[PATCH v2] regmap: REGMAP_KUNIT must not select REGMAP

[Geert Uytterhoeven <geert@linux-m68k.org>]

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