iio: test: test gain-time-scale helpers

Some light sensors can adjust both the HW-gain and integration time.
There are cases where adjusting the integration time has similar impact
to the scale of the reported values as gain setting has.

IIO users do typically expect to handle scale by a single writable 'scale'
entry. Driver should then adjust the gain/time accordingly.

It however is difficult for a driver to know whether it should change
gain or integration time to meet the requested scale. Usually it is
preferred to have longer integration time which usually improves
accuracy, but there may be use-cases where long measurement times can be
an issue. Thus it can be preferable to allow also changing the
integration time - but mitigate the scale impact by also changing the gain
underneath. Eg, if integration time change doubles the measured values,
the driver can reduce the HW-gain to half.

The theory of the computations of gain-time-scale is simple. However,
some people (undersigned) got that implemented wrong for more than once.
Hence some gain-time-scale helpers were introduced.

Add some simple tests to verify the most hairy functions.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Link: https://lore.kernel.org/r/0f7505b43f91394dc3bb636369489c897b7e01a7.1705328293.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: test: format: follow CONFIG_ naming convention

The KUnit documentation indicates that all KUnit Kconfig entries must
match CONFIG_<name>_KUNIT_TEST: where <name> is the name of the test
suite. Rename the IIO_TEST_FORMAT configuration accordingly.

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Link: https://lore.kernel.org/r/20220710013109.3349104-4-liambeguin@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: test: fix missing MODULE_LICENSE for IIO_RESCALE=m

When IIO_RESCALE_KUNIT_TEST=y and IIO_RESCALE=m,
drivers/iio/afe/iio-rescale.o is built twice causing the
MODULE_LICENSE() to be lost, as shown by:

ERROR: modpost: missing MODULE_LICENSE() in drivers/iio/afe/iio-rescale.o

Rework the build configuration to have the dependency specified in the
Kconfig.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: 8e74a48d17d5 ("iio: test: add basic tests for the iio-rescale driver")
Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20220601142138.3331278-1-liambeguin@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio: test: add basic tests for the iio-rescale driver

The iio-rescale driver supports various combinations of scale types and
offsets. These can often result in large integer multiplications. Make
sure these calculations are done right by adding a set of kunit test
cases that build on top of iio-test-format.

To run these tests, add the following to .kunitconfig
$ cat .kunitconfig
CONFIG_IIO=y
CONFIG_IIO_RESCALE_KUNIT_TEST=y
CONFIG_KUNIT=y

Then run:
$ ./tools/testing/kunit/kunit.py run --kunitconfig .kunitconfig

Signed-off-by: Liam Beguin <liambeguin@gmail.com>
Reviewed-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220213025739.2561834-7-liambeguin@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio/test-format: build kunit tests without structleak plugin

The structleak plugin causes the stack frame size to grow immensely when
used with KUnit:

../drivers/iio/test/iio-test-format.c: In function ‘iio_test_iio_format_value_fixedpoint’:
../drivers/iio/test/iio-test-format.c:98:1: warning: the frame size of 2336 bytes is larger than 2048 bytes [-Wframe-larger-than=]

Turn it off in this file.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

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.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>