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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: - 422c809f ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG") - 23a5dfda ("Revert "kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG"") - 8357b485 ("kconfig: fix randomising choice entries in presence of KCONFIG_ALLCONFIG") - 490f1617 ("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>