diff --git a/src/lib/support/Span.h b/src/lib/support/Span.h
index bd1e7cdd72219d..b6c5213bf5fe06 100644
--- a/src/lib/support/Span.h
+++ b/src/lib/support/Span.h
@@ -20,6 +20,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <string.h>
+#include <type_traits>
 
 #include <support/CodeUtils.h>
 
@@ -44,7 +45,10 @@ class Span
     constexpr pointer data() const { return mDataBuf; }
     size_t size() const { return mDataLen; }
     bool empty() const { return size() == 0; }
-    bool data_equal(const Span & other) const
+
+    // Allow data_equal for spans that are over the same type up to const-ness.
+    template <class U, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
+    bool data_equal(const Span<U> & other) const
     {
         return (size() == other.size()) && (empty() || (memcmp(data(), other.data(), size() * sizeof(T)) == 0));
     }
@@ -56,6 +60,20 @@ class Span
         return Span(mDataBuf + offset, length);
     }
 
+    // Allow converting a span with non-const T into a span with const T.
+    template <class U = T>
+    operator typename std::enable_if_t<!std::is_const<U>::value, Span<const T>>() const
+    {
+        return Span<const T>(data(), size());
+    }
+
+    // Allow reducing the size of a span.
+    void reduce_size(size_t new_size)
+    {
+        VerifyOrDie(new_size <= size());
+        mDataLen = new_size;
+    }
+
 private:
     pointer mDataBuf;
     size_t mDataLen;
@@ -73,12 +91,22 @@ class FixedSpan
     constexpr pointer data() const { return mDataBuf; }
     size_t size() const { return N; }
     bool empty() const { return data() == nullptr; }
-    bool data_equal(const FixedSpan & other) const
+
+    // Allow data_equal for spans that are over the same type up to const-ness.
+    template <class U, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
+    bool data_equal(const FixedSpan<U, N> & other) const
     {
         return (empty() && other.empty()) ||
             (!empty() && !other.empty() && (memcmp(data(), other.data(), size() * sizeof(T)) == 0));
     }
 
+    // Allow converting a span with non-const T into a span with const T.
+    template <class U = T>
+    operator typename std::enable_if_t<!std::is_const<U>::value, FixedSpan<const T, N>>() const
+    {
+        return FixedSpan<const T, N>(data());
+    }
+
 private:
     pointer mDataBuf;
 };
diff --git a/src/lib/support/tests/TestSpan.cpp b/src/lib/support/tests/TestSpan.cpp
index 5546df79b45719..83566db22bdaac 100644
--- a/src/lib/support/tests/TestSpan.cpp
+++ b/src/lib/support/tests/TestSpan.cpp
@@ -70,6 +70,74 @@ static void TestByteSpan(nlTestSuite * inSuite, void * inContext)
     NL_TEST_ASSERT(inSuite, !s5.data_equal(s4));
     NL_TEST_ASSERT(inSuite, s5.data_equal(s0));
     NL_TEST_ASSERT(inSuite, s0.data_equal(s5));
+
+    ByteSpan s6(arr2);
+    s6.reduce_size(2);
+    NL_TEST_ASSERT(inSuite, s6.size() == 2);
+    ByteSpan s7(arr2, 2);
+    NL_TEST_ASSERT(inSuite, s6.data_equal(s7));
+    NL_TEST_ASSERT(inSuite, s7.data_equal(s6));
+}
+
+static void TestMutableByteSpan(nlTestSuite * inSuite, void * inContext)
+{
+    uint8_t arr[] = { 1, 2, 3 };
+
+    MutableByteSpan s0 = MutableByteSpan();
+    NL_TEST_ASSERT(inSuite, s0.data() == nullptr);
+    NL_TEST_ASSERT(inSuite, s0.size() == 0);
+    NL_TEST_ASSERT(inSuite, s0.empty());
+    NL_TEST_ASSERT(inSuite, s0.data_equal(s0));
+
+    MutableByteSpan s1(arr, 2);
+    NL_TEST_ASSERT(inSuite, s1.data() == arr);
+    NL_TEST_ASSERT(inSuite, s1.size() == 2);
+    NL_TEST_ASSERT(inSuite, !s1.empty());
+    NL_TEST_ASSERT(inSuite, s1.data_equal(s1));
+    NL_TEST_ASSERT(inSuite, !s1.data_equal(s0));
+
+    MutableByteSpan s2(arr);
+    NL_TEST_ASSERT(inSuite, s2.data() == arr);
+    NL_TEST_ASSERT(inSuite, s2.size() == 3);
+    NL_TEST_ASSERT(inSuite, s2.data()[2] == 3);
+    NL_TEST_ASSERT(inSuite, !s2.empty());
+    NL_TEST_ASSERT(inSuite, s2.data_equal(s2));
+    NL_TEST_ASSERT(inSuite, !s2.data_equal(s1));
+
+    MutableByteSpan s3 = s2;
+    NL_TEST_ASSERT(inSuite, s3.data() == arr);
+    NL_TEST_ASSERT(inSuite, s3.size() == 3);
+    NL_TEST_ASSERT(inSuite, s3.data()[2] == 3);
+    NL_TEST_ASSERT(inSuite, !s3.empty());
+    NL_TEST_ASSERT(inSuite, s3.data_equal(s2));
+
+    uint8_t arr2[] = { 3, 2, 1 };
+    MutableByteSpan s4(arr2);
+    NL_TEST_ASSERT(inSuite, !s4.data_equal(s2));
+
+    MutableByteSpan s5(arr2, 0);
+    NL_TEST_ASSERT(inSuite, s5.data() != nullptr);
+    NL_TEST_ASSERT(inSuite, !s5.data_equal(s4));
+    NL_TEST_ASSERT(inSuite, s5.data_equal(s0));
+    NL_TEST_ASSERT(inSuite, s0.data_equal(s5));
+
+    MutableByteSpan s6(arr2);
+    s6.reduce_size(2);
+    NL_TEST_ASSERT(inSuite, s6.size() == 2);
+    MutableByteSpan s7(arr2, 2);
+    NL_TEST_ASSERT(inSuite, s6.data_equal(s7));
+    NL_TEST_ASSERT(inSuite, s7.data_equal(s6));
+
+    uint8_t arr3[] = { 1, 2, 3 };
+    MutableByteSpan s8(arr3);
+    NL_TEST_ASSERT(inSuite, arr3[1] == 2);
+    s8.data()[1] = 3;
+    NL_TEST_ASSERT(inSuite, arr3[1] == 3);
+
+    // Not mutable span on purpose, to test conversion.
+    ByteSpan s9 = s8;
+    NL_TEST_ASSERT(inSuite, s9.data_equal(s8));
+    NL_TEST_ASSERT(inSuite, s8.data_equal(s9));
 }
 
 static void TestFixedByteSpan(nlTestSuite * inSuite, void * inContext)
@@ -111,7 +179,8 @@ static void TestFixedByteSpan(nlTestSuite * inSuite, void * inContext)
 /**
  *   Test Suite. It lists all the test functions.
  */
-static const nlTest sTests[] = { NL_TEST_DEF_FN(TestByteSpan), NL_TEST_DEF_FN(TestFixedByteSpan), NL_TEST_SENTINEL() };
+static const nlTest sTests[] = { NL_TEST_DEF_FN(TestByteSpan), NL_TEST_DEF_FN(TestMutableByteSpan),
+                                 NL_TEST_DEF_FN(TestFixedByteSpan), NL_TEST_SENTINEL() };
 
 int TestSpan(void)
 {