x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

6 files changed, 1835 insertions, 0 deletions

diff --git a/drivers/iio/test/Kconfig b/drivers/iio/test/Kconfig
new file mode 100644
index 000000000..4fc17dd0d
--- /dev/null
+++ b/drivers/iio/test/Kconfig
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Industrial I/O subsystem unit tests configuration
+#
+
+# Keep in alphabetical order
+config IIO_GTS_KUNIT_TEST
+	tristate "Test IIO gain-time-scale helpers" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	select IIO_GTS_HELPER
+	default KUNIT_ALL_TESTS
+	help
+	  build unit tests for the IIO light sensor gain-time-scale helpers.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N. Keep in alphabetical order
+
+config IIO_RESCALE_KUNIT_TEST
+	tristate "Test IIO rescale conversion functions" if !KUNIT_ALL_TESTS
+	depends on KUNIT && IIO_RESCALE
+	default KUNIT_ALL_TESTS
+	help
+	  Build unit tests for the iio-rescale code.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+config IIO_FORMAT_KUNIT_TEST
+	tristate "Test IIO formatting functions" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  build unit tests for the IIO formatting functions.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
+config IIO_MULTIPLY_KUNIT_TEST
+	tristate "Test IIO multiply functions" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  build unit tests for the IIO multiply functions.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
diff --git a/drivers/iio/test/Makefile b/drivers/iio/test/Makefile
new file mode 100644
index 000000000..0c846bc21
--- /dev/null
+++ b/drivers/iio/test/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the industrial I/O unit tests.
+#
+
+# Keep in alphabetical order
+obj-$(CONFIG_IIO_RESCALE_KUNIT_TEST) += iio-test-rescale.o
+obj-$(CONFIG_IIO_FORMAT_KUNIT_TEST) += iio-test-format.o
+obj-$(CONFIG_IIO_GTS_KUNIT_TEST) += iio-test-gts.o
+obj-$(CONFIG_IIO_MULTIPLY_KUNIT_TEST) += iio-test-multiply.o
+CFLAGS_iio-test-format.o += $(DISABLE_STRUCTLEAK_PLUGIN)
diff --git a/drivers/iio/test/iio-test-format.c b/drivers/iio/test/iio-test-format.c
new file mode 100644
index 000000000..e5d0a2ac4
--- /dev/null
+++ b/drivers/iio/test/iio-test-format.c
@@ -0,0 +1,324 @@
+// 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, strlen(_buf), _ret); \
+		KUNIT_EXPECT_STREQ(_test, (_buf), (_val)); \
+	} while (0)
+
+static void iio_test_iio_format_value_integer(struct kunit *test)
+{
+	char *buf;
+	int val;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	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)
+{
+	int values[2];
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	/* positive >= 1 */
+	values[0] = 1;
+	values[1] = 10;
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000010\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000010 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000012\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000012 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.000010\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.000010 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000123\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_MICRO_DB, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000123 dB\n");
+
+	ret = iio_format_value(buf, IIO_VAL_INT_PLUS_NANO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.000000123\n");
+}
+
+static void iio_test_iio_format_value_fractional(struct kunit *test)
+{
+	int values[2];
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	/* positive < 1 */
+	values[0] = 1;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000000000\n");
+}
+
+static void iio_test_iio_format_value_fractional_log2(struct kunit *test)
+{
+	int values[2];
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	/* positive < 1 */
+	values[0] = 123;
+	values[1] = 10;
+	ret = iio_format_value(buf, IIO_VAL_FRACTIONAL_LOG2, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), 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, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000000000\n");
+}
+
+static void iio_test_iio_format_value_multiple(struct kunit *test)
+{
+	int values[] = {1, -2, 3, -4, 5};
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	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 void iio_test_iio_format_value_integer_64(struct kunit *test)
+{
+	int values[2];
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	iio_val_s64_decompose(24, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "24\n");
+
+	iio_val_s64_decompose(-24, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-24\n");
+
+	iio_val_s64_decompose(0, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0\n");
+
+	iio_val_s64_decompose(UINT_MAX, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "4294967295\n");
+
+	iio_val_s64_decompose(-((s64)UINT_MAX), &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-4294967295\n");
+
+	iio_val_s64_decompose(LLONG_MAX, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "9223372036854775807\n");
+
+	iio_val_s64_decompose(LLONG_MIN, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_INT_64, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-9223372036854775808\n");
+}
+
+static void iio_test_iio_format_value_decimal_64(struct kunit *test)
+{
+	int values[2];
+	char *buf;
+	int ret;
+
+	buf = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	/* DECIMAL64_MILLI: positive >= 1, value 1.234 */
+	iio_val_s64_decompose(1234, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MILLI, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.234\n");
+
+	/* DECIMAL64_MICRO: positive >= 1, value 3.141592 */
+	iio_val_s64_decompose(3141592, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MICRO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "3.141592\n");
+
+	/* DECIMAL64_MILLI: positive < 1, value 0.042 */
+	iio_val_s64_decompose(42, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MILLI, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.042\n");
+
+	/* DECIMAL64_MILLI: negative <= -1, value -1.234 */
+	iio_val_s64_decompose(-1234, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MILLI, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-1.234\n");
+
+	/* DECIMAL64_MILLI: negative > -1, value -0.123 */
+	iio_val_s64_decompose(-123, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MILLI, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-0.123\n");
+
+	/* DECIMAL64_MILLI: zero */
+	iio_val_s64_decompose(0, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MILLI, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "0.000\n");
+
+	/* DECIMAL64_NANO: value 1.000000001 */
+	iio_val_s64_decompose(1000000001, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_NANO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "1.000000001\n");
+
+	/* DECIMAL64_MICRO: large value using upper 32 bits */
+	iio_val_s64_decompose(5000000000000042LL, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MICRO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "5000000000.000042\n");
+
+	/* limits */
+	iio_val_s64_decompose(LLONG_MAX, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_PICO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "9223372.036854775807\n");
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_NANO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "9223372036.854775807\n");
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MICRO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "9223372036854.775807\n");
+
+	iio_val_s64_decompose(LLONG_MIN, &values[0], &values[1]);
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_PICO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-9223372.036854775808\n");
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_NANO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-9223372036.854775808\n");
+	ret = iio_format_value(buf, IIO_VAL_DECIMAL64_MICRO, ARRAY_SIZE(values), values);
+	IIO_TEST_FORMAT_EXPECT_EQ(test, buf, ret, "-9223372036854.775808\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),
+		KUNIT_CASE(iio_test_iio_format_value_integer_64),
+		KUNIT_CASE(iio_test_iio_format_value_decimal_64),
+		{ }
+};
+
+static struct kunit_suite iio_format_test_suite = {
+	.name = "iio-format",
+	.test_cases = iio_format_test_cases,
+};
+kunit_test_suite(iio_format_test_suite);
+
+MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
+MODULE_DESCRIPTION("Test IIO formatting functions");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/iio/test/iio-test-gts.c b/drivers/iio/test/iio-test-gts.c
new file mode 100644
index 000000000..6ffff85ba
--- /dev/null
+++ b/drivers/iio/test/iio-test-gts.c
@@ -0,0 +1,515 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unit tests for IIO light sensor gain-time-scale helpers
+ *
+ * Copyright (c) 2023 Matti Vaittinen <mazziesaccount@gmail.com>
+ */
+
+#include <kunit/device.h>
+#include <kunit/test.h>
+#include <linux/device.h>
+#include <linux/iio/iio-gts-helper.h>
+#include <linux/iio/types.h>
+
+/*
+ * Please, read the "rant" from the top of the lib/test_linear_ranges.c if
+ * you see a line of helper code which is not being tested.
+ *
+ * Then, please look at the line which is not being tested. Is this line
+ * somehow unusually complex? If answer is "no", then chances are that the
+ * "development inertia" caused by adding a test exceeds the benefits.
+ *
+ * If yes, then adding a test is probably a good idea but please stop for a
+ * moment and consider the effort of changing all the tests when code gets
+ * refactored. Eventually it needs to be.
+ */
+
+#define TEST_TSEL_50		1
+#define TEST_TSEL_X_MIN		TEST_TSEL_50
+#define TEST_TSEL_100		0
+#define TEST_TSEL_200		2
+#define TEST_TSEL_400		4
+#define TEST_TSEL_X_MAX		TEST_TSEL_400
+
+#define TEST_GSEL_1		0x00
+#define TEST_GSEL_X_MIN		TEST_GSEL_1
+#define TEST_GSEL_4		0x08
+#define TEST_GSEL_16		0x0a
+#define TEST_GSEL_32		0x0b
+#define TEST_GSEL_64		0x0c
+#define TEST_GSEL_256		0x18
+#define TEST_GSEL_512		0x19
+#define TEST_GSEL_1024		0x1a
+#define TEST_GSEL_2048		0x1b
+#define TEST_GSEL_4096		0x1c
+#define TEST_GSEL_X_MAX		TEST_GSEL_4096
+
+#define TEST_SCALE_1X		64
+#define TEST_SCALE_MIN_X	TEST_SCALE_1X
+#define TEST_SCALE_2X		32
+#define TEST_SCALE_4X		16
+#define TEST_SCALE_8X		8
+#define TEST_SCALE_16X		4
+#define TEST_SCALE_32X		2
+#define TEST_SCALE_64X		1
+
+#define TEST_SCALE_NANO_128X	500000000
+#define TEST_SCALE_NANO_256X	250000000
+#define TEST_SCALE_NANO_512X	125000000
+#define TEST_SCALE_NANO_1024X	62500000
+#define TEST_SCALE_NANO_2048X	31250000
+#define TEST_SCALE_NANO_4096X	15625000
+#define TEST_SCALE_NANO_4096X2	7812500
+#define TEST_SCALE_NANO_4096X4	3906250
+#define TEST_SCALE_NANO_4096X8	1953125
+
+#define TEST_SCALE_NANO_MAX_X TEST_SCALE_NANO_4096X8
+
+/*
+ * Can't have this allocated from stack because the kunit clean-up will
+ * happen only after the test function has already gone
+ */
+static struct iio_gts gts;
+
+/* Keep the gain and time tables unsorted to test the sorting */
+static const struct iio_gain_sel_pair gts_test_gains[] = {
+	GAIN_SCALE_GAIN(1, TEST_GSEL_1),
+	GAIN_SCALE_GAIN(4, TEST_GSEL_4),
+	GAIN_SCALE_GAIN(16, TEST_GSEL_16),
+	GAIN_SCALE_GAIN(32, TEST_GSEL_32),
+	GAIN_SCALE_GAIN(64, TEST_GSEL_64),
+	GAIN_SCALE_GAIN(256, TEST_GSEL_256),
+	GAIN_SCALE_GAIN(512, TEST_GSEL_512),
+	GAIN_SCALE_GAIN(1024, TEST_GSEL_1024),
+	GAIN_SCALE_GAIN(4096, TEST_GSEL_4096),
+	GAIN_SCALE_GAIN(2048, TEST_GSEL_2048),
+#define HWGAIN_MAX 4096
+};
+
+static const struct iio_itime_sel_mul gts_test_itimes[] = {
+	GAIN_SCALE_ITIME_US(100 * 1000, TEST_TSEL_100, 2),
+	GAIN_SCALE_ITIME_US(400 * 1000, TEST_TSEL_400, 8),
+	GAIN_SCALE_ITIME_US(400 * 1000, TEST_TSEL_400, 8),
+	GAIN_SCALE_ITIME_US(50 * 1000, TEST_TSEL_50, 1),
+	GAIN_SCALE_ITIME_US(200 * 1000, TEST_TSEL_200, 4),
+#define TIMEGAIN_MAX 8
+};
+#define TOTAL_GAIN_MAX	(HWGAIN_MAX * TIMEGAIN_MAX)
+#define IIO_GTS_TEST_DEV "iio-gts-test-dev"
+
+static struct device *__test_init_iio_gain_scale(struct kunit *test,
+		struct iio_gts *gts, const struct iio_gain_sel_pair *g_table,
+		int num_g, const struct iio_itime_sel_mul *i_table, int num_i)
+{
+	struct device *dev;
+	int ret;
+
+	dev = kunit_device_register(test, IIO_GTS_TEST_DEV);
+
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, dev);
+	if (IS_ERR_OR_NULL(dev))
+		return NULL;
+
+	ret = devm_iio_init_iio_gts(dev, TEST_SCALE_1X, 0, g_table, num_g,
+				    i_table, num_i, gts);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	if (ret)
+		return NULL;
+
+	return dev;
+}
+
+#define test_init_iio_gain_scale(test, gts)	\
+	__test_init_iio_gain_scale(test, gts, gts_test_gains, \
+				   ARRAY_SIZE(gts_test_gains), gts_test_itimes, \
+				   ARRAY_SIZE(gts_test_itimes))
+
+static void test_init_iio_gts_invalid(struct kunit *test)
+{
+	struct device *dev;
+	int ret;
+	const struct iio_itime_sel_mul itimes_neg[] = {
+		GAIN_SCALE_ITIME_US(-10, TEST_TSEL_400, 8),
+		GAIN_SCALE_ITIME_US(200 * 1000, TEST_TSEL_200, 4),
+	};
+	const struct iio_gain_sel_pair gains_neg[] = {
+		GAIN_SCALE_GAIN(1, TEST_GSEL_1),
+		GAIN_SCALE_GAIN(2, TEST_GSEL_4),
+		GAIN_SCALE_GAIN(-2, TEST_GSEL_16),
+	};
+	/* 55555 * 38656 = 2147534080 => overflows 32bit int */
+	const struct iio_itime_sel_mul itimes_overflow[] = {
+		GAIN_SCALE_ITIME_US(400 * 1000, TEST_TSEL_400, 55555),
+		GAIN_SCALE_ITIME_US(200 * 1000, TEST_TSEL_200, 4),
+	};
+	const struct iio_gain_sel_pair gains_overflow[] = {
+		GAIN_SCALE_GAIN(1, TEST_GSEL_1),
+		GAIN_SCALE_GAIN(2, TEST_GSEL_4),
+		GAIN_SCALE_GAIN(38656, TEST_GSEL_16),
+	};
+
+	dev = kunit_device_register(test, IIO_GTS_TEST_DEV);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, dev);
+	if (!dev)
+		return;
+
+	/* Ok gains, negative time */
+	ret = devm_iio_init_iio_gts(dev, TEST_SCALE_1X, 0, gts_test_gains,
+				    ARRAY_SIZE(gts_test_gains), itimes_neg,
+				    ARRAY_SIZE(itimes_neg), &gts);
+	KUNIT_EXPECT_EQ(test, -EINVAL, ret);
+
+	/* Ok times, negative gain */
+	ret = devm_iio_init_iio_gts(dev, TEST_SCALE_1X, 0, gains_neg,
+				    ARRAY_SIZE(gains_neg), gts_test_itimes,
+				    ARRAY_SIZE(gts_test_itimes), &gts);
+	KUNIT_EXPECT_EQ(test, -EINVAL, ret);
+
+	/* gain * time overflow int */
+	ret = devm_iio_init_iio_gts(dev, TEST_SCALE_1X, 0, gains_overflow,
+				    ARRAY_SIZE(gains_overflow), itimes_overflow,
+				    ARRAY_SIZE(itimes_overflow), &gts);
+	KUNIT_EXPECT_EQ(test, -EOVERFLOW, ret);
+}
+
+static void test_iio_gts_find_gain_for_scale_using_time(struct kunit *test)
+{
+	struct device *dev;
+	int ret, gain_sel;
+
+	dev = test_init_iio_gain_scale(test, &gts);
+	if (!dev)
+		return;
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_100,
+						TEST_SCALE_8X, 0, &gain_sel);
+	/*
+	 * Meas time 100 => gain by time 2x
+	 * TEST_SCALE_8X matches total gain 8x
+	 * => required HWGAIN 4x
+	 */
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_GSEL_4, gain_sel);
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_200, 0,
+						TEST_SCALE_NANO_256X, &gain_sel);
+	/*
+	 * Meas time 200 => gain by time 4x
+	 * TEST_SCALE_256X matches total gain 256x
+	 * => required HWGAIN 256/4 => 64x
+	 */
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_GSEL_64, gain_sel);
+
+	/* Min time, Min gain */
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_X_MIN,
+						TEST_SCALE_MIN_X, 0, &gain_sel);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_GSEL_1, gain_sel);
+
+	/* Max time, Max gain */
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_X_MAX,
+					0, TEST_SCALE_NANO_MAX_X, &gain_sel);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_GSEL_4096, gain_sel);
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_100, 0,
+						TEST_SCALE_NANO_256X, &gain_sel);
+	/*
+	 * Meas time 100 => gain by time 2x
+	 * TEST_SCALE_256X matches total gain 256x
+	 * => required HWGAIN 256/2 => 128x (not in gain-table - unsupported)
+	 */
+	KUNIT_EXPECT_NE(test, 0, ret);
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_200, 0,
+						TEST_SCALE_NANO_MAX_X, &gain_sel);
+	/* We can't reach the max gain with integration time smaller than MAX */
+	KUNIT_EXPECT_NE(test, 0, ret);
+
+	ret = iio_gts_find_gain_sel_for_scale_using_time(&gts, TEST_TSEL_50, 0,
+						TEST_SCALE_NANO_MAX_X, &gain_sel);
+	/* We can't reach the max gain with integration time smaller than MAX */
+	KUNIT_EXPECT_NE(test, 0, ret);
+}
+
+static void test_iio_gts_find_new_gain_sel_by_old_gain_time(struct kunit *test)
+{
+	struct device *dev;
+	int ret, old_gain, new_gain, old_time_sel, new_time_sel;
+
+	dev = test_init_iio_gain_scale(test, &gts);
+	if (!dev)
+		return;
+
+	old_gain = 32;
+	old_time_sel = TEST_TSEL_200;
+	new_time_sel = TEST_TSEL_400;
+
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	/*
+	 * Doubling the integration time doubles the total gain - so old
+	 * (hw)gain must be divided by two to compensate. => 32 / 2 => 16
+	 */
+	KUNIT_EXPECT_EQ(test, 16, new_gain);
+
+	old_gain = 4;
+	old_time_sel = TEST_TSEL_50;
+	new_time_sel = TEST_TSEL_200;
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	/*
+	 * gain by time 1x => 4x - (hw)gain 4x => 1x
+	 */
+	KUNIT_EXPECT_EQ(test, 1, new_gain);
+
+	old_gain = 512;
+	old_time_sel = TEST_TSEL_400;
+	new_time_sel = TEST_TSEL_50;
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	/*
+	 * gain by time 8x => 1x - (hw)gain 512x => 4096x)
+	 */
+	KUNIT_EXPECT_EQ(test, 4096, new_gain);
+
+	/* Unsupported gain 2x */
+	old_gain = 4;
+	old_time_sel = TEST_TSEL_200;
+	new_time_sel = TEST_TSEL_400;
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_NE(test, 0, ret);
+
+	/* Too small gain */
+	old_gain = 4;
+	old_time_sel = TEST_TSEL_50;
+	new_time_sel = TEST_TSEL_400;
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_NE(test, 0, ret);
+
+	/* Too big gain */
+	old_gain = 1024;
+	old_time_sel = TEST_TSEL_400;
+	new_time_sel = TEST_TSEL_50;
+	ret = iio_gts_find_new_gain_sel_by_old_gain_time(&gts, old_gain,
+					old_time_sel, new_time_sel, &new_gain);
+	KUNIT_EXPECT_NE(test, 0, ret);
+
+}
+
+static void test_iio_find_closest_gain_low(struct kunit *test)
+{
+	struct device *dev;
+	bool in_range;
+	int ret;
+
+	const struct iio_gain_sel_pair gts_test_gains_gain_low[] = {
+		GAIN_SCALE_GAIN(4, TEST_GSEL_4),
+		GAIN_SCALE_GAIN(16, TEST_GSEL_16),
+		GAIN_SCALE_GAIN(32, TEST_GSEL_32),
+	};
+
+	dev = test_init_iio_gain_scale(test, &gts);
+	if (!dev)
+		return;
+
+	ret = iio_find_closest_gain_low(&gts, 2, &in_range);
+	KUNIT_EXPECT_EQ(test, 1, ret);
+	KUNIT_EXPECT_EQ(test, true, in_range);
+
+	ret = iio_find_closest_gain_low(&gts, 1, &in_range);
+	KUNIT_EXPECT_EQ(test, 1, ret);
+	KUNIT_EXPECT_EQ(test, true, in_range);
+
+	ret = iio_find_closest_gain_low(&gts, 4095, &in_range);
+	KUNIT_EXPECT_EQ(test, 2048, ret);
+	KUNIT_EXPECT_EQ(test, true, in_range);
+
+	ret = iio_find_closest_gain_low(&gts, 4097, &in_range);
+	KUNIT_EXPECT_EQ(test, 4096, ret);
+	KUNIT_EXPECT_EQ(test, false, in_range);
+
+	kunit_device_unregister(test, dev);
+
+	dev = __test_init_iio_gain_scale(test, &gts, gts_test_gains_gain_low,
+				ARRAY_SIZE(gts_test_gains_gain_low),
+				gts_test_itimes, ARRAY_SIZE(gts_test_itimes));
+	if (!dev)
+		return;
+
+	ret = iio_find_closest_gain_low(&gts, 3, &in_range);
+	KUNIT_EXPECT_EQ(test, -EINVAL, ret);
+	KUNIT_EXPECT_EQ(test, false, in_range);
+}
+
+static void test_iio_gts_total_gain_to_scale(struct kunit *test)
+{
+	struct device *dev;
+	int ret, scale_int, scale_nano;
+
+	dev = test_init_iio_gain_scale(test, &gts);
+	if (!dev)
+		return;
+
+	ret = iio_gts_total_gain_to_scale(&gts, 1, &scale_int, &scale_nano);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_SCALE_1X, scale_int);
+	KUNIT_EXPECT_EQ(test, 0, scale_nano);
+
+	ret = iio_gts_total_gain_to_scale(&gts, 1, &scale_int, &scale_nano);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, TEST_SCALE_1X, scale_int);
+	KUNIT_EXPECT_EQ(test, 0, scale_nano);
+
+	ret = iio_gts_total_gain_to_scale(&gts, 4096 * 8, &scale_int,
+					  &scale_nano);
+	KUNIT_EXPECT_EQ(test, 0, ret);
+	KUNIT_EXPECT_EQ(test, 0, scale_int);
+	KUNIT_EXPECT_EQ(test, TEST_SCALE_NANO_4096X8, scale_nano);
+}
+
+static void test_iio_gts_chk_times(struct kunit *test, const int *vals)
+{
+	static const int expected[] = {0, 50000, 0, 100000, 0, 200000, 0, 400000};
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(expected); i++)
+		KUNIT_EXPECT_EQ(test, expected[i], vals[i]);
+}
+
+static void test_iio_gts_chk_scales_all(struct kunit *test, struct iio_gts *gts,
+					const int *vals, int len)
+{
+	static const int gains[] = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512,
+				    1024, 2048, 4096, 4096 * 2, 4096 * 4,
+				    4096 * 8};
+	int expected[ARRAY_SIZE(gains) * 2];
+	int i, ret;
+	int exp_len = ARRAY_SIZE(gains) * 2;
+
+	KUNIT_EXPECT_EQ(test, exp_len, len);
+	if (len != exp_len)
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(gains); i++) {
+		ret = iio_gts_total_gain_to_scale(gts, gains[i],
+						  &expected[2 * i],
+						  &expected[2 * i + 1]);
+		KUNIT_EXPECT_EQ(test, 0, ret);
+		if (ret)
+			return;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(expected); i++)
+		KUNIT_EXPECT_EQ(test, expected[i], vals[i]);
+}
+
+static void test_iio_gts_chk_scales_t200(struct kunit *test, struct iio_gts *gts,
+					 const int *vals, int len)
+{
+	/* The gain caused by time 200 is 4x */
+	static const int gains[] = {
+		1 * 4,
+		4 * 4,
+		16 * 4,
+		32 * 4,
+		64 * 4,
+		256 * 4,
+		512 * 4,
+		1024 * 4,
+		2048 * 4,
+		4096 * 4
+	};
+	int expected[ARRAY_SIZE(gains) * 2];
+	int i, ret;
+
+	KUNIT_EXPECT_EQ(test, 2 * ARRAY_SIZE(gains), len);
+	if (len < 2 * ARRAY_SIZE(gains))
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(gains); i++) {
+		ret = iio_gts_total_gain_to_scale(gts, gains[i],
+						  &expected[2 * i],
+						  &expected[2 * i + 1]);
+		KUNIT_EXPECT_EQ(test, 0, ret);
+		if (ret)
+			return;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(expected); i++)
+		KUNIT_EXPECT_EQ(test, expected[i], vals[i]);
+}
+
+static void test_iio_gts_avail_test(struct kunit *test)
+{
+	struct device *dev;
+	int ret;
+	int type, len;
+	const int *vals;
+
+	dev = test_init_iio_gain_scale(test, &gts);
+	if (!dev)
+		return;
+
+	/* test table building for times and iio_gts_avail_times() */
+	ret = iio_gts_avail_times(&gts, &vals, &type, &len);
+	KUNIT_EXPECT_EQ(test, IIO_AVAIL_LIST, ret);
+	if (ret)
+		return;
+
+	KUNIT_EXPECT_EQ(test, IIO_VAL_INT_PLUS_MICRO, type);
+	KUNIT_EXPECT_EQ(test, 8, len);
+	if (len < 8)
+		return;
+
+	test_iio_gts_chk_times(test, vals);
+
+	/* Test table building for all scales and iio_gts_all_avail_scales() */
+	ret = iio_gts_all_avail_scales(&gts, &vals, &type, &len);
+	KUNIT_EXPECT_EQ(test, IIO_AVAIL_LIST, ret);
+	if (ret)
+		return;
+
+	KUNIT_EXPECT_EQ(test, IIO_VAL_INT_PLUS_NANO, type);
+
+	test_iio_gts_chk_scales_all(test, &gts, vals, len);
+
+	/*
+	 * Test table building for scales/time and
+	 * iio_gts_avail_scales_for_time()
+	 */
+	ret = iio_gts_avail_scales_for_time(&gts, 200000, &vals, &type, &len);
+	KUNIT_EXPECT_EQ(test, IIO_AVAIL_LIST, ret);
+	if (ret)
+		return;
+
+	KUNIT_EXPECT_EQ(test, IIO_VAL_INT_PLUS_NANO, type);
+	test_iio_gts_chk_scales_t200(test, &gts, vals, len);
+}
+
+static struct kunit_case iio_gts_test_cases[] = {
+	KUNIT_CASE(test_init_iio_gts_invalid),
+	KUNIT_CASE(test_iio_gts_find_gain_for_scale_using_time),
+	KUNIT_CASE(test_iio_gts_find_new_gain_sel_by_old_gain_time),
+	KUNIT_CASE(test_iio_find_closest_gain_low),
+	KUNIT_CASE(test_iio_gts_total_gain_to_scale),
+	KUNIT_CASE(test_iio_gts_avail_test),
+	{ }
+};
+
+static struct kunit_suite iio_gts_test_suite = {
+	.name = "iio-gain-time-scale",
+	.test_cases = iio_gts_test_cases,
+};
+
+kunit_test_suite(iio_gts_test_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>");
+MODULE_DESCRIPTION("Test IIO light sensor gain-time-scale helpers");
+MODULE_IMPORT_NS("IIO_GTS_HELPER");
diff --git a/drivers/iio/test/iio-test-multiply.c b/drivers/iio/test/iio-test-multiply.c
new file mode 100644
index 000000000..432e279ff
--- /dev/null
+++ b/drivers/iio/test/iio-test-multiply.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unit tests for IIO multiply functions
+ *
+ * Copyright (c) 2025 Hans de Goede <hans@hansg.org>
+ * Based on iio-test-format.c which is:
+ * Copyright (c) 2020 Lars-Peter Clausen <lars@metafoo.de>
+ */
+
+#include <kunit/test.h>
+#include <linux/iio/consumer.h>
+#include <linux/math64.h>
+#include <linux/types.h>
+
+static void __iio_test_iio_multiply_value_integer(struct kunit *test, s64 multiplier)
+{
+	int ret, result, val;
+
+	val = 42;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT, val, 0);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, multiplier * val);
+
+	val = -23;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT, val, 0);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, multiplier * val);
+
+	val = 0;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT, val, 0);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, multiplier * val);
+}
+
+static void iio_test_iio_multiply_value_integer(struct kunit *test)
+{
+	__iio_test_iio_multiply_value_integer(test, 20);
+	__iio_test_iio_multiply_value_integer(test, -20);
+}
+
+static void __iio_test_iio_multiply_value_fixedpoint(struct kunit *test, s64 multiplier)
+{
+	int ret, result, val, val2;
+
+	/* positive >= 1 (1.5) */
+	val = 1;
+	val2 = 500000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_MICRO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * 15, 10));
+
+	val = 1;
+	val2 = 500000000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_NANO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * 15, 10));
+
+	/* positive < 1 (0.5) */
+	val = 0;
+	val2 = 500000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_MICRO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * 5, 10));
+
+	val = 0;
+	val2 = 500000000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_NANO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * 5, 10));
+
+	/* negative <= -1 (-1.5) */
+	val = -1;
+	val2 = 500000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_MICRO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * -15, 10));
+
+	val = -1;
+	val2 = 500000000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_NANO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * -15, 10));
+
+	/* negative > -1 (-0.5) */
+	val = 0;
+	val2 = -500000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_MICRO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * -5, 10));
+
+	val = 0;
+	val2 = -500000000;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_INT_PLUS_NANO, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * -5, 10));
+}
+
+static void iio_test_iio_multiply_value_fixedpoint(struct kunit *test)
+{
+	__iio_test_iio_multiply_value_fixedpoint(test, 20);
+	__iio_test_iio_multiply_value_fixedpoint(test, -20);
+}
+
+static void __iio_test_iio_multiply_value_fractional(struct kunit *test, s64 multiplier)
+{
+	int ret, result, val, val2;
+
+	/* positive < 1 (1/10)*/
+	val = 1;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * val, val2));
+
+	/* positive >= 1 (100/3)*/
+	val = 100;
+	val2 = 3;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * val, val2));
+
+	/* negative > -1 (-1/10) */
+	val = -1;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * val, val2));
+
+	/* negative <= -1 (-200/3)*/
+	val = -200;
+	val2 = 3;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * val, val2));
+
+	/* Zero (0/-10) */
+	val = 0;
+	val2 = -10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, div_s64(multiplier * val, val2));
+}
+
+static void iio_test_iio_multiply_value_fractional(struct kunit *test)
+{
+	__iio_test_iio_multiply_value_fractional(test, 20);
+	__iio_test_iio_multiply_value_fractional(test, -20);
+}
+
+static void __iio_test_iio_multiply_value_fractional_log2(struct kunit *test, s64 multiplier)
+{
+	int ret, result, val, val2;
+
+	/* positive < 1 (123/1024) */
+	val = 123;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL_LOG2, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, (multiplier * val) >> val2);
+
+	/* positive >= 1 (1234567/1024) */
+	val = 1234567;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL_LOG2, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, (multiplier * val) >> val2);
+
+	/* negative > -1 (-123/1024) */
+	val = -123;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL_LOG2, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, (multiplier * val) >> val2);
+
+	/* negative <= -1 (-1234567/1024) */
+	val = -1234567;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL_LOG2, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, (multiplier * val) >> val2);
+
+	/* Zero (0/1024) */
+	val = 0;
+	val2 = 10;
+	ret = iio_multiply_value(&result, multiplier, IIO_VAL_FRACTIONAL_LOG2, val, val2);
+	KUNIT_EXPECT_EQ(test, ret, IIO_VAL_INT);
+	KUNIT_EXPECT_EQ(test, result, (multiplier * val) >> val2);
+}
+
+static void iio_test_iio_multiply_value_fractional_log2(struct kunit *test)
+{
+	__iio_test_iio_multiply_value_fractional_log2(test, 20);
+	__iio_test_iio_multiply_value_fractional_log2(test, -20);
+}
+
+static struct kunit_case iio_multiply_test_cases[] = {
+		KUNIT_CASE(iio_test_iio_multiply_value_integer),
+		KUNIT_CASE(iio_test_iio_multiply_value_fixedpoint),
+		KUNIT_CASE(iio_test_iio_multiply_value_fractional),
+		KUNIT_CASE(iio_test_iio_multiply_value_fractional_log2),
+		{ }
+};
+
+static struct kunit_suite iio_multiply_test_suite = {
+	.name = "iio-multiply",
+	.test_cases = iio_multiply_test_cases,
+};
+kunit_test_suite(iio_multiply_test_suite);
+
+MODULE_AUTHOR("Hans de Goede <hans@hansg.org>");
+MODULE_DESCRIPTION("Test IIO multiply functions");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_UNIT_TEST");
diff --git a/drivers/iio/test/iio-test-rescale.c b/drivers/iio/test/iio-test-rescale.c
new file mode 100644
index 000000000..bcd4a607b
--- /dev/null
+++ b/drivers/iio/test/iio-test-rescale.c
@@ -0,0 +1,719 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kunit tests for IIO rescale conversions
+ *
+ * Copyright (c) 2021 Liam Beguin <liambeguin@gmail.com>
+ */
+
+#include <linux/gcd.h>
+#include <linux/overflow.h>
+
+#include <linux/iio/afe/rescale.h>
+#include <linux/iio/iio.h>
+
+#include <kunit/test.h>
+
+struct rescale_tc_data {
+	const char *name;
+
+	const s32 numerator;
+	const s32 denominator;
+	const s32 offset;
+
+	const int schan_val;
+	const int schan_val2;
+	const int schan_off;
+	const int schan_scale_type;
+
+	const char *expected;
+	const char *expected_off;
+};
+
+static const struct rescale_tc_data scale_cases[] = {
+	/*
+	 * Typical use cases
+	 */
+	{
+		.name = "typical IIO_VAL_INT, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 42,
+		.expected = "5210.918114143",
+	},
+	{
+		.name = "typical IIO_VAL_INT, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 42,
+		.expected = "-5210.918114143",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 42,
+		.schan_val2 = 20,
+		.expected = "260.545905707",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 42,
+		.schan_val2 = 20,
+		.expected = "-260.545905707",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, positive",
+		.numerator = 42,
+		.denominator = 53,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "0.049528301",
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, negative",
+		.numerator = -42,
+		.denominator = 53,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "-0.049528301",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456,
+		.expected = "1240.710106203",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 1234,
+		.expected = "1240.84789",
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 1234,
+		.expected = "-1240.84789",
+	},
+	/*
+	 * Use cases with small scales involving divisions
+	 */
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 261/509 scaled by 90/1373754273",
+		.numerator = 261,
+		.denominator = 509,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 90,
+		.schan_val2 = 1373754273,
+		.expected = "0.000000033594",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 90/1373754273 scaled by 261/509",
+		.numerator = 90,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 261,
+		.schan_val2 = 509,
+		.expected = "0.000000033594",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 760/1373754273 scaled by 427/2727",
+		.numerator = 760,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 427,
+		.schan_val2 = 2727,
+		.expected = "0.000000086626",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 761/1373754273 scaled by 427/2727",
+		.numerator = 761,
+		.denominator = 1373754273,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 427,
+		.schan_val2 = 2727,
+		.expected = "0.000000086740",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 5/32768 scaled by 3/10000",
+		.numerator = 5,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 3,
+		.schan_val2 = 10000,
+		.expected = "0.0000000457763671875",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 0 < scale < 1",
+		.numerator = 6,
+		.denominator = 6,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, -1 < scale < 0",
+		.numerator = -6,
+		.denominator = 6,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "-0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, 0 < scale < 2",
+		.numerator = 8,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL, -2 < scale < 0",
+		.numerator = -8,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 1,
+		.schan_val2 = 3,
+		.expected = "-1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 760/32768 scaled by 15/22",
+		.numerator = 760,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 15,
+		.schan_val2 = 22,
+		.expected = "0.000000082946",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 761/32768 scaled by 15/22",
+		.numerator = 761,
+		.denominator = 32768,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 15,
+		.schan_val2 = 22,
+		.expected = "0.000000083055",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 0 < scale < 1",
+		.numerator = 16,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 4,
+		.expected = "0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, -1 < scale < 0",
+		.numerator = -16,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 4,
+		.expected = "-0.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, 0 < scale < 2",
+		.numerator = 8,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 1,
+		.expected = "1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_FRACTIONAL_LOG2, -2 < scale < 0",
+		.numerator = -8,
+		.denominator = 3,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 1,
+		.schan_val2 = 1,
+		.expected = "-1.3333333333333333",
+	},
+	{
+		.name = "small IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 5,
+		.schan_val2 = 1234,
+		.expected = "2.500617",
+	},
+	{
+		.name = "small IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1,
+		.denominator = 2,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 5,
+		.schan_val2 = 1234,
+		.expected = "-2.500617",
+	},
+	/*
+	 * INT_PLUS_{MICRO,NANO} positive/negative corner cases
+	 */
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, both negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, 3 negative",
+		.numerator = -1000000,
+		.denominator = -8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, 4 negative",
+		.numerator = -1000000,
+		.denominator = -8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = -123456,
+		.expected = "-1240.710106203",
+	},
+	{
+		.name = "negative IIO_VAL_INT_PLUS_NANO, negative, *val = 0",
+		.numerator = 1,
+		.denominator = -10,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 0,
+		.schan_val2 = 123456789,
+		.expected = "-0.012345678",
+	},
+	/*
+	 * INT_PLUS_{MICRO,NANO} decimal part overflow
+	 */
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "-1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = 123456789,
+		.expected = "-1256.01200856",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "16557.914267",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.expected = "-16557.914267",
+	},
+	{
+		.name = "decimal overflow IIO_VAL_INT_PLUS_MICRO, negative schan",
+		.numerator = 1000000,
+		.denominator = 8060,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = -10,
+		.schan_val2 = 123456789,
+		.expected = "-16557.914267",
+	},
+	/*
+	 * 32-bit overflow conditions
+	 */
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = S32_MAX,
+		.schan_val2 = 1,
+		.expected = "214748364.7",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = S32_MAX,
+		.schan_val2 = 1,
+		.expected = "-214748364.7",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL_LOG2, positive",
+		.numerator = S32_MAX,
+		.denominator = 4096,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 4096,
+		.schan_val2 = 16,
+		.expected = "32767.99998474121",
+	},
+	{
+		.name = "overflow IIO_VAL_FRACTIONAL_LOG2, negative",
+		.numerator = S32_MAX,
+		.denominator = 4096,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = -4096,
+		.schan_val2 = 16,
+		.expected = "-32767.99998474121",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "-1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_NANO, negative schan",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = -10,
+		.schan_val2 = S32_MAX,
+		.expected = "-1.214748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, positive",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "215.748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, negative",
+		.numerator = -2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = S32_MAX,
+		.expected = "-215.748364",
+	},
+	{
+		.name = "overflow IIO_VAL_INT_PLUS_MICRO, negative schan",
+		.numerator = 2,
+		.denominator = 20,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = -10,
+		.schan_val2 = S32_MAX,
+		.expected = "-215.748364",
+	},
+};
+
+static const struct rescale_tc_data offset_cases[] = {
+	/*
+	 * Typical use cases
+	 */
+	{
+		.name = "typical IIO_VAL_INT, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 123,
+		.schan_val2 = 0,
+		.schan_off = 14,
+		.expected_off = "24", /* 23.872 */
+	},
+	{
+		.name = "typical IIO_VAL_INT, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_INT,
+		.schan_val = 12,
+		.schan_val2 = 0,
+		.schan_off = 14,
+		.expected_off = "-88", /* -88.83333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 12,
+		.schan_val2 = 34,
+		.schan_off = 14,
+		.expected_off = "3510", /* 3510.333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL,
+		.schan_val = 12,
+		.schan_val2 = 34,
+		.schan_off = 14,
+		.expected_off = "-3482", /* -3482.333333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 12,
+		.schan_val2 = 16,
+		.schan_off = 14,
+		.expected_off = "6739299", /* 6739299.333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_FRACTIONAL_LOG2, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_FRACTIONAL_LOG2,
+		.schan_val = 12,
+		.schan_val2 = 16,
+		.schan_off = 14,
+		.expected_off = "-6739271", /* -6739271.333333333 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "135", /* 135.8951219647469 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_NANO, negative",
+		.offset = -1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_NANO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "-107", /* -107.89512196474689 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, positive",
+		.offset = 1234,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "23", /* 23.246438560723952 */
+	},
+	{
+		.name = "typical IIO_VAL_INT_PLUS_MICRO, negative",
+		.offset = -12345,
+		.schan_scale_type = IIO_VAL_INT_PLUS_MICRO,
+		.schan_val = 10,
+		.schan_val2 = 123456789,
+		.schan_off = 14,
+		.expected_off = "-78", /* -78.50185091745313 */
+	},
+};
+
+static void case_to_desc(const struct rescale_tc_data *t, char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(iio_rescale_scale, scale_cases, case_to_desc);
+KUNIT_ARRAY_PARAM(iio_rescale_offset, offset_cases, case_to_desc);
+
+/**
+ * iio_str_to_nano() - Parse a fixed-point string to get an
+ *                      IIO_VAL_INT_PLUS_NANO value
+ * @str: The string to parse
+ * @nano: The number as an integer
+ *
+ * Returns 0 on success, or a negative error code if the string cound not be
+ * parsed.
+ */
+static int iio_str_to_nano(const char *str, s64 *nano)
+{
+	int tmp, tmp2;
+	int ret = 0;
+
+	/*
+	 * iio_str_to_fixpoint() uses 10^8 here instead of 10^9 as fract_mult is
+	 * the multiplier for the first decimal place.
+	 */
+	ret = iio_str_to_fixpoint(str, 100000000, &tmp, &tmp2);
+	if (ret < 0)
+		return ret;
+
+	if (tmp < 0)
+		tmp2 *= -1;
+
+	*nano = (s64)tmp * 1000000000UL + tmp2;
+
+	return ret;
+}
+
+/**
+ * iio_test_relative_error_ppm() - Compute relative error (in parts-per-million)
+ *                                 between two fixed-point strings
+ * @real_str: The real value as a string
+ * @exp_str: The expected value as a string
+ *
+ * Returns a negative error code if the strings cound not be parsed, or the
+ * relative error in parts-per-million.
+ */
+static int iio_test_relative_error_ppm(const char *real_str, const char *exp_str)
+{
+	s64 real, exp, err;
+	int ret;
+
+	ret = iio_str_to_nano(real_str, &real);
+	if (ret < 0)
+		return ret;
+
+	ret = iio_str_to_nano(exp_str, &exp);
+	if (ret < 0)
+		return ret;
+
+	if (!exp) {
+		pr_err("Expected value is null, relative error is undefined\n");
+		return -EINVAL;
+	}
+
+	err = 1000000UL * abs(exp - real);
+
+	return (int)div64_u64(err, abs(exp));
+}
+
+static void iio_rescale_test_scale(struct kunit *test)
+{
+	struct rescale_tc_data *t = (struct rescale_tc_data *)test->param_value;
+	char *buff = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	struct rescale rescale;
+	int values[2];
+	int rel_ppm;
+	int ret;
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buff);
+
+	rescale.numerator = t->numerator;
+	rescale.denominator = t->denominator;
+	rescale.offset = t->offset;
+	values[0] = t->schan_val;
+	values[1] = t->schan_val2;
+
+	ret = rescale_process_scale(&rescale, t->schan_scale_type,
+				    &values[0], &values[1]);
+
+	ret = iio_format_value(buff, ret, 2, values);
+	KUNIT_EXPECT_EQ(test, (int)strlen(buff), ret);
+
+	rel_ppm = iio_test_relative_error_ppm(buff, t->expected);
+	KUNIT_EXPECT_GE_MSG(test, rel_ppm, 0, "failed to compute ppm\n");
+
+	KUNIT_EXPECT_EQ_MSG(test, rel_ppm, 0,
+			    "\t    real=%s"
+			    "\texpected=%s\n",
+			    buff, t->expected);
+}
+
+static void iio_rescale_test_offset(struct kunit *test)
+{
+	struct rescale_tc_data *t = (struct rescale_tc_data *)test->param_value;
+	char *buff_off = kunit_kmalloc(test, PAGE_SIZE, GFP_KERNEL);
+	struct rescale rescale;
+	int values[2];
+	int ret;
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buff_off);
+
+	rescale.numerator = t->numerator;
+	rescale.denominator = t->denominator;
+	rescale.offset = t->offset;
+	values[0] = t->schan_val;
+	values[1] = t->schan_val2;
+
+	ret = rescale_process_offset(&rescale, t->schan_scale_type,
+				     t->schan_val, t->schan_val2, t->schan_off,
+				     &values[0], &values[1]);
+
+	ret = iio_format_value(buff_off, ret, 2, values);
+	KUNIT_EXPECT_EQ(test, (int)strlen(buff_off), ret);
+
+	KUNIT_EXPECT_STREQ(test, strim(buff_off), t->expected_off);
+}
+
+static struct kunit_case iio_rescale_test_cases[] = {
+	KUNIT_CASE_PARAM(iio_rescale_test_scale, iio_rescale_scale_gen_params),
+	KUNIT_CASE_PARAM(iio_rescale_test_offset, iio_rescale_offset_gen_params),
+	{ }
+};
+
+static struct kunit_suite iio_rescale_test_suite = {
+	.name = "iio-rescale",
+	.test_cases = iio_rescale_test_cases,
+};
+kunit_test_suite(iio_rescale_test_suite);
+
+MODULE_AUTHOR("Liam Beguin <liambeguin@gmail.com>");
+MODULE_DESCRIPTION("Test IIO rescale conversion functions");
+MODULE_LICENSE("GPL v2");
+MODULE_IMPORT_NS("IIO_RESCALE");