kconfig: Add "def_string", "def_int" and "def_hex"

Kconfig has offered "def_bool" and "def_tristate" as a shorthand for a
type definition plus a default since before the git era, but has never
offered the equivalent for the other three types. Conor Dooley ran into
this gap[1] when fixing a symbol that had been given the wrong type:

  Unfortunately, there is no such thing as "def_string", but in this
  case we can use "default" to propagate the value of ...

Nothing in the grammar requires the restriction. The rule that consumes
a default is already type agnostic. Add the three missing types. No
changes are needed to existing diagnostics. E.g. declaring a symbol
"bool" and then assigning it with "def_string" still reports

  warning: ignoring type redefinition of 'CONFLICT' from 'bool' to 'string'

Added tests for the types.

Build tested ARCH=x86_64 with GCC 16.2.0. Tests pass with "make testconfig".

Link: https://lore.kernel.org/all/20230111104848.2088516-1-conor.dooley@microchip.com/ [1]
Assisted-by: LLM
Signed-off-by: Kees Cook <kees@kernel.org>
Tested-by: Julian Braha <julianbraha@gmail.com>
Reviewed-by: Julian Braha <julianbraha@gmail.com>
Link: https://patch.msgid.link/20260919005929.4077729-1-kees@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

6 files changed, 68 insertions, 0 deletions

diff --git a/scripts/kconfig/tests/def_type/Kconfig b/scripts/kconfig/tests/def_type/Kconfig
new file mode 100644
index 000000000000..fbee37a63179
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/Kconfig
@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: GPL-2.0
+# The def_<type> shorthands: a type definition plus a default value.
+
+config MODULES
+	bool "Enable loadable module support"
+	modules
+	default y
+
+config GUARD
+	bool "Guard symbol"
+
+config DEF_BOOL
+	def_bool GUARD
+
+config DEF_TRISTATE
+	def_tristate m if GUARD
+
+config DEF_STRING
+	def_string "guarded" if GUARD
+	default "fallback"
+
+config DEF_INT
+	def_int 64 if GUARD
+	default 32
+
+config DEF_HEX
+	def_hex 0xdead if GUARD
+	default 0x0
diff --git a/scripts/kconfig/tests/def_type/__init__.py b/scripts/kconfig/tests/def_type/__init__.py
new file mode 100644
index 000000000000..1ebaf5da07c8
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/__init__.py
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+"""
+Set a symbol's type and its default value in one line.
+
+"def_bool", "def_tristate", "def_string", "def_int" and "def_hex" are
+shorthand for a type definition plus a "default" property.  Check that
+each one sets the type, and that an "if" on the shorthand does not
+disturb the usual default cascade: the shorthand is only the first arm
+of the list, so a later "default" still applies when its condition is
+not met.
+"""
+
+def test(conf):
+    assert conf.olddefconfig(dot_config='guard_y.config') == 0
+    assert conf.config_matches('expected_guard_y')
+
+    assert conf.olddefconfig(dot_config='guard_n.config') == 0
+    assert conf.config_matches('expected_guard_n')
diff --git a/scripts/kconfig/tests/def_type/expected_guard_n b/scripts/kconfig/tests/def_type/expected_guard_n
new file mode 100644
index 000000000000..14719720a8b9
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/expected_guard_n
@@ -0,0 +1,9 @@
+#
+# Automatically generated file; DO NOT EDIT.
+# Main menu
+#
+CONFIG_MODULES=y
+# CONFIG_GUARD is not set
+CONFIG_DEF_STRING="fallback"
+CONFIG_DEF_INT=32
+CONFIG_DEF_HEX=0x0
diff --git a/scripts/kconfig/tests/def_type/expected_guard_y b/scripts/kconfig/tests/def_type/expected_guard_y
new file mode 100644
index 000000000000..b2844072d0b8
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/expected_guard_y
@@ -0,0 +1,11 @@
+#
+# Automatically generated file; DO NOT EDIT.
+# Main menu
+#
+CONFIG_MODULES=y
+CONFIG_GUARD=y
+CONFIG_DEF_BOOL=y
+CONFIG_DEF_TRISTATE=m
+CONFIG_DEF_STRING="guarded"
+CONFIG_DEF_INT=64
+CONFIG_DEF_HEX=0xdead
diff --git a/scripts/kconfig/tests/def_type/guard_n.config b/scripts/kconfig/tests/def_type/guard_n.config
new file mode 100644
index 000000000000..ed9ad6c1a2d4
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/guard_n.config
@@ -0,0 +1 @@
+# CONFIG_GUARD is not set
diff --git a/scripts/kconfig/tests/def_type/guard_y.config b/scripts/kconfig/tests/def_type/guard_y.config
new file mode 100644
index 000000000000..afe35b084542
--- /dev/null
+++ b/scripts/kconfig/tests/def_type/guard_y.config
@@ -0,0 +1 @@
+CONFIG_GUARD=y