[PATCH v6 3/7] kunit: Add kunit wrappers for (root) device creation

Matti Vaittinen
2023-03-27T11:34:18Z

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A few tests need to have a valid struct device. One such example is
tests which want to be testing devm-managed interfaces.

Add kunit wrapper for root_device_[un]register(), which create a root
device and also add a kunit managed clean-up routine for the device
destruction upon test exit.

Special note: In some cases the device reference-count does not reach
zero and devm-unwinding is not done if device is not sitting on a bus.
The root_device_[un]register() are dealing with such devices and thus
this interface may not be usable by all in its current form. More
information can be found from:
https://lore.kernel.org/dri-devel/20221117165311.vovrc7usy4efiytl@houat/

The use of root-devices in the kunit helpers is intended to be an
intermediate solution to allow tests which do not require device to sit
on a bus avoid directly abusing the root_device_[un]register() while
proper kunit device solution is being worked on. Related discussion can be
found from:
https://lore.kernel.org/lkml/CABVgOSmx3A4Vwos2_8xO-XQrQAw5gvY0nc5zLpLmcJ7FtA-dTQ@mail.gmail.com/

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---
Change history:
v5 => v6:
- Kunit resource-managed root_device creation wrapper (new patch)

Please note: This patch uses root-devices (as was suggested) until there
is a proper dummy device creation mechanism added in kunit. The root
devices are embedded in kunit wrappers to simplify replacing the
root-devices with proper solution when it is available.

David Gow has sent out an RFC[1] which should implement these helpers
using not-yet-in-tree deferring API. This RFC aims to support
kunit_device which should be _the right thing to do_. I added this
implementation here because it may (or may not) take a while for the David's
RFC to make it's way in-kernel. So, in order to not delay this series I
added these helpers which use the existing kunit resource management for
clean-up while the new deferring kunit API is not yet in place.

[1] https://lore.kernel.org/linux-kselftest/20230325043104.3761770-1-davidgow@google.com/T/#mf797239a8bce11630875fdf60aab9ed627add1f0

---
include/kunit/device.h | 18 ++++++++++++++++++
lib/kunit/Makefile | 3 ++-
lib/kunit/device.c | 36 ++++++++++++++++++++++++++++++++++++
3 files changed, 56 insertions(+), 1 deletion(-)
create mode 100644 include/kunit/device.h
create mode 100644 lib/kunit/device.c

diff --git a/include/kunit/device.h b/include/kunit/device.h
new file mode 100644
index 000000000000..f02740b7583b
--- /dev/null
+++ b/include/kunit/device.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __KUNIT_DEVICE_H__
+#define __KUNIT_DEVICE_H__
+
+#include <kunit/test.h>
+
+struct device;
+
+/* Register a new device against a KUnit test. */
+struct device *kunit_device_register(struct kunit *test, const char *name);
+/*
+ * Unregister a device created by kunit_device_register() early (i.e.,
+ * before test cleanup).
+ */
+void kunit_device_unregister(struct kunit *test, struct device *dev);
+
+#endif
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index cb417f504996..64449549b990 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -6,7 +6,8 @@ kunit-objs += test.o \
string-stream.o \
assert.o \
try-catch.o \
- executor.o
+ executor.o \
+ device.o

ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
kunit-objs += debugfs.o
diff --git a/lib/kunit/device.c b/lib/kunit/device.c
new file mode 100644
index 000000000000..425f6d62ebd7
--- /dev/null
+++ b/lib/kunit/device.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <kunit/device.h>
+#include <kunit/test.h>
+
+#include <linux/device.h>
+
+static void kunit_device_drop(struct kunit_resource *res)
+{
+ root_device_unregister(res->data);
+}
+
+struct device *kunit_device_register(struct kunit *test, const char *name)
+{
+ struct device *dev;
+
+ dev = root_device_register(name);
+ if (IS_ERR_OR_NULL(dev))
+ return dev;
+
+ return kunit_alloc_resource(test, NULL, kunit_device_drop, GFP_KERNEL,
+ dev);
+}
+EXPORT_SYMBOL_GPL(kunit_device_register);
+
+static bool kunit_device_match(struct kunit *test, struct kunit_resource *res,
+ void *match_data)
+{
+ return res->data == match_data;
+}
+
+void kunit_device_unregister(struct kunit *test, struct device *dev)
+{
+ kunit_destroy_resource(test, kunit_device_match, dev);
+}
+EXPORT_SYMBOL_GPL(kunit_device_unregister);
--
2.39.2

--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]

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