Enabling a (modular) test must not silently enable additional kernel
functionality, as that may increase the attack vector of a product.

Fix this by:
  1. making REGMAP visible if CONFIG_KUNIT_ALL_TESTS is enabled,
  2. making REGMAP_KUNIT depend on REGMAP instead of selecting it.

After this, one can safely enable CONFIG_KUNIT_ALL_TESTS=m to build
modules for all appropriate tests for ones system, without pulling in
extra unwanted functionality, while still allowing a tester to manually
enable REGMAP and its test suite on a system where REGMAP is not enabled
by default.

Fixes: 2238959b6ad27040 ("regmap: Add some basic kunit tests")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
v2:
  - Make REGMAP visible if CONFIG_KUNIT_ALL_TESTS is enabled.
---
 drivers/base/regmap/Kconfig | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
index 33a8366e22a584a5..0db2021f7477f2ab 100644
--- a/drivers/base/regmap/Kconfig
+++ b/drivers/base/regmap/Kconfig
@@ -4,16 +4,23 @@
 # subsystems should select the appropriate symbols.
 
 config REGMAP
+	bool "Register Map support" if KUNIT_ALL_TESTS
 	default y if (REGMAP_I2C || REGMAP_SPI || REGMAP_SPMI || REGMAP_W1 || REGMAP_AC97 || REGMAP_MMIO || REGMAP_IRQ || REGMAP_SOUNDWIRE || REGMAP_SOUNDWIRE_MBQ || REGMAP_SCCB || REGMAP_I3C || REGMAP_SPI_AVMM || REGMAP_MDIO || REGMAP_FSI)
 	select IRQ_DOMAIN if REGMAP_IRQ
 	select MDIO_BUS if REGMAP_MDIO
-	bool
+	help
+	  Enable support for the Register Map (regmap) access API.
+
+	  Usually, this option is automatically selected when needed.
+	  However, you may want to enable it manually for running the regmap
+	  KUnit tests.
+
+	  If unsure, say N.
 
 config REGMAP_KUNIT
 	tristate "KUnit tests for regmap"
-	depends on KUNIT
+	depends on KUNIT && REGMAP
 	default KUNIT_ALL_TESTS
-	select REGMAP
 	select REGMAP_RAM
 
 config REGMAP_AC97
-- 
2.34.1

On Wed, 26 Apr 2023 15:35:45 +0200, Geert Uytterhoeven wrote:
> Enabling a (modular) test must not silently enable additional kernel
> functionality, as that may increase the attack vector of a product.
> 
> Fix this by:
>   1. making REGMAP visible if CONFIG_KUNIT_ALL_TESTS is enabled,
>   2. making REGMAP_KUNIT depend on REGMAP instead of selecting it.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git for-next

Thanks!

[1/1] regmap: REGMAP_KUNIT must not select REGMAP
      commit: 70a640c0efa7667453c3911b13335304ce46ad8b

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark