On Tue, Feb 02, 2021 at 04:02:16PM +0900, Masahiro Yamada wrote:
CONSOLE_LOGLEVEL_DEFAULT is nothing more than a shorthand of CONFIG_CONSOLE_LOGLEVEL_DEFAULT.
When you change CONFIG_CONSOLE_LOGLEVEL_DEFAULT from Kconfig, almost all objects are rebuilt because CONFIG_CONSOLE_LOGLEVEL_DEFAULT is used in <linux/printk.h>, which is included from most of source files.
In fact, there are only 4 users of CONSOLE_LOGLEVEL_DEFAULT:
arch/x86/platform/uv/uv_nmi.c drivers/firmware/efi/libstub/efi-stub-helper.c drivers/tty/sysrq.c kernel/printk/printk.c
So, when you change CONFIG_CONSOLE_LOGLEVEL_DEFAULT and rebuild the kernel, it is enough to recompile those 4 files.
Remove the CONSOLE_LOGLEVEL_DEFAULT definition from <linux/printk.h>, and use CONFIG_CONSOLE_LOGLEVEL_DEFAULT directly.
With this, the build system will rebuild the minimal number of objects.
Steps to confirm it:
[1] Do the full build [2] Change CONFIG_CONSOLE_LOGLEVEL_DEFAULT from 'make menuconfig' etc. [3] Rebuild
$ make SYNC include/config/auto.conf CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh DESCEND objtool CHK include/generated/compile.h CC kernel/printk/printk.o AR kernel/printk/built-in.a AR kernel/built-in.a CC drivers/tty/sysrq.o AR drivers/tty/built-in.a CC drivers/firmware/efi/libstub/efi-stub-helper.o STUBCPY drivers/firmware/efi/libstub/efi-stub-helper.stub.o AR drivers/firmware/efi/libstub/lib.a AR drivers/built-in.a GEN .version CHK include/generated/compile.h UPD include/generated/compile.h CC init/version.o AR init/built-in.a LD vmlinux.o ...
For the same reason, do likewise for CONSOLE_LOGLEVEL_QUIET and MESSAGE_LOGLEVEL_DEFAULT.
Signed-off-by: Masahiro Yamada masahiroy@kernel.org
arch/x86/platform/uv/uv_nmi.c | 2 +- drivers/firmware/efi/libstub/efi-stub-helper.c | 6 +++--- drivers/tty/sysrq.c | 4 ++-- drivers/video/fbdev/core/fbcon.c | 2 +- drivers/video/fbdev/efifb.c | 2 +- include/linux/printk.h | 10 ---------- init/main.c | 2 +- kernel/printk/printk.c | 6 +++--- 8 files changed, 12 insertions(+), 22 deletions(-)
Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org