A root node is required to apply DT overlays. A root node is usually
present after commit 7b937cc243 ("of: Create of_root if no dtb
provided by firmware"), except for on arm64 systems booted with ACPI
tables. In that case, the root node is intentionally not populated
because it would "allow DT devices to be instantiated atop an ACPI base
system"[1].
Introduce an OF function that skips the kunit test if the root node
isn't populated. Limit the test to when both CONFIG_ARM64 and
CONFIG_ACPI are set, because otherwise the lack of a root node is a bug.
Make the function private and take a kunit test parameter so that it
can't be abused to test for the presence of the root node in non-test
code.
Use this function to skip tests that require the root node. Currently
that's the DT tests and any tests that apply overlays.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/r/6cd337fb-38f0-41cb-b942-5844b84433db@roeck-us.net
Link: https://lore.kernel.org/r/Zd4dQpHO7em1ji67@FVFF77S0Q05N.cambridge.arm.com [1]
Fixes: 893ecc6d2d ("of: Add KUnit test to confirm DTB is loaded")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20241009204133.1169931-1-sboyd@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
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>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20240718210513.3801024-3-sboyd@kernel.org
