soft_register: Remove compiler warning, add unit test

3 files changed, 41 insertions, 5 deletions

diff --git a/host/include/uhd/utils/soft_register.hpp b/host/include/uhd/utils/soft_register.hpp
index ac6ad4b35..fea4c0791 100644
--- a/host/include/uhd/utils/soft_register.hpp
+++ b/host/include/uhd/utils/soft_register.hpp
@@ -85,14 +85,16 @@ namespace soft_reg_field {
 
     template<typename data_t>
     UHD_INLINE data_t mask(const soft_reg_field_t field) {
-        static const data_t ONE = static_cast<data_t>(1);
+        constexpr data_t ONE = static_cast<data_t>(1);
+        constexpr data_t ALL_ONES = ~static_cast<data_t>(0);
         //Behavior for the left shift operation is undefined in C++
         //if the shift amount is >= bitwidth of the datatype
         //So we treat that as a special case with a branch predicition hint
-        if (likely((sizeof(data_t)*8) != width(field)))
+        if (likely((sizeof(data_t)*8) != width(field))) {
             return ((ONE<<width(field))-ONE)<<shift(field);
-        else
-            return (0-ONE)<<shift(field);
+        } else {
+            return ALL_ONES<<shift(field);
+        }
     }
 }
 
diff --git a/host/tests/CMakeLists.txt b/host/tests/CMakeLists.txt
index 7d53b50c4..ba0484e86 100644
--- a/host/tests/CMakeLists.txt
+++ b/host/tests/CMakeLists.txt
@@ -1,4 +1,4 @@
-#
+
 # Copyright 2010-2015 Ettus Research LLC
 # Copyright 2018 Ettus Research, a National Instruments Company
 #
@@ -34,6 +34,7 @@ SET(test_sources
     ranges_test.cpp
     sid_t_test.cpp
     sensors_test.cpp
+    soft_reg_test.cpp
     sph_recv_test.cpp
     sph_send_test.cpp
     subdev_spec_test.cpp
diff --git a/host/tests/soft_reg_test.cpp b/host/tests/soft_reg_test.cpp
new file mode 100644
index 000000000..8e53c61ca
--- /dev/null
+++ b/host/tests/soft_reg_test.cpp
@@ -0,0 +1,33 @@
+//
+// Copyright 2018 Ettus Research, a National Instruments Company
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+
+#include <uhd/utils/soft_register.hpp>
+#include <boost/test/unit_test.hpp>
+
+using namespace uhd;
+
+BOOST_AUTO_TEST_CASE(test_soft_reg_field) {
+    UHD_DEFINE_SOFT_REG_FIELD(test_reg1, /* width */ 1, /* shift */ 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::width(test_reg1), 1);
+    BOOST_CHECK_EQUAL(soft_reg_field::shift(test_reg1), 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::mask<uint32_t>(test_reg1),  1<<0);
+
+    UHD_DEFINE_SOFT_REG_FIELD(test_reg2, /* width */ 5, /* shift */ 4);
+    BOOST_CHECK_EQUAL(soft_reg_field::width(test_reg2), 5);
+    BOOST_CHECK_EQUAL(soft_reg_field::shift(test_reg2), 4);
+    BOOST_CHECK_EQUAL(soft_reg_field::mask<uint32_t>(test_reg2),  0x1F<<4);
+
+    UHD_DEFINE_SOFT_REG_FIELD(test_reg3, /* width */ 9, /* shift */ 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::width(test_reg3), 9);
+    BOOST_CHECK_EQUAL(soft_reg_field::shift(test_reg3), 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::mask<uint8_t>(test_reg3),  0xFF);
+
+    // This one is platform dependent:
+    UHD_DEFINE_SOFT_REG_FIELD(test_reg4, /* width */ 33, /* shift */ 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::width(test_reg4), 33);
+    BOOST_CHECK_EQUAL(soft_reg_field::shift(test_reg4), 0);
+    BOOST_CHECK_EQUAL(soft_reg_field::mask<size_t>(test_reg4), ~size_t(0) & 0x1FFFFFFFF);
+}