add const where possible (for message parsing)

firmware/messages.c

@@ -308,7 +308,7 @@ void msg_process(char type, uint16_t msg_id, const pb_field_t *fields, uint8_t *
 	}
 }
 
-void msg_read_common(char type, uint8_t *buf, int len)
+void msg_read_common(char type, const uint8_t *buf, int len)
 {
 	static char read_state = READSTATE_IDLE;
 	static uint8_t msg_in[MSG_IN_SIZE];
@@ -357,7 +357,7 @@ void msg_read_common(char type, uint8_t *buf, int len)
 	}
 }
 
-uint8_t *msg_out_data(void)
+const uint8_t *msg_out_data(void)
 {
 	if (msg_out_start == msg_out_end) return 0;
 	uint8_t *data = msg_out + (msg_out_start * 64);
@@ -368,7 +368,7 @@ uint8_t *msg_out_data(void)
 
 #if DEBUG_LINK
 
-uint8_t *msg_debug_out_data(void)
+const uint8_t *msg_debug_out_data(void)
 {
 	if (msg_debug_out_start == msg_debug_out_end) return 0;
 	uint8_t *data = msg_debug_out + (msg_debug_out_start * 64);
@@ -382,7 +382,7 @@ uint8_t *msg_debug_out_data(void)
 uint8_t msg_tiny[64];
 uint16_t msg_tiny_id = 0xFFFF;
 
-void msg_read_tiny(uint8_t *buf, int len)
+void msg_read_tiny(const uint8_t *buf, int len)
 {
 	if (len != 64) return;
 	if (buf[0] != '?' || buf[1] != '#' || buf[2] != '#') {

firmware/messages.h

@@ -30,7 +30,7 @@
 
 #define msg_read(buf, len) msg_read_common('n', (buf), (len))
 #define msg_write(id, ptr) msg_write_common('n', (id), (ptr))
-uint8_t *msg_out_data(void);
+const uint8_t *msg_out_data(void);
 
 #if DEBUG_LINK
 
@@ -38,15 +38,15 @@ uint8_t *msg_out_data(void);
 
 #define msg_debug_read(buf, len) msg_read_common('d', (buf), (len))
 #define msg_debug_write(id, ptr) msg_write_common('d', (id), (ptr))
-uint8_t *msg_debug_out_data(void);
+const uint8_t *msg_debug_out_data(void);
 
 #endif
 
-void msg_read_common(char type, uint8_t *buf, int len);
+void msg_read_common(char type, const uint8_t *buf, int len);
 bool msg_write_common(char type, uint16_t msg_id, const void *msg_ptr);
 
-void msg_read_tiny(uint8_t *buf, int len);
-void msg_debug_read_tiny(uint8_t *buf, int len);
+void msg_read_tiny(const uint8_t *buf, int len);
+void msg_debug_read_tiny(const uint8_t *buf, int len);
 extern uint8_t msg_tiny[64];
 extern uint16_t msg_tiny_id;
 

firmware/protob/pb_decode.c

@@ -151,7 +151,7 @@ static bool checkreturn pb_readbyte(pb_istream_t *stream, uint8_t *buf)
     return true;    
 }
 
-pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
+pb_istream_t pb_istream_from_buffer(const uint8_t *buf, size_t bufsize)
 {
     pb_istream_t stream;
 #ifdef PB_BUFFER_ONLY

firmware/protob/pb_decode.h

@@ -37,7 +37,7 @@ struct _pb_istream_t
     bool (*callback)(pb_istream_t *stream, uint8_t *buf, size_t count);
 #endif
 
-    void *state; /* Free field for use by callback implementation */
+    const void *state; /* Free field for use by callback implementation */
     size_t bytes_left;
     
 #ifndef PB_NO_ERRMSG
@@ -103,7 +103,7 @@ void pb_release(const pb_field_t fields[], void *dest_struct);
  * Alternatively, you can use a custom stream that reads directly from e.g.
  * a file or a network socket.
  */
-pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize);
+pb_istream_t pb_istream_from_buffer(const uint8_t *buf, size_t bufsize);
 
 /* Function to read from a pb_istream_t. You can use this if you need to
  * read some custom header data, or to read data in field callbacks.

firmware/usb.c

@@ -391,7 +391,7 @@ void usbInit(void)
 
 void usbPoll(void)
 {
-	static uint8_t *data;
+	static const uint8_t *data;
 	// poll read buffer
 	usbd_poll(usbd_dev);
 	// write pending data