Re: [PATCH v3 4/9] platform/wmi: Add kunit test for the string conversion code

[Armin Wolf]

Am 12.01.26 um 17:34 schrieb Ilpo Järvinen:

> On Fri, 9 Jan 2026, Armin Wolf wrote:
>
> > The string conversion frunctions provided by the WMI driver core
> > have no dependencies on the remaining WMI API, making them suitable
> > for unit tests.
> >
> > Implement such a unit test using kunit. Those unit tests verify that
> > converting between WMI strings and UTF8 strings works as expected.
> > They also verify that edge cases are handled correctly.
> >
> > Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> > ---
> >   drivers/platform/wmi/tests/Kconfig        |  11 +
> >   drivers/platform/wmi/tests/Makefile       |   3 +
> >   drivers/platform/wmi/tests/string_kunit.c | 278 ++++++++++++++++++++++
> >   3 files changed, 292 insertions(+)
> >   create mode 100644 drivers/platform/wmi/tests/string_kunit.c
> >
> > diff --git a/drivers/platform/wmi/tests/Kconfig b/drivers/platform/wmi/tests/Kconfig
> > index efcbcb51c251..f7f0f3c540f5 100644
> > --- a/drivers/platform/wmi/tests/Kconfig
> > +++ b/drivers/platform/wmi/tests/Kconfig
> > @@ -14,3 +14,14 @@ config ACPI_WMI_MARSHALLING_KUNIT_TEST
> >   	  to the KUnit documentation in Documentation/dev-tools/kunit/.
> >   
> >   	  If unsure, say N.
> > +
> > +config ACPI_WMI_STRING_KUNIT_TEST
> > +	tristate "KUnit Test for ACPI-WMI string conversion" if !KUNIT_ALL_TESTS
> > +	depends on KUNIT
> > +	default KUNIT_ALL_TESTS
> > +	help
> > +	  This builds unit tests for the ACPI-WMI string conversion 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.
> > diff --git a/drivers/platform/wmi/tests/Makefile b/drivers/platform/wmi/tests/Makefile
> > index 252c3125353a..62c438e26259 100644
> > --- a/drivers/platform/wmi/tests/Makefile
> > +++ b/drivers/platform/wmi/tests/Makefile
> > @@ -6,3 +6,6 @@
> >   
> >   wmi_marshalling_kunit-y				:= marshalling_kunit.o
> >   obj-$(CONFIG_ACPI_WMI_MARSHALLING_KUNIT_TEST)	+= wmi_marshalling_kunit.o
> > +
> > +wmi_string_kunit-y				:= string_kunit.o
> > +obj-$(CONFIG_ACPI_WMI_STRING_KUNIT_TEST)	+= wmi_string_kunit.o
> > diff --git a/drivers/platform/wmi/tests/string_kunit.c b/drivers/platform/wmi/tests/string_kunit.c
> > new file mode 100644
> > index 000000000000..9aa3ffa85090
> > --- /dev/null
> > +++ b/drivers/platform/wmi/tests/string_kunit.c
> > @@ -0,0 +1,278 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * KUnit test for the ACPI-WMI string conversion code.
> > + *
> > + * Copyright (C) 2025 Armin Wolf <W_Armin@xxxxxx>
> > + */
> > +
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/string.h>
> > +#include <linux/wmi.h>
> > +
> > +#include <kunit/resource.h>
> > +#include <kunit/test.h>
> > +
> > +#include <asm/byteorder.h>
> > +
> > +struct wmi_string_param {
> > +	const char *name;
> > +	const struct wmi_string *wmi_string;
> > +	/*
> > +	 * Remember that using sizeof() on a struct wmi_string will
> > +	 * always return a size of two bytes due to the flexible
> > +	 * array member!
> > +	 */
> > +	size_t wmi_string_length;
> > +	const u8 *utf8_string;
> > +	size_t utf8_string_length;
> > +};
> > +
> > +#define TEST_WMI_STRING_LENGTH 12
> > +
> > +static const struct wmi_string test_wmi_string = {
> > +	.length = cpu_to_le16(10),
> > +	.chars = {
> > +		cpu_to_le16(u'T'),
> I've applied this to for-next and intend to keep these there but FYI these
> trigger sparse errors. I don't know if they're fixable or not with
> reasonable effort on kernel side.

To me it seems that sparse ignores the u-prefix signaling that the character constant
has a length of 16-bits, but good catch.

If this really is a problem then gcc would issue a warning anyway (happened when i was
using the 🐧 character which does not fit into a 16-bit character constant).

Thanks,
Armin Wolf

> $ sparse --version
> 0.6.4 (Debian: 0.6.4-3)
>
> --
>   i.