[PATCH] driver core: platform: tests: add a shared software node test case

[PATCH] driver core: platform: tests: add a shared software node test case

[Stuart Summers]

Cover the pattern used by drm/xe + i2c-designware, where a software node
assigned as a platform device's primary firmware node is handed to a
second device via device_set_node(), and make sure removing that second
device leaves the owner's node intact.

A potential fix for this issue in the drm/xe driver is being discussed
in [1].

The signature in this case looks like this:
Oops: general protection fault, probably for non-canonical address
0x6b6b6b6b6b6b6b73
RIP: platform_device_release+0x6f/0x80

Signed-off-by: Stuart Summers <stuart.summers@intel.com>
Assisted-by: LLM

[1]: https://patchwork.freedesktop.org/series/175858/
---
 drivers/base/test/platform-device-test.c | 57 ++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/base/test/platform-device-test.c b/drivers/base/test/platform-device-test.c
index 9ce563f76aad..378ba7fab2ac 100644
--- a/drivers/base/test/platform-device-test.c
+++ b/drivers/base/test/platform-device-test.c
@@ -420,9 +420,66 @@ static void platform_device_two_swnodes(struct kunit *test)
 			    "Expected errno == -EINVAL, got: %pe", pdev);
 }
 
+static void platform_device_swnode_sharer_release(struct device *dev)
+{
+}
+
+/*
+ * A software node assigned as a platform device's primary firmware node may be
+ * shared with other devices: i2c-designware passes dev_fwnode() of its platform
+ * device down to the i2c adapter device it creates. Check that removing the
+ * sharing device leaves the owner's software node intact.
+ */
+static void platform_device_swnode_shared(struct kunit *test)
+{
+	static const struct property_entry properties[] = {
+		PROPERTY_ENTRY_STRING("compatible", "test,shared-swnode"),
+		{ }
+	};
+	struct fwnode_handle *fwnode;
+	struct platform_device *pdev;
+	struct device *shared;
+	int ret;
+
+	pdev = platform_device_alloc(DEVICE_NAME, PLATFORM_DEVID_NONE);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	fwnode = fwnode_create_software_node(properties, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fwnode);
+	platform_device_set_fwnode(pdev, fwnode);
+
+	ret = platform_device_add(pdev);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	/*
+	 * A second, non-platform device referencing the same fwnode, like the
+	 * i2c adapter device created by i2c-designware.
+	 */
+	shared = kunit_kzalloc(test, sizeof(*shared), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, shared);
+
+	device_initialize(shared);
+	shared->release = platform_device_swnode_sharer_release;
+	ret = dev_set_name(shared, "test-swnode-sharer");
+	KUNIT_ASSERT_EQ(test, ret, 0);
+	device_set_node(shared, dev_fwnode(&pdev->dev));
+
+	ret = device_add(shared);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	device_unregister(shared);
+
+	/* The owner must still have its software node. */
+	KUNIT_EXPECT_PTR_EQ(test, dev_fwnode(&pdev->dev), fwnode);
+
+	platform_device_unregister(pdev);
+	fwnode_remove_software_node(fwnode);
+}
+
 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_swnode_shared),
 	KUNIT_CASE(platform_device_two_swnodes),
 	{}
 };
-- 
2.43.0

Re: [PATCH] driver core: platform: tests: add a shared software node test case

[Andy Shevchenko]

On Wed, Nov 04, 2026 at 08:24:16PM +0000, Stuart Summers wrote:
> Cover the pattern used by drm/xe + i2c-designware, where a software node
> assigned as a platform device's primary firmware node is handed to a
> second device via device_set_node(), and make sure removing that second
> device leaves the owner's node intact.
> 
> A potential fix for this issue in the drm/xe driver is being discussed
> in [1].
> 
> The signature in this case looks like this:
> Oops: general protection fault, probably for non-canonical address
> 0x6b6b6b6b6b6b6b73
> RIP: platform_device_release+0x6f/0x80

> Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> Assisted-by: LLM
> 
> [1]: https://patchwork.freedesktop.org/series/175858/

This is wrongly formatter tag block, also URL can be made a Link tag.
On top, Assisted-by is obsolete.

At the result it's expected to be

  Link: https://patchwork.freedesktop.org/series/175858/ [1]
  Signed-off-by: Stuart Summers <stuart.summers@intel.com>

And last, but not least — thanks for the test cases! It's always appreciated.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] driver core: platform: tests: add a shared software node test case

[Summers, Stuart]

On Thu, 2026-11-05 at 00:04 +0200, Andy Shevchenko wrote:
> On Wed, Nov 04, 2026 at 08:24:16PM +0000, Stuart Summers wrote:
> > Cover the pattern used by drm/xe + i2c-designware, where a software
> > node
> > assigned as a platform device's primary firmware node is handed to
> > a
> > second device via device_set_node(), and make sure removing that
> > second
> > device leaves the owner's node intact.
> > 
> > A potential fix for this issue in the drm/xe driver is being
> > discussed
> > in [1].
> > 
> > The signature in this case looks like this:
> > Oops: general protection fault, probably for non-canonical address
> > 0x6b6b6b6b6b6b6b73
> > RIP: platform_device_release+0x6f/0x80
> 
> > Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> > Assisted-by: LLM
> > 
> > [1]: https://patchwork.freedesktop.org/series/175858/
> 
> This is wrongly formatter tag block, also URL can be made a Link tag.
> On top, Assisted-by is obsolete.
> 
> At the result it's expected to be
> 
>   Link: https://patchwork.freedesktop.org/series/175858/ [1]
>   Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> 
> And last, but not least — thanks for the test cases! It's always
> appreciated.

Thanks for the review! And yeah makes sense, thanks. Let me fix that up
and resubmit.

Thanks,
Stuart

>