Support giving the header path in KCONFIG_AUTOHEADER

This environment variable is used by the C tools. Use it when
filename=None is passed to write_autoconf(), and default to
include/generated/autoconf.h for compatibility.

Also update genconfig.py to use KCONFIG_AUTOHEADER if set when no
--header-path is passed. If KCONFIG_AUTOHEADER isn't set, keep
defaulting to 'config.h' for backwards compatibility. It's probably a
saner default for tools as well.

2 files changed, 30 insertions, 11 deletions

diff --git a/genconfig.py b/genconfig.py
index 96124c5..b202a5b 100755
--- a/genconfig.py
+++ b/genconfig.py
@@ -35,7 +35,6 @@ import sys
 import kconfiglib
 
 
-DEFAULT_HEADER_PATH = "config.h"
 DEFAULT_SYNC_DEPS_PATH = "deps/"
 
 
@@ -47,9 +46,11 @@ def main():
     parser.add_argument(
         "--header-path",
         metavar="HEADER_FILE",
-        default=DEFAULT_HEADER_PATH,
-        help="Path for the generated header file (default: {})"
-             .format(DEFAULT_HEADER_PATH))
+        help="""
+Path to write the generated header file to. If not specified, the path in the
+environment variable KCONFIG_AUTOHEADER is used if it is set, and 'config.h'
+otherwise.
+""")
 
     parser.add_argument(
         "--config-out",
@@ -107,7 +108,17 @@ only supported for backwards compatibility).
     kconf = kconfiglib.Kconfig(args.kconfig_filename)
     kconf.load_config()
 
-    kconf.write_autoconf(args.header_path)
+    if args.header_path is None:
+        if "KCONFIG_AUTOHEADER" in os.environ:
+            kconf.write_autoconf()
+        else:
+            # Kconfiglib defaults to include/generated/autoconf.h to be
+            # compatible with the C tools. 'config.h' is used here instead for
+            # backwards compatibility. It's probably a saner default for tools
+            # as well.
+            kconf.write_autoconf("config.h")
+    else:
+        kconf.write_autoconf(args.header_path)
 
     if args.config_out is not None:
         kconf.write_config(args.config_out, save_old=False)
diff --git a/kconfiglib.py b/kconfiglib.py
index 079c363..7fe3f2e 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -1363,7 +1363,7 @@ class Kconfig(object):
         elif self.warn_assign_override:
             self._warn(msg, filename, linenr)
 
-    def write_autoconf(self, filename, header=None):
+    def write_autoconf(self, filename=None, header=None):
         r"""
         Writes out symbol values as a C header file, matching the format used
         by include/generated/autoconf.h in the kernel.
@@ -1377,8 +1377,12 @@ class Kconfig(object):
         like the modification time and possibly triggering redundant work in
         build tools.
 
-        filename:
-          Self-explanatory.
+        filename (default: None):
+          Path to write header to.
+
+          If None (the default), the path in the environment variable
+          KCONFIG_AUTOHEADER is used if set, and "include/generated/autoconf.h"
+          otherwise. This is compatible with the C tools.
 
         header (default: None):
           Text inserted verbatim at the beginning of the file. You would
@@ -1390,6 +1394,10 @@ class Kconfig(object):
           will be used if it was set, and no header otherwise. See the
           Kconfig.header_header attribute.
         """
+        if filename is None:
+            filename = os.getenv("KCONFIG_AUTOHEADER",
+                                 "include/generated/autoconf.h")
+
         self._write_if_changed(filename, self._autoconf_contents(header))
 
     def _autoconf_contents(self, header):
@@ -1458,9 +1466,9 @@ class Kconfig(object):
         (OSError/IOError). KconfigError is never raised here.
 
         filename (default: None):
-          Filename to save configuration to (a string).
+          Path to write configuration to (a string).
 
-          If None (the default), the filename in the environment variable
+          If None (the default), the path in the environment variable
           KCONFIG_CONFIG is used if set, and ".config" otherwise. See
           standard_config_filename().
 
@@ -1606,7 +1614,7 @@ class Kconfig(object):
         (OSError/IOError). KconfigError is never raised here.
 
         filename:
-          Self-explanatory.
+          Path to write minimal configuration to.
 
         header (default: None):
           Text inserted verbatim at the beginning of the file. You would