From: Randy Dunlap <randy.dunlap@xxxxxxxxxx> I'm trying to clean up some of the Documentation diretory. What do you think about this one? Move smart-config.txt to Documentation/kbuild/ since it is build/config-related. Signed-off-by: Randy Dunlap <randy.dunlap@xxxxxxxxxx> --- Documentation/kbuild/smart-config.txt | 98 ++++++++++++++++++++++++ Documentation/smart-config.txt | 98 ------------------------ 2 files changed, 98 insertions(+), 98 deletions(-) --- /dev/null +++ linux-2.6.25-rc3-git4/Documentation/kbuild/smart-config.txt @@ -0,0 +1,98 @@ +Smart CONFIG_* Dependencies +1 August 1999 + +Michael Chastain <mec@xxxxxxxxx> +Werner Almesberger <almesber@xxxxxxxxxxxxxx> +Martin von Loewis <martin@xxxxxxxxxxxxxxxxxxxxxxxxx> + +Here is the problem: + + Suppose that drivers/net/foo.c has the following lines: + + #include <linux/config.h> + + ... + + #ifdef CONFIG_FOO_AUTOFROB + /* Code for auto-frobbing */ + #else + /* Manual frobbing only */ + #endif + + ... + + #ifdef CONFIG_FOO_MODEL_TWO + /* Code for model two */ + #endif + + Now suppose the user (the person building kernels) reconfigures the + kernel to change some unrelated setting. This will regenerate the + file include/linux/autoconf.h, which will cause include/linux/config.h + to be out of date, which will cause drivers/net/foo.c to be recompiled. + + Most kernel sources, perhaps 80% of them, have at least one CONFIG_* + dependency somewhere. So changing _any_ CONFIG_* setting requires + almost _all_ of the kernel to be recompiled. + +Here is the solution: + + We've made the dependency generator, mkdep.c, smarter. Instead of + generating this dependency: + + drivers/net/foo.c: include/linux/config.h + + It now generates these dependencies: + + drivers/net/foo.c: \ + include/config/foo/autofrob.h \ + include/config/foo/model/two.h + + So drivers/net/foo.c depends only on the CONFIG_* lines that + it actually uses. + + A new program, split-include.c, runs at the beginning of + compilation (make bzImage or make zImage). split-include reads + include/linux/autoconf.h and updates the include/config/ tree, + writing one file per option. It updates only the files for options + that have changed. + +Flag Dependencies + + Martin Von Loewis contributed another feature to this patch: + 'flag dependencies'. The idea is that a .o file depends on + the compilation flags used to build it. The file foo.o has + its flags stored in .flags.foo.o. + + Suppose the user changes the foo driver from resident to modular. + 'make' will notice that the current foo.o was not compiled with + -DMODULE and will recompile foo.c. + + All .o files made from C source have flag dependencies. So do .o + files made with ld, and .a files made with ar. However, .o files + made from assembly source do not have flag dependencies (nobody + needs this yet, but it would be good to fix). + +Per-source-file Flags + + Flag dependencies also work with per-source-file flags. + You can specify compilation flags for individual source files + like this: + + CFLAGS_foo.o = -DSPECIAL_FOO_DEFINE + + This helps clean up drivers/net/Makefile, drivers/scsi/Makefile, + and several other Makefiles. + +Credit + + Werner Almesberger had the original idea and wrote the first + version of this patch. + + Michael Chastain picked it up and continued development. He is + now the principal author and maintainer. Please report any bugs + to him. + + Martin von Loewis wrote flag dependencies, with some modifications + by Michael Chastain. + + Thanks to all of the beta testers. --- linux-2.6.25-rc3-git4.orig/Documentation/smart-config.txt +++ /dev/null @@ -1,98 +0,0 @@ -Smart CONFIG_* Dependencies -1 August 1999 - -Michael Chastain <mec@xxxxxxxxx> -Werner Almesberger <almesber@xxxxxxxxxxxxxx> -Martin von Loewis <martin@xxxxxxxxxxxxxxxxxxxxxxxxx> - -Here is the problem: - - Suppose that drivers/net/foo.c has the following lines: - - #include <linux/config.h> - - ... - - #ifdef CONFIG_FOO_AUTOFROB - /* Code for auto-frobbing */ - #else - /* Manual frobbing only */ - #endif - - ... - - #ifdef CONFIG_FOO_MODEL_TWO - /* Code for model two */ - #endif - - Now suppose the user (the person building kernels) reconfigures the - kernel to change some unrelated setting. This will regenerate the - file include/linux/autoconf.h, which will cause include/linux/config.h - to be out of date, which will cause drivers/net/foo.c to be recompiled. - - Most kernel sources, perhaps 80% of them, have at least one CONFIG_* - dependency somewhere. So changing _any_ CONFIG_* setting requires - almost _all_ of the kernel to be recompiled. - -Here is the solution: - - We've made the dependency generator, mkdep.c, smarter. Instead of - generating this dependency: - - drivers/net/foo.c: include/linux/config.h - - It now generates these dependencies: - - drivers/net/foo.c: \ - include/config/foo/autofrob.h \ - include/config/foo/model/two.h - - So drivers/net/foo.c depends only on the CONFIG_* lines that - it actually uses. - - A new program, split-include.c, runs at the beginning of - compilation (make bzImage or make zImage). split-include reads - include/linux/autoconf.h and updates the include/config/ tree, - writing one file per option. It updates only the files for options - that have changed. - -Flag Dependencies - - Martin Von Loewis contributed another feature to this patch: - 'flag dependencies'. The idea is that a .o file depends on - the compilation flags used to build it. The file foo.o has - its flags stored in .flags.foo.o. - - Suppose the user changes the foo driver from resident to modular. - 'make' will notice that the current foo.o was not compiled with - -DMODULE and will recompile foo.c. - - All .o files made from C source have flag dependencies. So do .o - files made with ld, and .a files made with ar. However, .o files - made from assembly source do not have flag dependencies (nobody - needs this yet, but it would be good to fix). - -Per-source-file Flags - - Flag dependencies also work with per-source-file flags. - You can specify compilation flags for individual source files - like this: - - CFLAGS_foo.o = -DSPECIAL_FOO_DEFINE - - This helps clean up drivers/net/Makefile, drivers/scsi/Makefile, - and several other Makefiles. - -Credit - - Werner Almesberger had the original idea and wrote the first - version of this patch. - - Michael Chastain picked it up and continued development. He is - now the principal author and maintainer. Please report any bugs - to him. - - Martin von Loewis wrote flag dependencies, with some modifications - by Michael Chastain. - - Thanks to all of the beta testers. -- 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
