diff --git a/libraries/AP_HAL/utility/RingBuffer.cpp b/libraries/AP_HAL/utility/RingBuffer.cpp
index c1350b1655..34df541703 100644
--- a/libraries/AP_HAL/utility/RingBuffer.cpp
+++ b/libraries/AP_HAL/utility/RingBuffer.cpp
@@ -62,6 +62,7 @@ uint32_t ByteBuffer::write(const uint8_t *data, uint32_t len)
         ret += vec[i].len;
     }
 
+    commit(ret);
     return ret;
 }
 
@@ -142,36 +143,45 @@ uint32_t ByteBuffer::peekbytes(uint8_t *data, uint32_t len)
     return ret;
 }
 
-int ByteBuffer::reserve(ByteBuffer::IoVec iovec[2], uint32_t len)
+uint8_t ByteBuffer::reserve(ByteBuffer::IoVec iovec[2], uint32_t len)
 {
-    if (len > space()) {
-        len = space();
+    uint32_t n = space();
+
+    if (len > n) {
+        len = n;
     }
+
     if (!len) {
         return 0;
     }
 
     iovec[0].data = &buf[tail];
-    if (tail+len <= size) {
+
+    n = size - tail;
+    if (len <= n) {
         iovec[0].len = len;
-    } else {
-        auto n = size - tail;
-        if (n > len) {
-            n = len;
-        }
+        return 1;
+    }
 
-        iovec[0].len = n;
+    iovec[0].len = n;
 
-        tail = (tail + n) % size;
-        n = len - n;
-        if (n > 0) {
-            iovec[1].data = &buf[tail];
-            iovec[1].len = n;
-            return 2;
-        }
+    iovec[1].data = buf;
+    iovec[1].len = len - n;
+
+    return 2;
+}
+
+/*
+ * Advance the writer pointer by 'len'
+ */
+bool ByteBuffer::commit(uint32_t len)
+{
+    if (len > space()) {
+        return false; //Someone broke the agreement
     }
 
-    return 1;
+    tail = (tail + len) % size;
+    return true;
 }
 
 uint32_t ByteBuffer::read(uint8_t *data, uint32_t len)
diff --git a/libraries/AP_HAL/utility/RingBuffer.h b/libraries/AP_HAL/utility/RingBuffer.h
index 9db1e561d0..e021eb7f8e 100644
--- a/libraries/AP_HAL/utility/RingBuffer.h
+++ b/libraries/AP_HAL/utility/RingBuffer.h
@@ -86,8 +86,17 @@ public:
     // ring buffer (if wraparound is happening), or just one contiguous
     // part. Returns the number of `vec` elements filled out. Can be used
     // with system calls such as `readv()`.
-    int reserve(IoVec vec[2], uint32_t len);
-    
+    //
+    // After a call to 'reserve()', 'write()' should never be called
+    // until 'commit()' is called!
+    uint8_t reserve(IoVec vec[2], uint32_t len);
+
+    /*
+     * "Releases" the memory previously reserved by 'reserve()' to be read.
+     * Committer must inform how many bytes were actually written in 'len'.
+     */
+    bool commit(uint32_t len);
+
 private:
     uint8_t *buf = nullptr;
     uint32_t size = 0;