kbuild: redo fake deps at include/config/*.h

Make include/config/foo/bar.h fake deps files generation simpler.

* delete .h suffix
those aren't header files, shorten filenames,

* delete tolower()
Linux filesystems can deal with both upper and lowercase
filenames very well,

* put everything in 1 directory
Presumably 'mkdir -p' split is from dark times when filesystems
handled huge directories badly, disks were round adding to
seek times.

x86_64 allmodconfig lists 12364 files in include/config.

../obj/include/config/
├── 104_QUAD_8
├── 60XX_WDT
├── 64BIT
...
├── ZSWAP_DEFAULT_ON
├── ZSWAP_ZPOOL_DEFAULT
└── ZSWAP_ZPOOL_DEFAULT_ZBUD

0 directories, 12364 files

Signed-off-by: Alexey Dobriyan <[e-mail]>
Signed-off-by: Masahiro Yamada <[e-mail]>

include/linux/compiler-version.h

···
  * This header exists to force full rebuild when the compiler is upgraded.
  *
  * When fixdep scans this, it will find this string "CONFIG_CC_VERSION_TEXT"
- * and add dependency on include/config/cc/version/text.h, which is touched
+ * and add dependency on include/config/CC_VERSION_TEXT, which is touched
  * by Kconfig when the version string from the compiler changes.
  */

init/Kconfig

···
 
 	  - Ensure full rebuild when the compiler is updated
 	    include/linux/compiler-version.h contains this option in the comment
-	    line so fixdep adds include/config/cc/version/text.h into the
+	    line so fixdep adds include/config/CC_VERSION_TEXT into the
 	    auto-generated dependency. When the compiler is updated, syncconfig
 	    will touch it and then every file will be rebuilt.
 

kernel/gen_kheaders.sh

···
 #
 # When Kconfig regenerates include/generated/autoconf.h, its timestamp is
 # updated, but the contents might be still the same. When any CONFIG option is
-# changed, Kconfig touches the corresponding timestamp file include/config/*.h.
+# changed, Kconfig touches the corresponding timestamp file include/config/*.
 # Hence, the md5sum detects the configuration change anyway. We do not need to
 # check include/generated/autoconf.h explicitly.
 #

scripts/Makefile.build

···
 
 # Rebuild all objects when objtool changes, or is enabled/disabled.
 objtool_dep = $(objtool_obj)					\
-	      $(wildcard include/config/orc/unwinder.h		\
-			 include/config/stack/validation.h)
+	      $(wildcard include/config/ORC_UNWINDER		\
+			 include/config/STACK_VALIDATION)
 
 ifdef CONFIG_TRIM_UNUSED_KSYMS
 cmd_gen_ksymdeps = \

scripts/basic/fixdep.c

···
  * the config symbols are rebuilt.
  *
  * So if the user changes his CONFIG_HIS_DRIVER option, only the objects
- * which depend on "include/config/his/driver.h" will be rebuilt,
+ * which depend on "include/config/HIS_DRIVER" will be rebuilt,
  * so most likely only his driver ;-)
  *
  * The idea above dates, by the way, back to Michael E Chastain, AFAIK.
···
  *
  * and then basically copies the .<target>.d file to stdout, in the
  * process filtering out the dependency on autoconf.h and adding
- * dependencies on include/config/my/option.h for every
+ * dependencies on include/config/MY_OPTION for every
  * CONFIG_MY_OPTION encountered in any of the prerequisites.
  *
  * We don't even try to really parse the header files, but
···
 
 /*
  * In the intended usage of this program, the stdout is redirected to .*.cmd
- * files. The return value of printf() and putchar() must be checked to catch
- * any error, e.g. "No space left on device".
+ * files. The return value of printf() must be checked to catch any error,
+ * e.g. "No space left on device".
  */
 static void xprintf(const char *format, ...)
 {
···
 		exit(1);
 	}
 	va_end(ap);
-}
-
-static void xputchar(int c)
-{
-	int ret;
-
-	ret = putchar(c);
-	if (ret == EOF) {
-		perror("fixdep");
-		exit(1);
-	}
-}
-
-/*
- * Print out a dependency path from a symbol name
- */
-static void print_dep(const char *m, int slen, const char *dir)
-{
-	int c, prev_c = '/', i;
-
-	xprintf("    $(wildcard %s/", dir);
-	for (i = 0; i < slen; i++) {
-		c = m[i];
-		if (c == '_')
-			c = '/';
-		else
-			c = tolower(c);
-		if (c != '/' || prev_c != '/')
-			xputchar(c);
-		prev_c = c;
-	}
-	xprintf(".h) \\\n");
 }
 
 struct item {
···
 	    return;
 
 	define_config(m, slen, hash);
-	print_dep(m, slen, "include/config");
+	/* Print out a dependency path from a symbol name. */
+	xprintf("    $(wildcard include/config/%.*s) \\\n", slen, m);
 }
 
 /* test if s ends in sub */

scripts/kconfig/confdata.c

···
 static int conf_touch_dep(const char *name)
 {
 	int fd, ret;
-	const char *s;
-	char *d, c;
+	char *d;
 
-	/* check overflow: prefix + name + ".h" + '\0' must fit in buffer. */
-	if (depfile_prefix_len + strlen(name) + 3 > sizeof(depfile_path))
+	/* check overflow: prefix + name + '\0' must fit in buffer. */
+	if (depfile_prefix_len + strlen(name) + 1 > sizeof(depfile_path))
 		return -1;
 
 	d = depfile_path + depfile_prefix_len;
-	s = name;
-
-	while ((c = *s++))
-		*d++ = (c == '_') ? '/' : tolower(c);
-	strcpy(d, ".h");
+	strcpy(d, name);
 
 	/* Assume directory path already exists. */
 	fd = open(depfile_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
···
 					 * Reading from include/config/auto.conf
 					 * If CONFIG_FOO previously existed in
 					 * auto.conf but it is missing now,
-					 * include/config/foo.h must be touched.
+					 * include/config/FOO must be touched.
 					 */
 					conf_touch_dep(line + strlen(CONFIG_));
 				else