Re: [PATCH v4 01/10] of: Add test managed wrappers for of_overlay_apply()/of_node_put()

On Tue, 23 Apr 2024 at 07:24, Stephen Boyd sboyd@kernel.org wrote:

Add test managed wrappers for of_overlay_apply() that automatically removes the overlay when the test is finished. This API is intended for use by KUnit tests that test code which relies on 'struct device_node's and of_*() APIs.

KUnit tests will call of_overlay_apply_kunit() to load an overlay that's been built into the kernel image. When the test is complete, the overlay will be removed.

This has a few benefits:

1. It keeps the tests hermetic because the overlay is removed when the test is complete. Tests won't even be aware that an overlay was loaded in another test.

2. The overlay code can live right next to the unit test that loads it. The overlay and the unit test can be compiled into one kernel module if desired.

3. We can test different device tree configurations by loading different overlays. The overlays can be written for a specific test, and there can be many of them loaded per-test without needing to jam all possible combinations into one DTB.

4. It also allows KUnit to test device tree dependent code on any architecture, not just UML. This allows KUnit tests to test architecture specific device tree code.

There are some potential pitfalls though. Test authors need to be careful to not overwrite properties in the live tree. The easiest way to do this is to add and remove nodes with a 'kunit-' prefix, almost guaranteeing that the same node won't be present in the tree loaded at boot.

Suggested-by: Rob Herring robh@kernel.org Cc: Rob Herring robh@kernel.org Cc: Saravana Kannan saravanak@google.com Signed-off-by: Stephen Boyd sboyd@kernel.org

---

This looks good to me. I'm not an expert on Device Tree Overlays, so can't guarantee it's perfect and/or the most ergonomic solution for any given use-case, but I definitely like the look of it from a KUnit point of view.

A few minor naming and config-related thoughts below, but otherwise:

Reviewed-by: David Gow davidgow@google.com

Cheers, -- David

Documentation/dev-tools/kunit/api/index.rst | 11 +++ Documentation/dev-tools/kunit/api/of.rst | 13 +++ drivers/of/Makefile | 1 + drivers/of/of_kunit.c | 99 +++++++++++++++++++++ include/kunit/of.h | 94 +++++++++++++++++++ 5 files changed, 218 insertions(+) create mode 100644 Documentation/dev-tools/kunit/api/of.rst create mode 100644 drivers/of/of_kunit.c create mode 100644 include/kunit/of.h

diff --git a/Documentation/dev-tools/kunit/api/index.rst b/Documentation/dev-tools/kunit/api/index.rst index 2d8f756aab56..282befa17edf 100644 --- a/Documentation/dev-tools/kunit/api/index.rst +++ b/Documentation/dev-tools/kunit/api/index.rst @@ -9,11 +9,15 @@ API Reference test resource functionredirection

•   of
  
  
  

This page documents the KUnit kernel testing API. It is divided into the following sections:

+Core KUnit API +==============

Documentation/dev-tools/kunit/api/test.rst

• Documents all of the standard testing API

@@ -25,3 +29,10 @@ Documentation/dev-tools/kunit/api/resource.rst Documentation/dev-tools/kunit/api/functionredirection.rst

• Documents the KUnit Function Redirection API

+Driver KUnit API +================

If we're adding a separate 'Driver' section here, it's probably sensible to move the existing device/driver helper documentation here, rather than leaving it in resource.rst as-is. I'm happy to do that in a follow-up patch, though.

+Documentation/dev-tools/kunit/api/of.rst

• • Documents the KUnit device tree (OF) API

diff --git a/Documentation/dev-tools/kunit/api/of.rst b/Documentation/dev-tools/kunit/api/of.rst new file mode 100644 index 000000000000..8587591c3e78 --- /dev/null +++ b/Documentation/dev-tools/kunit/api/of.rst @@ -0,0 +1,13 @@ +.. SPDX-License-Identifier: GPL-2.0

+==================== +Device Tree (OF) API +====================

+The KUnit device tree API is used to test device tree (of_*) dependent code.

+.. kernel-doc:: include/kunit/of.h

• :internal:

+.. kernel-doc:: drivers/of/of_kunit.c

• :export:

diff --git a/drivers/of/Makefile b/drivers/of/Makefile index 251d33532148..0dfd05079313 100644 --- a/drivers/of/Makefile +++ b/drivers/of/Makefile @@ -19,6 +19,7 @@ obj-y += kexec.o endif endif

+obj-$(CONFIG_KUNIT) += of_kunit.o

I'm tempted to have this either live in lib/kunit, or be behind a separate Kconfig option, particularly since this will end up as a separate module, as-is.

obj-$(CONFIG_OF_KUNIT_TEST) += of_test.o

obj-$(CONFIG_OF_UNITTEST) += unittest-data/ diff --git a/drivers/of/of_kunit.c b/drivers/of/of_kunit.c new file mode 100644 index 000000000000..f63527268a51 --- /dev/null +++ b/drivers/of/of_kunit.c @@ -0,0 +1,99 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Test managed device tree APIs
• */

+#include <linux/of.h> +#include <linux/of_fdt.h>

+#include <kunit/of.h> +#include <kunit/test.h> +#include <kunit/resource.h>

+static void of_overlay_fdt_apply_kunit_exit(void *ovcs_id) +{

•   of_overlay_remove(ovcs_id);
  

+}

+/**

• • of_overlay_fdt_apply_kunit() - Test managed of_overlay_fdt_apply()
• • @test: test context
• • @overlay_fdt: device tree overlay to apply
• • @overlay_fdt_size: size in bytes of @overlay_fdt
• • @ovcs_id: identifier of overlay, used to remove the overlay
• • Just like of_overlay_fdt_apply(), except the overlay is managed by the test
• • case and is automatically removed with of_overlay_remove() after the test
• • case concludes.
• • Return: 0 on success, negative errno on failure
• */

+int of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,

•                          u32 overlay_fdt_size, int *ovcs_id)
  

We're using kunit_ as a prefix for the device helpers (e.g. kunit_device_register()), so it may make sense to do that here, too. It's not as important as with the platform_device helpers, which are very similar to the existing device ones, but if we want to treat these as "part of KUnit which deals with of_overlays", rather than "part of "of_overlay which deals with KUnit", this may fit better.

Thoughts?

+{

•   int ret;
  

•   int *copy_id;
  

•   if (!IS_ENABLED(CONFIG_OF_OVERLAY))
  

•           kunit_skip(test, "requires CONFIG_OF_OVERLAY");
  

•   if (!IS_ENABLED(CONFIG_OF_EARLY_FLATTREE))
  

•           kunit_skip(test, "requires CONFIG_OF_EARLY_FLATTREE for root node");
  

•   copy_id = kunit_kmalloc(test, sizeof(*copy_id), GFP_KERNEL);
  

•   if (!copy_id)
  

•           return -ENOMEM;
  

•   ret = of_overlay_fdt_apply(overlay_fdt, overlay_fdt_size,
  

•                              ovcs_id, NULL);
  

•   if (ret)
  

•           return ret;
  

•   *copy_id = *ovcs_id;
  

•   return kunit_add_action_or_reset(test, of_overlay_fdt_apply_kunit_exit,
  

•                                    copy_id);
  

+} +EXPORT_SYMBOL_GPL(of_overlay_fdt_apply_kunit);

+/**

• • __of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() variant
• • @test: test context
• • @overlay_begin: start address of overlay to apply
• • @overlay_end: end address of overlay to apply
• • This is mostly internal API. See of_overlay_apply_kunit() for the wrapper
• • that makes this easier to use.
• • Similar to of_overlay_fdt_apply(), except the overlay is managed by the test
• • case and is automatically removed with of_overlay_remove() after the test
• • case concludes.
• • Return: 0 on success, negative errno on failure
• */

+int __of_overlay_apply_kunit(struct kunit *test, u8 *overlay_begin,

•                        const u8 *overlay_end)
  

+{

•   int unused;
  

•   return of_overlay_fdt_apply_kunit(test, overlay_begin,
  

•                                     overlay_end - overlay_begin,
  

•                                     &unused);
  

+} +EXPORT_SYMBOL_GPL(__of_overlay_apply_kunit);

+/**

• • of_node_put_kunit() - Test managed of_node_put()
• • @test: test context
• • @node: node to pass to `of_node_put()`
• • Just like of_node_put(), except the node is managed by the test case and is
• • automatically put with of_node_put() after the test case concludes.
• */

+void of_node_put_kunit(struct kunit *test, struct device_node *node) +{

•   if (kunit_add_action(test, (kunit_action_t *)&of_node_put, node)) {
  

•           KUNIT_FAIL(test,
  

•                      "Can't allocate a kunit resource to put of_node\n");
  

•   }
  

+} +EXPORT_SYMBOL_GPL(of_node_put_kunit); diff --git a/include/kunit/of.h b/include/kunit/of.h new file mode 100644 index 000000000000..9981442ba578 --- /dev/null +++ b/include/kunit/of.h @@ -0,0 +1,94 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _KUNIT_OF_H +#define _KUNIT_OF_H

+#include <kunit/test.h>

+struct device_node;

+#ifdef CONFIG_OF

Do we also need to check for CONFIG_OF_OVERLAY here?

Also, how useful is it to compile but skip tests without CONFIG_OF{,_OVERLAY} enabled? The other option is a compile error, which may make it more obvious that these are disabled if it's unexpected.

Thoughts?

+int of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,

•                          u32 overlay_fdt_size, int *ovcs_id);
  

+int __of_overlay_apply_kunit(struct kunit *test, u8 *overlay_begin,

•                        const u8 *overlay_end);
  

+void of_node_put_kunit(struct kunit *test, struct device_node *node);

+#else

+static inline int +of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,

•                      u32 overlay_fdt_size, int *ovcs_id)
  

+{

•   kunit_skip(test, "requires CONFIG_OF");
  

•   return -EINVAL;
  

+}

+static inline int +__of_overlay_apply_kunit(struct kunit *test, u8 *overlay_begin,

•                    const u8 *overlay_end)
  

+{

•   kunit_skip(test, "requires CONFIG_OF");
  

•   return -EINVAL;
  

+}

+static inline +void of_node_put_kunit(struct kunit *test, struct device_node *node) +{

•   kunit_skip(test, "requires CONFIG_OF");
  

+}

+#endif /* !CONFIG_OF */

+/**

• • of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() for built-in overlays
• • @test: test context
• • @overlay_name: name of overlay to apply
• • This macro is used to apply a device tree overlay built with the
• • cmd_dt_S_dtbo rule in scripts/Makefile.lib that has been compiled into the
• • kernel image or KUnit test module. The overlay is automatically removed when
• • the test is finished.
• • Unit tests that need device tree nodes should compile an overlay file with
• • @overlay_name.dtbo.o in their Makefile along with their unit test and then
• • load the overlay during their test. The @overlay_name matches the filename
• • of the overlay without the dtbo filename extension. If CONFIG_OF_OVERLAY is
• • not enabled, the @test will be skipped.
• • In the Makefile
• • .. code-block:: none

• • obj-$(CONFIG_OF_OVERLAY_KUNIT_TEST) += overlay_test.o kunit_overlay_test.dtbo.o
    

• • In the test
• • .. code-block:: c

• • static void of_overlay_kunit_of_overlay_apply(struct kunit *test)
    

• • {
    

• •         struct device_node *np;
    

• •         KUNIT_ASSERT_EQ(test, 0,
    

• •                         of_overlay_apply_kunit(test, kunit_overlay_test));
    

• •         np = of_find_node_by_name(NULL, "test-kunit");
    

• •         KUNIT_EXPECT_NOT_ERR_OR_NULL(test, np);
    

• •         of_node_put(np);
    

• • }
    

• • Return: 0 on success, negative errno on failure.
• */

+#define of_overlay_apply_kunit(test, overlay_name) \ +({ \

•   extern uint8_t __dtbo_##overlay_name##_begin[];         \
  

•   extern uint8_t __dtbo_##overlay_name##_end[];           \
  

•                                                           \
  

•   __of_overlay_apply_kunit((test),                        \
  

•                   __dtbo_##overlay_name##_begin,          \
  

•                   __dtbo_##overlay_name##_end);           \
  

+})

+#endif

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