linux kernel make tag variable

Question

Linux kernel source can use make tags to get the tag for editor. In scripts/tags.sh, line7 and line8 say that "Uses the following environment variables: ARCH, SUBARCH, SRCARCH, srctree, src, obj" I want to ask What are these variable meaning?

I already read this article,but it just mention the two vairables, SRCARCH and SUBARCH.

Answer 1

Variables you should use

Next variables can be passed to tags.sh (actually you should pass them to make tags cscope command, and Makefile will pass them to tags.sh for you).

1. ARCH: which architecture to index. You can see all architectures list just by doing ls -l arch/ in your kernel source tree.

2. SUBARCH: the meaning of this variable depends on your architecture:

   • if ARCH=arm, SUBARCH will be used to determine arch/arm/mach-* and arch/arm/plat-* directories, and these directories will be indexed
   • if ARCH=um, use SUBARCH to specify which architecture you actually want to use in your User-Mode Linux (like SUBARCH=arm or SUBARCH=x86)
   • for the rest of architectures, you can omit this variable

3. ALLSOURCE_ARCHS: use this to index more than one architecture. Like ALLSOURCE_ARCHS="x86 mips arm" or ALLSOURCE_ARCHS="all". If you only want to index one architecture, omit this variable and use ARCH instead.

4. COMPILED_SOURCE: set this variable to 1 if you want to index only actually compiled source files. If you want to index all source files, omit setting this variable.

5. O= (this is actually Makefile parameter): use absolute paths (useful if you want to load created cscope/ctags index files outside of kernel directory, e.g. for development of out-of-tree kernel modules). If you want to use relative paths (i.e. you're gonna do development only in kernel dir), just omit that parameter.

Variables you don't need to touch

1. SRCARCH: being set from ARCH variable in Makefile and then passed to script. You probably don't need to mess with it, just set ARCH variable correctly

2. srctree: kernel source tree path. This variable will be passed from Makefile automatically if you're using this script via make cscope tags.

3. src and obj variables: those are not used by scripts/tags.sh anymore. It was replaced by utilizing KBUILD_SRC variable, which is provided from Makefile automatically, when you provide O=... parameter to it.

Usage

Basically, I'd recommend to only use scripts/tags.sh via make invocation. Example:

$ make O=. ARCH=arm SUBARCH=omap2 COMPILED_SOURCE=1 cscope tags

or

$ make ARCH=x86 cscope tags