Hi Sam, Geert, On Fri, May 10, 2019 at 4:04 PM Sam Ravnborg <sam@xxxxxxxxxxxx> wrote: > > Hi Geert/Masahiro. > > On Fri, May 10, 2019 at 08:46:35AM +0200, Geert Uytterhoeven wrote: > > Hi Yamada-san, > > > > On Fri, May 10, 2019 at 8:14 AM Masahiro Yamada > > <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > > Kconfig updates the .config when it exits even if its content is > > > exactly the same as before. Since its timestamp becomes newer than > > > that of other build artifacts, additional processing is invoked, > > > which is annoying. > > > > > > - syncconfig is invoked to update include/config/auto.conf, etc. > > > > > > - kernel/config.o is recompiled if CONFIG_IKCONFIG is enabled, > > > then vmlinux is relinked as well. > > > > > > If the .config is not changed at all, we do not have to even > > > touch it. Just bail out showing "No change to .config". > It would be preferable that if nothing changed no output is generated. > Like we do not tell that we did not build a .o file because the .c file > had not changed. > Less noise for a kernel build where nothings happens. > > > This causes a semantic change for the meaning of ".config.old", which is > > no longer updated if .config has not changed. > > Hence its contents may no longer correspond to the previous config, but to > > an arbitrary older version. > This semantic change is good. > So we now have a .config.old that correspond to the state before > the last change. Also after several kernel builds. I agree. When there is no change in the configuration, Kconfig will not even attempt to output anything. Updating only .config.old is strange. Thanks. -- Best Regards Masahiro Yamada
