[PATCH 1/3] kconfig: Add "def_string", "def_int" and "def_hex"
From: Kees Cook
Date: Fri Sep 18 2026 - 21:00:45 EST
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@xxxxxxxxxxxxx/ [1]
Assisted-by: LLM
Signed-off-by: Kees Cook <kees@xxxxxxxxxx>
---
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nicolas Schier <nsc@xxxxxxxxxx>
Cc: Julian Braha <julianbraha@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Nicolas Pitre <nico@xxxxxxxxxxx>
Cc: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Andrew Jones <andrew.jones@xxxxxxxxx>
Cc: <linux-kbuild@xxxxxxxxxxxxxxx>
Cc: <linux-doc@xxxxxxxxxxxxxxx>
---
scripts/kconfig/tests/def_type/Kconfig | 28 +++++++++++++++++++
scripts/kconfig/tests/def_type/guard_n.config | 1 +
scripts/kconfig/tests/def_type/guard_y.config | 1 +
scripts/kconfig/tests/def_type/__init__.py | 18 ++++++++++++
.../kconfig/tests/def_type/expected_guard_n | 9 ++++++
.../kconfig/tests/def_type/expected_guard_y | 11 ++++++++
scripts/kconfig/kconfig-sym-check.pl | 2 +-
scripts/kconfig/lexer.l | 3 ++
scripts/kconfig/parser.y | 6 ++++
Documentation/kbuild/kconfig-language.rst | 13 ++++++++-
10 files changed, 90 insertions(+), 2 deletions(-)
create mode 100644 scripts/kconfig/tests/def_type/Kconfig
create mode 100644 scripts/kconfig/tests/def_type/guard_n.config
create mode 100644 scripts/kconfig/tests/def_type/guard_y.config
create mode 100644 scripts/kconfig/tests/def_type/__init__.py
create mode 100644 scripts/kconfig/tests/def_type/expected_guard_n
create mode 100644 scripts/kconfig/tests/def_type/expected_guard_y
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/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
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/kconfig-sym-check.pl b/scripts/kconfig/kconfig-sym-check.pl
index daa5285fdefc..c8dd07f8b27c 100755
--- a/scripts/kconfig/kconfig-sym-check.pl
+++ b/scripts/kconfig/kconfig-sym-check.pl
@@ -90,7 +90,7 @@ foreach my $file (@files) {
next;
}
- if (/^\s*(default|def_bool|def_tristate|select|depends\s+on|imply|visible\s+if|range|if|bool|tristate|int|hex|string|prompt)\s+(.+)\s*$/) {
+ if (/^\s*(default|def_bool|def_tristate|def_string|def_int|def_hex|select|depends\s+on|imply|visible\s+if|range|if|bool|tristate|int|hex|string|prompt)\s+(.+)\s*$/) {
my $s = $2;
$s =~ s/"(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*'//g;
$s =~ s/#.*//;
diff --git a/scripts/kconfig/lexer.l b/scripts/kconfig/lexer.l
index a6155422b4a6..1fa521199d4a 100644
--- a/scripts/kconfig/lexer.l
+++ b/scripts/kconfig/lexer.l
@@ -105,6 +105,9 @@ n [A-Za-z0-9_-]
"comment" return T_COMMENT;
"config" return T_CONFIG;
"def_bool" return T_DEF_BOOL;
+"def_hex" return T_DEF_HEX;
+"def_int" return T_DEF_INT;
+"def_string" return T_DEF_STRING;
"def_tristate" return T_DEF_TRISTATE;
"default" return T_DEFAULT;
"depends" return T_DEPENDS;
diff --git a/scripts/kconfig/parser.y b/scripts/kconfig/parser.y
index 5fb6f07b6ad2..2174baf2b3fd 100644
--- a/scripts/kconfig/parser.y
+++ b/scripts/kconfig/parser.y
@@ -53,6 +53,9 @@ struct menu *current_menu, *current_entry, *current_choice;
%token T_CONFIG
%token T_DEFAULT
%token T_DEF_BOOL
+%token T_DEF_HEX
+%token T_DEF_INT
+%token T_DEF_STRING
%token T_DEF_TRISTATE
%token T_DEPENDS
%token T_ENDCHOICE
@@ -309,6 +312,9 @@ type:
default:
T_DEFAULT { $$ = S_UNKNOWN; }
| T_DEF_BOOL { $$ = S_BOOLEAN; }
+ | T_DEF_HEX { $$ = S_HEX; }
+ | T_DEF_INT { $$ = S_INT; }
+ | T_DEF_STRING { $$ = S_STRING; }
| T_DEF_TRISTATE { $$ = S_TRISTATE; }
/* if entry */
diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
index d9338407c1c6..00402d43e0dc 100644
--- a/Documentation/kbuild/kconfig-language.rst
+++ b/Documentation/kbuild/kconfig-language.rst
@@ -113,11 +113,22 @@ applicable everywhere (see syntax).
- type definition + default value::
- "def_bool"/"def_tristate" <expr> ["if" <expr>]
+ "def_bool" <expr> ["if" <expr>]
+ "def_tristate" <expr> ["if" <expr>]
+ "def_string" <expr> ["if" <expr>]
+ "def_int" <expr> ["if" <expr>]
+ "def_hex" <expr> ["if" <expr>]
This is a shorthand notation for a type definition plus a value.
Optionally dependencies for this default value can be added with "if".
+ The shorthand supplies the type once, and is otherwise an ordinary
+ default: it is the first entry of the list described above, so any
+ further "default" entries still apply when its "if" is not met. Since
+ that leaves the type definition inside one arm of a list, spelling the
+ type out on its own line reads better for a symbol with several
+ defaults.
+
- dependencies: "depends on" <expr> ["if" <expr>]
This defines a dependency for this menu entry. If multiple
--
2.34.1