kconfig: refactor choice value calculation
Handling choices has always been in a PITA in Kconfig.
For example, fixes and reverts were repeated for randconfig with
KCONFIG_ALLCONFIG:
- 422c809f03f0 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG")
- 23a5dfdad22a ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"")
- 8357b48549e1 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG")
- 490f16171119 ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"")
As these commits pointed out, randconfig does not randomize choices when
KCONFIG_ALLCONFIG is used. This issue still remains.
[Test Case]
choice
prompt "choose"
config A
bool "A"
config B
bool "B"
endchoice
$ echo > all.config
$ make KCONFIG_ALLCONFIG=1 randconfig
The output is always as follows:
CONFIG_A=y
# CONFIG_B is not set
Not only randconfig, but other all*config variants are also broken with
KCONFIG_ALLCONFIG.
With the same Kconfig,
$ echo '# CONFIG_A is not set' > all.config
$ make KCONFIG_ALLCONFIG=1 allyesconfig
You will get this:
CONFIG_A=y
# CONFIG_B is not set
This is incorrect because it does not respect all.config.
The correct output should be:
# CONFIG_A is not set
CONFIG_B=y
To handle user inputs more accurately, this commit refactors the code
based on the following principles:
- When a user value is given, Kconfig must set it immediately.
Do not defer it by setting SYMBOL_NEED_SET_CHOICE_VALUES.
- The SYMBOL_DEF_USER flag must not be cleared, unless a new config
file is loaded. Kconfig must not forget user inputs.
In addition, user values for choices must be managed with priority.
If user inputs conflict within a choice block, the newest value wins.
The values given by randconfig have lower priority than explicit user
inputs.
This commit implements it by using a linked list. Every time a choice
block gets a new input, it is moved to the top of the list.
Let me explain how it works.
Let's say, we have a choice block that consists of five symbols:
A, B, C, D, and E.
Initially, the linked list looks like this:
A(=?) --> B(=?) --> C(=?) --> D(=?) --> E(=?)
Suppose randconfig is executed with the following KCONFIG_ALLCONFIG:
CONFIG_C=y
# CONFIG_A is not set
CONFIG_D=y
First, CONFIG_C=y is read. C is set to 'y' and moved to the top.
C(=y) --> A(=?) --> B(=?) --> D(=?) --> E(=?)
Next, '# CONFIG_A is not set' is read. A is set to 'n' and moved to
the top.
A(=n) --> C(=y) --> B(=?) --> D(=?) --> E(=?)
Then, 'CONFIG_D=y' is read. D is set to 'y' and moved to the top.
D(=y) --> A(=n) --> C(=y) --> B(=?) --> E(=?)
Lastly, randconfig shuffles the order of the remaining symbols,
resulting in:
D(=y) --> A(=n) --> C(=y) --> B(=y) --> E(=y)
or
D(=y) --> A(=n) --> C(=y) --> E(=y) --> B(=y)
When calculating the output, the linked list is traversed and the first
visible symbol with 'y' is taken. In this case, it is D if visible.
If D is hidden by 'depends on', the next node, A, is examined. Since
it is already specified as 'n', it is skipped. Next, C is checked, and
selected if it is visible.
If C is also invisible, either B or E is chosen as a result of the
randomization.
If B and E are also invisible, the linked list is traversed in the
reverse order, and the least prioritized 'n' symbol is chosen. It is
A in this case.
Now, Kconfig remembers all user values. This is a big difference from
the previous implementation, where Kconfig would forget CONFIG_C=y when
CONFIG_D=y appeared in the same input file.
The new appaorch respects user-specified values as much as possible.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
7 files changed
