[RFC PATCH v3 6/6] char: mem: add Kconfig option for devmem KUnit tests

[Gabriele Paoloni <gpaoloni@redhat.com>]

From: Alessandro Carminati <acarmina@redhat.com>

Introduce a dedicated Kconfig option to enable extended KUnit testing
for /dev/mem behavior.

The option enables tests covering I/O memory access restrictions,
including behavior under CONFIG_IO_STRICT_DEVMEM. Because the tests may
perform reads from I/O regions, they are opt-in and documented with
appropriate warnings.

This keeps test coverage explicit and avoids unintended hardware
side effects.

Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
---
 drivers/char/Kconfig  | 21 +++++++++++++++++++++
 drivers/char/Makefile |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index d2cfc584e202..cd3e47b47f44 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -317,6 +317,27 @@ config DEVMEM
 	  memory.
 	  When in doubt, say "Y".
 
+config DEVMEM_KUNIT_TEST
+	tristate "KUnit tests for /dev/mem" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  Enables in-kernel unit tests for /dev/mem read/write logic.
+
+config DEVMEM_KUNIT_TEST_IO
+	bool "KUnit tests for /dev/mem extended to I/O space"
+	depends on DEVMEM_KUNIT_TEST
+	default n
+	help
+	  Extend KUnit tests for devmem to cover IO space.
+	  When CONFIG_IO_STRICT_DEVMEM is enabled, the kernel denies
+	  access to claimed IO regions. Enabling this option adds two
+	  KUnit test cases to verify this behavior.
+	  Note: These tests perform read operations, which can have
+	  side effects on certain hardware.
+	  Enable this only if you are certain your hardware handles
+	  unsolicited reads safely.
+
 config NVRAM
 	tristate "/dev/nvram support"
 	depends on X86 || HAVE_ARCH_NVRAM_OPS
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 1291369b9126..176f2b8f98dc 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -4,6 +4,7 @@
 #
 
 obj-y				+= mem.o random.o
+obj-$(CONFIG_DEVMEM_KUNIT_TEST)	+= mem_kunit_test.o
 obj-$(CONFIG_TTY_PRINTK)	+= ttyprintk.o
 obj-y				+= misc.o
 obj-$(CONFIG_TEST_MISC_MINOR)	+= misc_minor_kunit.o
-- 
2.48.1