On Thu, Dec 6, 2012 at 1:07 AM, Ulf Magnusson <ulfalizer.lkml2@xxxxxxxxx> wrote: > Hi, > > Consider the following Kconfig file: > > config MODULES > def_bool y > > choice > tristate "C1" > config A > tristate "A" > config B > tristate "B" > endchoice > > choice > bool "C2" if A > config C > bool "C" > config D > bool "D" > endchoice > > When this Kconfig file is used with a configuration file containing > just "CONFIG_A=y", conf generates the following invalid configuration: > > CONFIG_MODULES=y > CONFIG_A=m > # CONFIG_B is not set > CONFIG_C=y > # CONFIG_D is not set > > mconf on the other hand generates the correct configuration: > > CONFIG_MODULES=y > CONFIG_A=y > # CONFIG_B is not set > CONFIG_C=y > # CONFIG_D is not set > > To see this, compare the .config files generated by the following commands: > > $ scripts/kconfig/conf --defconfig=bug_config bug_Kconfig > > $ cp bug_config .config > $ scripts/kconfig/mconf bug_Kconfig > > The root cause of the problem is the sym_calc_value(csym) call at the > end of conf_set_all_new_symbols(). Since the second 'choice' depends > on A, that call causes the value of A to be calculated. But this also > causes SYMBOL_VALID to be set on A, preventing it from being > reevaluated later when the configuration is written in conf_write(). > This reevaluation is required to get the correct value since only by > then will the choice have SYMBOL_DEF_USER set on it (set in > set_all_choice_values()). > > Some possible fixes: > (1) Add another sym_clear_all_valid() call at the end of > conf_set_all_new_symbols(). This is kinda wasteful. > (2) Just randomize_choice_values() seems to actually need the > sym_calc_value(csym). It could probably be moved into that function, > perhaps doing the additional sym_clear_all_valid() there unless > there's something neater you could do. > > It would probably be safer if someone more familiar with the > randomization stuff wrote the actual patch. > > Linux version is 3.7.0-rc4, though this bug has likely been around a while. > > /Ulf This bug causes an incorrect configuration to be generated for Blackfin with the following defconfigs by the way: CM-BF537U_defconfig BF548-EZKIT_defconfig BF527-EZKIT_defconfig BF527-EZKIT-V2_defconfig TCM-BF537_defconfig For example: $ make ARCH=blackfin CM-BF537U_defconfig $ cp .config ._config $ cp arch/blackfin/configs/CM-BF537U_defconfig .config $ make ARCH=blackfin menuconfig *save and exit* $ diff -u .config ._config --- .config 2012-12-08 08:46:07.598588422 +0100 +++ ._config 2012-12-08 08:44:03.566584623 +0100 @@ -997,9 +997,9 @@ # CONFIG_USB_MV_UDC is not set # CONFIG_USB_M66592 is not set # CONFIG_USB_NET2272 is not set -CONFIG_USB_LIBCOMPOSITE=y +CONFIG_USB_LIBCOMPOSITE=m # CONFIG_USB_ZERO is not set -CONFIG_USB_ETH=y +CONFIG_USB_ETH=m CONFIG_USB_ETH_RNDIS=y # CONFIG_USB_ETH_EEM is not set # CONFIG_USB_G_NCM is not set The defconfig itself contains "CONFIG_USB_ETH=y", which 'conf' incorrectly truncates. I noticed the bug because it causes the only test suite failures in Kconfiglib (https://github.com/ulfalizer/Kconfiglib) with Linus' latest kernel, in the tests that compare output between Kconfiglib and the scripts/kconfig/*conf utilities. (I'm in the process of updating Kconfiglib. I have no intention to get it into the kernel - just a handy tool.) /Ulf -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
