[PATCH v3 0/3] drivers: base: Add tests showing devm handling inconsistencies

[Maxime Ripard <mripard@kernel.org>]

Hi,

This follows the discussion here:
https://lore.kernel.org/linux-kselftest/20230324123157.bbwvfq4gsxnlnfwb@houat/

This shows a couple of inconsistencies with regard to how device-managed
resources are cleaned up. Basically, devm resources will only be cleaned up
if the device is attached to a bus and bound to a driver. Failing any of
these cases, a call to device_unregister will not end up in the devm
resources being released.

We had to work around it in DRM to provide helpers to create a device for
kunit tests, but the current discussion around creating similar, generic,
helpers for kunit resumed interest in fixing this.

This can be tested using the command:
./tools/testing/kunit/kunit.py run --kunitconfig=drivers/base/test/

I added the fix David suggested back in that discussion which does fix
the tests. The SoB is missing, since David didn't provide it back then.

Let me know what you think,
Maxime

Signed-off-by: Maxime Ripard <mripard@kernel.org>
---
Changes in v3:
- Reworded the commit logs according to David's feedback
- Rebased on current next
- Link to v2: https://lore.kernel.org/r/20230329-kunit-devm-inconsistencies-test-v2-0-19feb71e864b@kernel.org

Changes in v2:
- Use an init function
- Document the tests
- Add a fix for the bugs
- Link to v1: https://lore.kernel.org/r/20230329-kunit-devm-inconsistencies-test-v1-0-c33127048375@cerno.tech

---
David Gow (1):
      drivers: base: Free devm resources when unregistering a device

Maxime Ripard (2):
      drivers: base: Add basic devm tests for root devices
      drivers: base: Add basic devm tests for platform devices

 drivers/base/core.c                      |  11 ++
 drivers/base/test/.kunitconfig           |   2 +
 drivers/base/test/Kconfig                |   4 +
 drivers/base/test/Makefile               |   3 +
 drivers/base/test/platform-device-test.c | 220 +++++++++++++++++++++++++++++++
 drivers/base/test/root-device-test.c     | 108 +++++++++++++++
 6 files changed, 348 insertions(+)
---
base-commit: c58c49dd89324b18a812762a2bfa5a0458e4f252
change-id: 20230329-kunit-devm-inconsistencies-test-5e5a7d01e60d

Best regards,
-- 
Maxime Ripard <mripard@kernel.org>