[PATCH v3] Documentation/kbuild: Document the kconfig choice default value

Robert Richter
2021-07-19T23:28:26Z

Document how choice defaults are determined:

Default of a choice is its first visible choice element unless it is
explicitly set by the 'default' property [1]. Choice elements do not
support default attributes. [2]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/symbol.c?h=v5.14-rc1#n245
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/kconfig/menu.c?h=v5.14-rc1#n494

Signed-off-by: Robert Richter <rrichter@amd.com>
---
v3: Fix base of v2 (rebased onto v5.14-rc2)
v2: clarification on 'default' attribute of a choice
added example
---
Documentation/kbuild/kconfig-language.rst | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
index 98c24183d8c3..d919dde0bcbf 100644
--- a/Documentation/kbuild/kconfig-language.rst
+++ b/Documentation/kbuild/kconfig-language.rst
@@ -417,6 +417,21 @@ definitions of that choice. If a [symbol] is associated to the choice,
then you may define the same choice (i.e. with the same entries) in another
place.

+The default value of a choice is set to the first visible choice
+element unless it is explicitly set by the 'default' property.
+
+Note:
+ Choice options do not support the 'default' attribute.
+
+E.g.::
+
+ choice
+ default C1
+ config C0
+ config C1
+ # no default attribute here
+ endchoice
+
comment::

"comment" <prompt>
--
2.29.2