(void);
     void (*lcd_set_contrast)(int x);
 #ifdef HAVE_LCD_CHARCELLS
@@ -211,7 +211,7 @@ struct plugin_api {
     /* sound */
     void (*mpeg_sound_set)(int setting, int value);
 #ifndef SIMULATOR
-    void (*mp3_play_data)(unsigned char* start, int size, void (*get_more)(unsigned char** start, int* size));
+    void (*mp3_play_data)(const unsigned char* start, int size, void (*get_more)(unsigned char** start, int* size));
     void (*mp3_play_pause)(bool play);
     void (*mp3_play_stop)(void);
     bool (*mp3_is_playing)(void);
@@ -264,7 +264,7 @@ struct plugin_api {
 #endif
     struct user_settings* global_settings;
     void (*backlight_set_timeout)(int index);
-    bool (*mp3info)(struct mp3entry *entry, char *filename, bool v1first);
+    bool (*mp3info)(struct mp3entry *entry, const char *filename, bool v1first);
     int (*count_mp3_frames)(int fd, int startpos, int filesize,
                             void (*progressfunc)(int));
     int (*create_xing_header)(int fd, int startpos, int filesize,
@@ -285,7 +285,8 @@ struct plugin_api {
     int  (*peak_meter_get_use_dbfs)(void);
 #endif
 #ifdef HAVE_LCD_BITMAP
-    void (*lcd_puts_scroll_style)(int x, int y, unsigned char* string, int style);
+    void (*lcd_puts_scroll_style)(int x, int y, const unsigned char* string,
+                                  int style);
 #endif
    void (*mpeg_flush_and_reload_tracks)(void);
    int (*strncasecmp)(const char *s1, const char *s2, size_t n);
diff --git a/firmware/debug.c b/firmware/debug.c
index 977ece3f5d..6a30c6076a 100644
--- a/firmware/debug.c
+++ b/firmware/debug.c
@@ -112,11 +112,11 @@ static char lowhex(int  x)
    return hexchars[x & 0xf];
 }
 
-static void putpacket (char *buffer)
+static void putpacket (const char *buffer)
 {
     register  int checksum;
 
-    char *src = buffer;
+    const char *src = buffer;
 
    /* Special debug hack. Shut off the Rx IRQ during I/O to prevent the debug
       stub from interrupting the message */
@@ -172,7 +172,7 @@ static void putpacket (char *buffer)
 
 /* convert the memory, pointed to by mem into hex, placing result in buf */
 /* return a pointer to the last char put in buf (null) */
-static char *mem2hex (char *mem, char *buf, int count)
+static char *mem2hex (const char *mem, char *buf, int count)
 {
     int i;
     int ch;
@@ -186,7 +186,7 @@ static char *mem2hex (char *mem, char *buf, int count)
     return (buf);
 }
 
-static void debug(char *msg)
+static void debug(const char *msg)
 {
     debugbuf[0] = 'O';
     
@@ -196,7 +196,7 @@ static void debug(char *msg)
 #endif /* end of DEBUG section */
 
 #ifdef __GNUC__
-void debugf(char *fmt, ...)
+void debugf(const char *fmt, ...)
 #endif
 {
 #ifdef DEBUG
@@ -218,7 +218,7 @@ void debug_init(void)
 {
 }
 
-void debugf(char *fmt, ...)
+void debugf(const char *fmt, ...)
 {
     va_list ap;
     va_start( ap, fmt );
@@ -226,7 +226,7 @@ void debugf(char *fmt, ...)
     va_end( ap );
 }
 
-void ldebugf(char* file, int line, char *fmt, ...)
+void ldebugf(const char* file, int line, const char *fmt, ...)
 {
     va_list ap;
     va_start( ap, fmt );
diff --git a/firmware/drivers/lcd-player.c b/firmware/drivers/lcd-player.c
index c948f49828..d4a523afe3 100644
--- a/firmware/drivers/lcd-player.c
+++ b/firmware/drivers/lcd-player.c
@@ -530,7 +530,7 @@ void lcd_bidir_scroll(int percent)
     bidir_limit = percent;
 }
 
-void lcd_puts_scroll(int x, int y, unsigned char* string )
+void lcd_puts_scroll(int x, int y, const unsigned char* string )
 {
     struct scrollinfo* s;
     int i;
diff --git a/firmware/drivers/lcd-recorder.c b/firmware/drivers/lcd-recorder.c
index 42cf016f97..a8dca92b4f 100644
--- a/firmware/drivers/lcd-recorder.c
+++ b/firmware/drivers/lcd-recorder.c
@@ -784,12 +784,12 @@ void lcd_invertpixel(int x, int y)
     INVERT_PIXEL(x,y);
 }
 
-void lcd_puts_scroll(int x, int y, unsigned char *string)
+void lcd_puts_scroll(int x, int y, const unsigned char *string)
 {
     lcd_puts_scroll_style(x, y, string, STYLE_DEFAULT);
 }
 
-void lcd_puts_scroll_style(int x, int y, unsigned char *string, int style)
+void lcd_puts_scroll_style(int x, int y, const unsigned char *string, int style)
 {
     struct scrollinfo* s;
     int w, h;
diff --git a/firmware/export/font.h b/firmware/export/font.h
index f2f83e54c8..14a683a5f2 100644
--- a/firmware/export/font.h
+++ b/firmware/export/font.h
@@ -103,7 +103,7 @@ struct font {
 
 /* font routines*/
 void font_init(void);
-struct font* font_load(char *path);
+struct font* font_load(const char *path);
 struct font* font_get(int font);
 void font_reset(void);
 
diff --git a/firmware/export/id3.h b/firmware/export/id3.h
index 10f8002db6..8a79cb0ce1 100644
--- a/firmware/export/id3.h
+++ b/firmware/export/id3.h
@@ -74,7 +74,7 @@ enum {
     ID3_VER_2_4
 };
 
-bool mp3info(struct mp3entry *entry, char *filename, bool v1first);
-char* id3_get_genre(struct mp3entry* id3);
+bool mp3info(struct mp3entry *entry, const char *filename, bool v1first);
+char* id3_get_genre(const struct mp3entry* id3);
 
 #endif
diff --git a/firmware/export/kernel.h b/firmware/export/kernel.h
index 6e11baedf6..97994c41df 100644
--- a/firmware/export/kernel.h
+++ b/firmware/export/kernel.h
@@ -71,7 +71,7 @@ extern void queue_init(struct event_queue *q);
 extern void queue_wait(struct event_queue *q, struct event *ev);
 extern void queue_wait_w_tmo(struct event_queue *q, struct event *ev, int ticks);
 extern void queue_post(struct event_queue *q, int id, void *data);
-extern bool queue_empty(struct event_queue* q);
+extern bool queue_empty(const struct event_queue* q);
 extern int queue_broadcast(int id, void *data);
 
 extern void mutex_init(struct mutex *m);
diff --git a/firmware/export/lcd.h b/firmware/export/lcd.h
index 6a7f8cf155..2a8a7ff0b1 100644
--- a/firmware/export/lcd.h
+++ b/firmware/export/lcd.h
@@ -35,8 +35,8 @@ extern void lcd_puts(int x, int y, const unsigned char *string);
 extern void lcd_puts_style(int x, int y, const unsigned char *string, int style);
 extern void lcd_putc(int x, int y, unsigned short ch);
 
-extern void lcd_puts_scroll(int x, int y, unsigned char* string );
-extern void lcd_puts_scroll_style(int x, int y, unsigned char* string,
+extern void lcd_puts_scroll(int x, int y, const unsigned char* string );
+extern void lcd_puts_scroll_style(int x, int y, const unsigned char* string,
                                   int style);
 extern void lcd_icon(int icon, bool enable);
 extern void lcd_stop_scroll(void);
diff --git a/firmware/export/mp3_playback.h b/firmware/export/mp3_playback.h
index 9eb1d882ff..12ef734bfe 100644
--- a/firmware/export/mp3_playback.h
+++ b/firmware/export/mp3_playback.h
@@ -51,7 +51,7 @@ void demand_irq_enable(bool on);
 
 /* new functions, exported to plugin API */
 void mp3_play_init(void);
-void mp3_play_data(unsigned char* start, int size,
+void mp3_play_data(const unsigned char* start, int size,
     void (*get_more)(unsigned char** start, int* size) /* callback fn */
 );
 void mp3_play_pause(bool play);
diff --git a/firmware/export/mpeg.h b/firmware/export/mpeg.h
index bf16a2ac73..3088dc5ffd 100644
--- a/firmware/export/mpeg.h
+++ b/firmware/export/mpeg.h
@@ -77,8 +77,8 @@ int mpeg_status(void);
 #if defined(HAVE_MAS3587F) || defined(SIMULATOR)
 void mpeg_init_recording(void);
 void mpeg_init_playback(void);
-void mpeg_record(char *filename);
-void mpeg_new_file(char *filename);
+void mpeg_record(const char *filename);
+void mpeg_new_file(const char *filename);
 void mpeg_set_recording_options(int frequency, int quality,
                                 int source, int channel_mode,
                                 bool editable, int prerecord_time);
diff --git a/firmware/export/panic.h b/firmware/export/panic.h
index 585f827927..fd63687606 100644
--- a/firmware/export/panic.h
+++ b/firmware/export/panic.h
@@ -20,6 +20,6 @@
 #ifndef __PANIC_H__
 #define __PANIC_H__
 
-void panicf( char *fmt, ... );
+void panicf( const char *fmt, ... );
 
 #endif /* __PANIC_H__ */
diff --git a/firmware/font.c b/firmware/font.c
index f33490869a..343dd0b278 100644
--- a/firmware/font.c
+++ b/firmware/font.c
@@ -53,9 +53,9 @@ static unsigned char *freeptr = mbuf;
 static unsigned char *fileptr;
 static unsigned char *eofptr;
 
-static void rotate_font_bits(struct font* pf);
+static void rotate_font_bits(const struct font* pf);
 static void rotleft(unsigned char *dst, 
-                    bitmap_t *src, 
+                    const bitmap_t *src,
                     unsigned int width,
                     unsigned int height);
 
@@ -120,7 +120,7 @@ void font_reset(void)
 }
 
 /* read and load font into incore font structure*/
-struct font* font_load(char *path)
+struct font* font_load(const char *path)
 {
     int fd, filesize;
     unsigned short maxwidth, height, ascent, pad;
@@ -263,7 +263,7 @@ struct font* font_get(int font)
 }
 
 /* convert font bitmap data inplace to rockbox format*/
-static void rotate_font_bits(struct font* pf)
+static void rotate_font_bits(const struct font* pf)
 {
     int i;
     unsigned long defaultchar = pf->defaultchar - pf->firstchar;
@@ -305,8 +305,8 @@ static void rotate_font_bits(struct font* pf)
  * Doing it this way keeps fonts in standard formats,
  * as well as keeping Rockbox hw bitmap format.
  */
-static void rotleft(unsigned char *dst, bitmap_t *src, unsigned int width,
-                    unsigned int height)
+static void rotleft(unsigned char *dst, const bitmap_t *src,
+                    unsigned int width, unsigned int height)
 {
     unsigned int i,j;
     unsigned int src_words;        /* # words of input image*/
diff --git a/firmware/id3.c b/firmware/id3.c
index 0a08fa0de8..4297c8ba70 100644
--- a/firmware/id3.c
+++ b/firmware/id3.c
@@ -77,7 +77,7 @@ static const char* const genres[] = {
     "Duet", "Punk Rock", "Drum Solo", "A capella", "Euro-House", "Dance Hall"
 };
 
-char* id3_get_genre(struct mp3entry* id3)
+char* id3_get_genre(const struct mp3entry* id3)
 {
     if( id3->genre_string )
         return id3->genre_string ;
@@ -799,7 +799,7 @@ static int getsonglength(int fd, struct mp3entry *entry)
  * about an MP3 file and updates it's entry accordingly.
  *
  */
-bool mp3info(struct mp3entry *entry, char *filename, bool v1first)
+bool mp3info(struct mp3entry *entry, const char *filename, bool v1first)
 {
     int fd;
     int v1found = false;
diff --git a/firmware/kernel.c b/firmware/kernel.c
index ec2c149cc5..2cb87ccbc9 100644
--- a/firmware/kernel.c
+++ b/firmware/kernel.c
@@ -126,7 +126,7 @@ void queue_post(struct event_queue *q, int id, void *data)
     set_irq_level(oldlevel);
 }
 
-bool queue_empty(struct event_queue* q)
+bool queue_empty(const struct event_queue* q)
 {
     return ( q->read == q->write );
 }
diff --git a/firmware/mp3_playback.c b/firmware/mp3_playback.c
index 1d4f77bf41..8159c4504c 100644
--- a/firmware/mp3_playback.c
+++ b/firmware/mp3_playback.c
@@ -1059,7 +1059,7 @@ void mp3_play_init(void)
     mp3_reset_playtime();
 }
 
-void mp3_play_data(unsigned char* start, int size,
+void mp3_play_data(const unsigned char* start, int size,
     void (*get_more)(unsigned char** start, int* size) /* callback fn */
 )
 {
diff --git a/firmware/mpeg.c b/firmware/mpeg.c
index c6afbd8e6c..bfcdfc1c0c 100644
--- a/firmware/mpeg.c
+++ b/firmware/mpeg.c
@@ -803,7 +803,7 @@ static void transfer_end(unsigned char** ppbuf, int* psize)
     wake_up_thread();
 }
 
-static int add_track_to_tag_list(char *filename)
+static int add_track_to_tag_list(const char *filename)
 {
     struct id3tag *t = NULL;
     int i;
@@ -938,7 +938,7 @@ static void track_change(void)
 }
 
 #ifdef DEBUG
-void hexdump(unsigned char *buf, int len)
+void hexdump(const unsigned char *buf, int len)
 {
     int i;
 
@@ -2167,7 +2167,7 @@ static void init_recording(void)
        call mpeg_set_recording_options(). */
 }
 
-void mpeg_record(char *filename)
+void mpeg_record(const char *filename)
 {
     mpeg_errno = 0;
     
@@ -2396,7 +2396,7 @@ void mpeg_set_recording_gain(int left, int right, bool use_mic)
                        0x0007);
 }
 
-void mpeg_new_file(char *filename)
+void mpeg_new_file(const char *filename)
 {
     mpeg_errno = 0;
     
diff --git a/firmware/panic.c b/firmware/panic.c
index df8afdfda3..147ee6292e 100644
--- a/firmware/panic.c
+++ b/firmware/panic.c
@@ -31,7 +31,7 @@ static char panic_buf[128];
 /*
  * "Dude. This is pretty fucked-up, right here." 
  */
-void panicf( char *fmt, ...)
+void panicf( const char *fmt, ...)
 {
     va_list ap;
 
diff --git a/firmware/rolo.c b/firmware/rolo.c
index c5cfc5d77b..d78078cdd7 100644
--- a/firmware/rolo.c
+++ b/firmware/rolo.c
@@ -30,7 +30,7 @@
 
 #define IRQ0_EDGE_TRIGGER 0x80
 
-static void rolo_error(char *text)
+static void rolo_error(const char *text)
 {
     lcd_clear_display();
     lcd_puts(0, 0, "ROLO error:");
@@ -43,8 +43,10 @@ static void rolo_error(char *text)
 }
 
 /* these are in assembler file "descramble.S" */
-extern unsigned short descramble(unsigned char* source, unsigned char* dest, int length);
-extern void rolo_restart(unsigned char* source, unsigned char* dest, int length);
+extern unsigned short descramble(const unsigned char* source,
+                                 unsigned char* dest, int length);
+extern void rolo_restart(const unsigned char* source, unsigned char* dest,
+                         int length);
 
 /***************************************************************************
  *
@@ -52,7 +54,7 @@ extern void rolo_restart(unsigned char* source, unsigned char* dest, int length)
  * Filename must be a fully defined filename including the path and extension
  *
  ***************************************************************************/
-int rolo_load(char* filename)
+int rolo_load(const char* filename)
 {
     int fd;
     unsigned long length;
diff --git a/firmware/thread.c b/firmware/thread.c
index 7490833863..df90c7ac2f 100644
--- a/firmware/thread.c
+++ b/firmware/thread.c
@@ -71,7 +71,7 @@ static inline void store_context(void* addr)
  * Load non-volatile context.
  *---------------------------------------------------------------------------
  */
-static inline void load_context(void* addr)
+static inline void load_context(const void* addr)
 {
     asm volatile ("mov.l @%0+,r8\n\t"
                   "mov.l @%0+,r9\n\t"
diff --git a/uisimulator/win32/kernel.c b/uisimulator/win32/kernel.c
index 77ae6bffb2..b7c4af1eb1 100644
--- a/uisimulator/win32/kernel.c
+++ b/uisimulator/win32/kernel.c
@@ -94,7 +94,7 @@ void queue_post(struct event_queue *q, int id, void *data)
     set_irq_level(oldlevel);
 }
 
-bool queue_empty(struct event_queue* q)
+bool queue_empty(const struct event_queue* q)
 {
     return ( q->read == q->write );
 }