iio: Add basic unit test for iio_format_value()

The IIO core provides a function to do formatting of fixedpoint numbers.

In the past there have been some issues with the implementation of the
function where for example negative numbers were not handled correctly.

Introduce a basic unit test based on kunit that tests the function and
ensures that the generated output matches the expected output.

This gives us some confidence that future modifications to the function
implementation will not break ABI compatibility.

To run the unit tests follow the kunit documentation and add

  CONFIG_IIO=y
  CONFIG_IIO_TEST_FORMAT=y

to the .kunitconfig and run

  > ./tools/testing/kunit/kunit.py run
  Configuring KUnit Kernel ...
  Building KUnit Kernel ...
  Starting KUnit Kernel ...
  ============================================================
  ======== [PASSED] iio-format ========
  [PASSED] iio_test_iio_format_value_integer
  [PASSED] iio_test_iio_format_value_fixedpoint
  [PASSED] iio_test_iio_format_value_fractional
  [PASSED] iio_test_iio_format_value_fractional_log2
  [PASSED] iio_test_iio_format_value_multiple
  ============================================================
  Testing complete. 21 tests run. 0 failed. 0 crashed.
  Elapsed time: 8.242s total, 0.001s configuring, 3.865s building, 0.000s running
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20201215191743.2725-3-lars@metafoo.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/Kconfig

@@ -85,6 +85,7 @@ source "drivers/iio/light/Kconfig"
 source "drivers/iio/magnetometer/Kconfig"
 source "drivers/iio/multiplexer/Kconfig"
 source "drivers/iio/orientation/Kconfig"
+source "drivers/iio/test/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
 endif #IIO_TRIGGER

drivers/iio/Makefile

@@ -38,4 +38,5 @@ obj-y += pressure/
 obj-y += proximity/
 obj-y += resolver/
 obj-y += temperature/
+obj-y += test/
 obj-y += trigger/

drivers/iio/test/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Industrial I/O subsystem unit tests configuration
+#
+
+# Keep in alphabetical order
+config IIO_TEST_FORMAT
+        bool "Test IIO formatting functions"
+        depends on KUNIT=y

drivers/iio/test/Makefile

+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the industrial I/O unit tests.
+#
+
+# Keep in alphabetical order
+obj-$(CONFIG_IIO_TEST_FORMAT) += iio-test-format.o

drivers/iio/test/iio-test-format.c

+// SPDX-License-Identifier: GPL-2.0-only
+/* Unit tests for IIO formatting functions
+ *
+ * Copyright (c) 2020 Lars-Peter Clausen <lars@metafoo.de>
+ */
+
+#include <kunit/test.h>
+#include <linux/iio/iio.h>
+
+#define IIO_TEST_FORMAT_EXPECT_EQ(_test, _buf, _ret, _val) do { \
+		KUNIT_EXPECT_EQ(_test, (int)strlen(_buf), _ret); \
+		KUNIT_EXPECT_STREQ(_test, (_buf), (_val)); \
+	} while (0)
+
+static void iio_test_iio_format_value_integer(struct kunit *test)
+{
+	char *buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	int val;
+	int ret;
+
+	val = 42;
+	ret = iio_format_value(buf, IIO_VAL_INT, 1, &val);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "42\n");
+
+	val = -23;
+	ret = iio_format_value(buf, IIO_VAL_INT, 1, &val);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-23\n");
+
+	val = 0;
+	ret = iio_format_value(buf, IIO_VAL_INT, 1, &val);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0\n");
+
+	val = INT_MAX;
+	ret = iio_format_value(buf, IIO_VAL_INT, 1, &val);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "2147483647\n");
+
+	val = INT_MIN;
+	ret = iio_format_value(buf, IIO_VAL_INT, 1, &val);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-2147483648\n");
+}
+
+static void iio_test_iio_format_value_fixedpoint(struct kunit *test)
+{
+	char *buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	int values[2];
+	int ret;
+
+	/* positive >= 1 */
+	values[0] = 1;
+	values[1] = 10;
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000010\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000010 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000000010\n");
+
+	/* positive < 1 */
+	values[0] = 0;
+	values[1] = 12;
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000012\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000012 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000000012\n");
+
+	/* negative <= -1 */
+	values[0] = -1;
+	values[1] = 10;
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.000010\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.000010 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.000000010\n");
+
+	/* negative > -1 */
+	values[0] = 0;
+	values[1] = -123;
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000123\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000123 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000000123\n");
+}
+
+static void iio_test_iio_format_value_fractional(struct kunit *test)
+{
+	char *buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	int values[2];
+	int ret;
+
+	/* positive < 1 */
+	values[0] = 1;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.100000000\n");
+
+	/* positive >= 1 */
+	values[0] = 100;
+	values[1] = 3;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "33.333333333\n");
+
+	/* negative > -1 */
+	values[0] = -1;
+	values[1] = 1000000000;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000000001\n");
+
+	/* negative <= -1 */
+	values[0] = -200;
+	values[1] = 3;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-66.666666666\n");
+
+	/* Zero */
+	values[0] = 0;
+	values[1] = -10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000000000\n");
+}
+
+static void iio_test_iio_format_value_fractional_log2(struct kunit *test)
+{
+	char *buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	int values[2];
+	int ret;
+
+	/* positive < 1 */
+	values[0] = 123;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.120117187\n");
+
+	/* positive >= 1 */
+	values[0] = 1234567;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1205.631835937\n");
+
+	/* negative > -1 */
+	values[0] = -123;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.120117187\n");
+
+	/* negative <= -1 */
+	values[0] = -1234567;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1205.631835937\n");
+
+	/* Zero */
+	values[0] = 0;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, 2, values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000000000\n");
+}
+
+static void iio_test_iio_format_value_multiple(struct kunit *test)
+{
+	char *buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	int values[] = {1, -2, 3, -4, 5};
+	int ret;
+
+	ret = iio_format_value(buf, IIO_VAL_INT_MULTIPLE,
+			       ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1 -2 3 -4 5 \n");
+}
+
+static struct kunit_case iio_format_test_cases[] = {
+		KUNIT_CASE(iio_test_iio_format_value_integer),
+		KUNIT_CASE(iio_test_iio_format_value_fixedpoint),
+		KUNIT_CASE(iio_test_iio_format_value_fractional),
+		KUNIT_CASE(iio_test_iio_format_value_fractional_log2),
+		KUNIT_CASE(iio_test_iio_format_value_multiple),
+		{}
+};
+
+static struct kunit_suite iio_format_test_suite = {
+	.name = "iio-format",
+	.test_cases = iio_format_test_cases,
+};
+kunit_test_suite(iio_format_test_suite);