[PATCH v3 0/3] driver core: remove software node from platform devices on device release

[PATCH v3 0/3] driver core: remove software node from platform devices on device release

[Bartosz Golaszewski]

This fixes an issue in platform device code where, if we specify a
software node for a platform device using struct platform_device_info,
it will not be removed on device .release().

The second patch adds a new kunit helper which is used in patch 3/3 that
adds a test-case that can be used to reproduce the problem and prove that
the fix works as well as another making sure a corner case of using a
software node as the primary firmware node works too.

Merging strategy: patch 1/3 should go into v7.1. Once it's upstream, the
first tag containing it should be pulled into the driver core tree and
the remaining patches applied on top with an ack from the kunit
maintainers.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
Changes in v3:
- Make sure the reference of the primary software node we possibly take,
  is always released by moving the get() before calls that may fail
- Don't allow passing two software nodes
- Add a test case for that situation
- Link to v2: https://patch.msgid.link/20260423-swnode-remove-on-dev-unreg-v2-0-0e5213cde2ed@oss.qualcomm.com

Changes in v2:
- Change the order between removing the software node and dropping the
  reference to the device's OF node
- Address a situation where a software node is used as the primary
  firmware node
- Add a patch adding a new kunit helper
- Add another test case
- Link to v1: https://patch.msgid.link/20260410-swnode-remove-on-dev-unreg-v1-0-cd7d305f3db2@oss.qualcomm.com

---
Bartosz Golaszewski (3):
      driver core: platform: remove software node on release()
      kunit: provide kunit_software_node_register()
      driver core: platform: tests: add test cases for correct swnode removal

 drivers/base/platform.c                  |  17 +++-
 drivers/base/test/platform-device-test.c | 156 +++++++++++++++++++++++++++++++
 include/kunit/fwnode.h                   |  19 ++++
 lib/kunit/Makefile                       |   3 +-
 lib/kunit/fwnode.c                       |  52 +++++++++++
 5 files changed, 245 insertions(+), 2 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260410-swnode-remove-on-dev-unreg-42bfc4b23ba8

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

[PATCH v3 1/3] driver core: platform: remove software node on release()

[Bartosz Golaszewski]

If we pass a software node to a newly created device using struct
platform_device_info, it will not be removed when the device is
released. This may happen when a module creating the device is removed
or on failure in platform_device_add().

When we try to reuse that software node in a subsequent call to
platform_device_register_full(), it will fails with -EBUSY. Add the
missing call to device_remove_software_node() in release path.

In addition to the above change, make sure that we still function
correctly if a software node is used as the primary firmware node as
well as disallow using two software nodes for platform devices as
device_add_software_node() does not handle this case correctly (in fact
a comment inside it states that only one software node per device is
allowed but it will not bail out if two are used so we need to handle it
here).

Fixes: 0fc434bc2c45 ("driver core: platform: allow attaching software nodes when creating devices")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/base/platform.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 75b4698d0e582e67adafa78c312d75c72fd654cf..a6268a72a99e864cbfc333cd99c0d5706b901ff3 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -599,6 +599,7 @@ static void platform_device_release(struct device *dev)
 	struct platform_object *pa = container_of(dev, struct platform_object,
 						  pdev.dev);
 
+	device_remove_software_node(dev);
 	of_node_put(pa->pdev.dev.of_node);
 	kfree(pa->pdev.dev.platform_data);
 	kfree(pa->pdev.mfd_cell);
@@ -848,7 +849,11 @@ struct platform_device *platform_device_register_full(const struct platform_devi
 	int ret;
 	struct platform_device *pdev;
 
-	if (pdevinfo->swnode && pdevinfo->properties)
+	/*
+	 * Only one software node per device is allowed. Make sure we don't
+	 * accept or create two.
+	 */
+	if (pdevinfo->swnode && (pdevinfo->properties || is_software_node(pdevinfo->fwnode)))
 		return ERR_PTR(-EINVAL);
 
 	pdev = platform_device_alloc(pdevinfo->name, pdevinfo->id);
@@ -866,6 +871,16 @@ struct platform_device *platform_device_register_full(const struct platform_devi
 		pdev->dev.coherent_dma_mask = pdevinfo->dma_mask;
 	}
 
+	/*
+	 * If the primary firmware node is a software node and there's no
+	 * secondary firmware node, the primary will be affected by the call
+	 * to device_remove_software_node() in platform_device_release() and
+	 * its reference count will be dropped by one. Take another reference
+	 * here to make it have no effect.
+	 */
+	if (is_software_node(pdevinfo->fwnode) && !pdevinfo->swnode)
+		fwnode_handle_get(pdevinfo->fwnode);
+
 	ret = platform_device_add_resources(pdev, pdevinfo->res, pdevinfo->num_res);
 	if (ret)
 		goto err;

-- 
2.47.3

[PATCH v3 2/3] kunit: provide kunit_software_node_register()

[Bartosz Golaszewski]

Implement a helper for registering kunit test-managed software nodes.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 include/kunit/fwnode.h | 19 ++++++++++++++++++
 lib/kunit/Makefile     |  3 ++-
 lib/kunit/fwnode.c     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/include/kunit/fwnode.h b/include/kunit/fwnode.h
new file mode 100644
index 0000000000000000000000000000000000000000..e1554ace64b8a5899aff9f4b4247e5157826a49b
--- /dev/null
+++ b/include/kunit/fwnode.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit resource management helpers firmware nodes.
+ *
+ * Copyright (C) Qualcomm Technologies, Inc. and/or its subsidiaries
+ */
+
+#ifndef _KUNIT_FWNODE_H
+#define _KUNIT_FWNODE_H
+
+struct kunit;
+struct fwnode_handle;
+struct software_node;
+
+struct fwnode_handle *
+kunit_software_node_register(struct kunit *test,
+			     const struct software_node *node);
+
+#endif /* _KUNIT_FWNODE_H */
diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 656f1fa35abcc635e67d5b4cb1bc586b48415ac5..7549a701791b5b7eaa8e0637b6818cdfd0b655a8 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -10,7 +10,8 @@ kunit-objs +=				test.o \
 					executor.o \
 					attributes.o \
 					device.o \
-					platform.o
+					platform.o \
+					fwnode.o
 
 ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
diff --git a/lib/kunit/fwnode.c b/lib/kunit/fwnode.c
new file mode 100644
index 0000000000000000000000000000000000000000..bc8bf06762dd71a741a3419c1ca04028d6ad3ec8
--- /dev/null
+++ b/lib/kunit/fwnode.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Qualcomm Technologies, Inc. and/or its subsidiaries
+ */
+
+#include <kunit/fwnode.h>
+#include <kunit/test.h>
+
+#include <linux/fwnode.h>
+#include <linux/property.h>
+
+static void kunit_software_node_unregister(void *data)
+{
+	const struct software_node *swnode = data;
+
+	software_node_unregister(swnode);
+}
+
+/**
+ * kunit_software_node_register() - Register a KUnit-managed software node
+ * @test: test context
+ * @swnode: Software node to register
+ *
+ * Register a test-managed software node and return its firmware node handle.
+ * The software node is unregistered after the test case completes.
+ *
+ * Return: Firmware node handle of the registered software node or IS_ERR()
+ * on failure.
+ */
+struct fwnode_handle *
+kunit_software_node_register(struct kunit *test,
+			     const struct software_node *swnode)
+{
+	struct fwnode_handle *fwnode;
+	int ret;
+
+	ret = software_node_register(swnode);
+	if (ret)
+		return ERR_PTR(ret);
+
+	fwnode = software_node_fwnode(swnode);
+	if (WARN_ON(!fwnode))
+		return ERR_PTR(-ENOENT);
+
+	ret = kunit_add_action_or_reset(test, kunit_software_node_unregister,
+					(void *)swnode);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return fwnode;
+}
+EXPORT_SYMBOL_GPL(kunit_software_node_register);

-- 
2.47.3

[PATCH v3 3/3] driver core: platform: tests: add test cases for correct swnode removal

[Bartosz Golaszewski]

Extend the kunit module for platform devices with test cases verifying
that the same software node can be added to platform devices repeatedly.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/base/test/platform-device-test.c | 156 +++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)

diff --git a/drivers/base/test/platform-device-test.c b/drivers/base/test/platform-device-test.c
index 6355a2231b741791b54eb78af42e13f31f745184..19b3b2ea150738877278f7e37be7ef69539147c0 100644
--- a/drivers/base/test/platform-device-test.c
+++ b/drivers/base/test/platform-device-test.c
@@ -1,12 +1,15 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#include <kunit/fwnode.h>
 #include <kunit/platform_device.h>
 #include <kunit/resource.h>
 
 #include <linux/device.h>
 #include <linux/device/bus.h>
+#include <linux/fwnode.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 
 #define DEVICE_NAME "test"
 
@@ -253,9 +256,162 @@ static struct kunit_suite platform_device_match_test_suite = {
 	.test_cases = platform_device_match_tests,
 };
 
+static int platform_device_swnode_test_probe(struct platform_device *pdev)
+{
+	return 0;
+}
+
+static struct platform_driver platform_swnode_test_driver = {
+	.probe = platform_device_swnode_test_probe,
+	.driver = {
+		.name = DEVICE_NAME,
+	},
+};
+
+static const struct software_node platform_device_test_swnode = { };
+
+/*
+ * Check that reusing a software node works correctly. If the call to
+ * platform_device_register_full() fails after adding the secondary firmware
+ * node, the software node must be unregistered in the device's release()
+ * callback or the subsequent call to platform_device_register_full() will fail
+ * with -EBUSY due to the software node aleady having been registered.
+ */
+static void platform_device_swnode_add_twice(struct kunit *test)
+{
+	struct platform_device_info pdevinfo;
+	struct platform_device *pdev;
+	struct fwnode_handle fwnode;
+	int ret;
+
+	ret = kunit_platform_driver_register(test, &platform_swnode_test_driver);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	fwnode_init(&fwnode, NULL);
+	pdevinfo = (struct platform_device_info){
+		.name = DEVICE_NAME,
+		.id = PLATFORM_DEVID_NONE,
+		.fwnode = &fwnode,
+		.swnode = &platform_device_test_swnode,
+	};
+
+	pdev = platform_device_register_full(&pdevinfo);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	wait_for_device_probe();
+	KUNIT_ASSERT_TRUE(test, device_is_bound(&pdev->dev));
+
+	platform_device_unregister(pdev);
+
+	pdev = platform_device_register_full(&pdevinfo);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	wait_for_device_probe();
+	KUNIT_ASSERT_TRUE(test, device_is_bound(&pdev->dev));
+
+	platform_device_unregister(pdev);
+}
+
+/*
+ * Check that passing a software node as the primary firmware node of the
+ * platform device does not result in it being unregistered by the call to
+ * device_remove_software_node() in its release path.
+ */
+static void platform_device_swnode_as_primary(struct kunit *test)
+{
+	struct platform_device_info pdevinfo;
+	struct platform_device *pdev;
+	struct fwnode_handle *fwnode;
+	int ret;
+
+	ret = kunit_platform_driver_register(test, &platform_swnode_test_driver);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	fwnode = kunit_software_node_register(test, &platform_device_test_swnode);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fwnode);
+
+	pdevinfo = (struct platform_device_info){
+		.name = DEVICE_NAME,
+		.id = PLATFORM_DEVID_NONE,
+		.fwnode = fwnode,
+	};
+
+	pdev = platform_device_register_full(&pdevinfo);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	wait_for_device_probe();
+	KUNIT_ASSERT_TRUE(test, device_is_bound(&pdev->dev));
+
+	platform_device_unregister(pdev);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, software_node_fwnode(&platform_device_test_swnode));
+}
+
+static const struct software_node platform_device_test_primary_swnode = { };
+
+/*
+ * Check that passing two software nodes to platform_device_register_full()
+ * fails.
+ */
+static void platform_device_two_swnodes(struct kunit *test)
+{
+	static const struct property_entry properties[] = {
+		PROPERTY_ENTRY_U32("foo", 42),
+		{ }
+	};
+
+	struct platform_device_info pdevinfo;
+	struct platform_device *pdev;
+	struct fwnode_handle *fwnode;
+	int ret;
+
+	ret = kunit_platform_driver_register(test, &platform_swnode_test_driver);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	fwnode = kunit_software_node_register(test, &platform_device_test_swnode);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fwnode);
+
+	pdevinfo = (struct platform_device_info){
+		.name = DEVICE_NAME,
+		.id = PLATFORM_DEVID_NONE,
+		.fwnode = fwnode,
+		.swnode = &platform_device_test_swnode,
+	};
+
+	pdev = platform_device_register_full(&pdevinfo);
+	KUNIT_ASSERT_TRUE(test, IS_ERR(pdev));
+	KUNIT_ASSERT_EQ_MSG(test, PTR_ERR(pdev), -EINVAL,
+			    "Expected errno == -EINVAL, got: %pe", pdev);
+
+	pdevinfo = (struct platform_device_info){
+		.name = DEVICE_NAME,
+		.id = PLATFORM_DEVID_NONE,
+		.swnode = &platform_device_test_swnode,
+		.properties = properties,
+	};
+
+	pdev = platform_device_register_full(&pdevinfo);
+	KUNIT_ASSERT_TRUE(test, IS_ERR(pdev));
+	KUNIT_ASSERT_EQ_MSG(test, PTR_ERR(pdev), -EINVAL,
+			    "Expected errno == -EINVAL, got: %pe", pdev);
+}
+
+static struct kunit_case platform_device_swnode_tests[] = {
+	KUNIT_CASE(platform_device_swnode_add_twice),
+	KUNIT_CASE(platform_device_swnode_as_primary),
+	KUNIT_CASE(platform_device_two_swnodes),
+	{}
+};
+
+static struct kunit_suite platform_device_swnode_test_suite = {
+	.name = "platform-device-swnode",
+	.test_cases = platform_device_swnode_tests,
+};
+
 kunit_test_suites(
 	&platform_device_devm_test_suite,
 	&platform_device_match_test_suite,
+	&platform_device_swnode_test_suite,
 );
 
 MODULE_DESCRIPTION("Test module for platform devices");

-- 
2.47.3

Re: [PATCH v3 1/3] driver core: platform: remove software node on release()

[Andy Shevchenko]

On Tue, Apr 28, 2026 at 11:20:26AM +0200, Bartosz Golaszewski wrote:
> If we pass a software node to a newly created device using struct
> platform_device_info, it will not be removed when the device is
> released. This may happen when a module creating the device is removed
> or on failure in platform_device_add().
> 
> When we try to reuse that software node in a subsequent call to
> platform_device_register_full(), it will fails with -EBUSY. Add the
> missing call to device_remove_software_node() in release path.
> 
> In addition to the above change, make sure that we still function
> correctly if a software node is used as the primary firmware node as
> well as disallow using two software nodes for platform devices as
> device_add_software_node() does not handle this case correctly (in fact
> a comment inside it states that only one software node per device is
> allowed but it will not bail out if two are used so we need to handle it
> here).

...

> +	device_remove_software_node(dev);
>  	of_node_put(pa->pdev.dev.of_node);

So, why do we decide not to convert this to fwnode_handle_put() (and respective
_get() elsewhere)?

...

> +	/*
> +	 * Only one software node per device is allowed. Make sure we don't
> +	 * accept or create two.
> +	 */
> +	if (pdevinfo->swnode && (pdevinfo->properties || is_software_node(pdevinfo->fwnode)))
>  		return ERR_PTR(-EINVAL);

^^^ left for the context.

...

> +	/*
> +	 * If the primary firmware node is a software node and there's no
> +	 * secondary firmware node, the primary will be affected by the call
> +	 * to device_remove_software_node() in platform_device_release() and
> +	 * its reference count will be dropped by one. Take another reference
> +	 * here to make it have no effect.
> +	 */
> +	if (is_software_node(pdevinfo->fwnode) && !pdevinfo->swnode)
> +		fwnode_handle_get(pdevinfo->fwnode);

IIUC the `is_software_node(pdevinfo->fwnode) && pdevinfo->swnode` may not
happen here due to the above check. If I haven't missed anything, this check
is simply

	if (is_software_node(pdevinfo->fwnode))

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 1/3] driver core: platform: remove software node on release()

[Bartosz Golaszewski]

On Tue, Apr 28, 2026 at 1:10 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Tue, Apr 28, 2026 at 11:20:26AM +0200, Bartosz Golaszewski wrote:
> > If we pass a software node to a newly created device using struct
> > platform_device_info, it will not be removed when the device is
> > released. This may happen when a module creating the device is removed
> > or on failure in platform_device_add().
> >
> > When we try to reuse that software node in a subsequent call to
> > platform_device_register_full(), it will fails with -EBUSY. Add the
> > missing call to device_remove_software_node() in release path.
> >
> > In addition to the above change, make sure that we still function
> > correctly if a software node is used as the primary firmware node as
> > well as disallow using two software nodes for platform devices as
> > device_add_software_node() does not handle this case correctly (in fact
> > a comment inside it states that only one software node per device is
> > allowed but it will not bail out if two are used so we need to handle it
> > here).
>
> ...
>
> > +     device_remove_software_node(dev);
> >       of_node_put(pa->pdev.dev.of_node);
>
> So, why do we decide not to convert this to fwnode_handle_put() (and respective
> _get() elsewhere)?
>

Yes, I'll do it separately, I don't want to shove too much stuff into
this bugfix.

> ...
>
> > +     /*
> > +      * Only one software node per device is allowed. Make sure we don't
> > +      * accept or create two.
> > +      */
> > +     if (pdevinfo->swnode && (pdevinfo->properties || is_software_node(pdevinfo->fwnode)))
> >               return ERR_PTR(-EINVAL);
>
> ^^^ left for the context.
>
> ...
>
> > +     /*
> > +      * If the primary firmware node is a software node and there's no
> > +      * secondary firmware node, the primary will be affected by the call
> > +      * to device_remove_software_node() in platform_device_release() and
> > +      * its reference count will be dropped by one. Take another reference
> > +      * here to make it have no effect.
> > +      */
> > +     if (is_software_node(pdevinfo->fwnode) && !pdevinfo->swnode)
> > +             fwnode_handle_get(pdevinfo->fwnode);
>
> IIUC the `is_software_node(pdevinfo->fwnode) && pdevinfo->swnode` may not
> happen here due to the above check. If I haven't missed anything, this check
> is simply
>

Right, it can be a simple is_software_node(pdevinfo->fwnode).

Bart

Re: [PATCH v3 1/3] driver core: platform: remove software node on release()

[Andy Shevchenko]

On Tue, Apr 28, 2026 at 01:16:30PM +0200, Bartosz Golaszewski wrote:
> On Tue, Apr 28, 2026 at 1:10 PM Andy Shevchenko
> <andriy.shevchenko@intel.com> wrote:
> > On Tue, Apr 28, 2026 at 11:20:26AM +0200, Bartosz Golaszewski wrote:

...

> > > +     device_remove_software_node(dev);
> > >       of_node_put(pa->pdev.dev.of_node);
> >
> > So, why do we decide not to convert this to fwnode_handle_put() (and respective
> > _get() elsewhere)?
> 
> Yes, I'll do it separately, I don't want to shove too much stuff into
> this bugfix.

Ah, good!

...

> > > +     /*
> > > +      * If the primary firmware node is a software node and there's no
> > > +      * secondary firmware node, the primary will be affected by the call
> > > +      * to device_remove_software_node() in platform_device_release() and
> > > +      * its reference count will be dropped by one. Take another reference
> > > +      * here to make it have no effect.
> > > +      */
> > > +     if (is_software_node(pdevinfo->fwnode) && !pdevinfo->swnode)
> > > +             fwnode_handle_get(pdevinfo->fwnode);
> >
> > IIUC the `is_software_node(pdevinfo->fwnode) && pdevinfo->swnode` may not
> > happen here due to the above check. If I haven't missed anything, this check
> > is simply
> 
> Right, it can be a simple is_software_node(pdevinfo->fwnode).

With that being addressed, the rest LGTM,

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

(also assuming we will have at some point the above mentioned amendment).

-- 
With Best Regards,
Andy Shevchenko