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When a prompt is followed by "if <expr>", the symbol is configurable
when the if-conditional evaluates to true.
A typical usage is as follows:
menuconfig BLOCK
bool "Enable the block layer" if EXPERT
default y
When EXPERT=n, the prompt is hidden, but this config entry is still
active, and BLOCK is set to its default value 'y'. When EXPERT=y, the
prompt is shown, making BLOCK a user-configurable option.
This usage is common throughout the kernel tree, but it has never worked
within a choice block.
[Test Code]
config EXPERT
bool "Allow expert users to modify more options"
choice
prompt "Choose" if EXPERT
config A
bool "A"
config B
bool "B"
endchoice
[Result]
# CONFIG_EXPERT is not set
When the prompt is hidden, the choice block should produce the default
without asking for the user's preference. Hence, the output should be:
# CONFIG_EXPERT is not set
CONFIG_A=y
# CONFIG_B is not set
Removing unnecessary hacks fixes the issue.
This commit also changes the behavior of 'select' by choice members.
[Test Code 2]
config MODULES
def_bool y
modules
config DEP
def_tristate m
if DEP
choice
prompt "choose"
config A
bool "A"
select C
endchoice
config B
def_bool y
select D
endif
config C
tristate
config D
tristate
The current output is as follows:
CONFIG_MODULES=y
CONFIG_DEP=m
CONFIG_A=y
CONFIG_B=y
CONFIG_C=y
CONFIG_D=m
With this commit, the output will be changed as follows:
CONFIG_MODULES=y
CONFIG_DEP=m
CONFIG_A=y
CONFIG_B=y
CONFIG_C=m
CONFIG_D=m
CONFIG_C will be changed to 'm' because 'select C' will inherit the
dependency on DEP, which is 'm'.
This change is aligned with the behavior of 'select' outside a choice
block; 'select D' depends on DEP, therefore D is selected by (B && DEP).
Note:
With this commit, allmodconfig will set CONFIG_USB_ROLE_SWITCH to 'm'
instead of 'y'. I did not see any build regression with this change.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.