streamline_config.pl: add LMC_KEEP to preserve some kconfigs

Sometimes it is useful to preserve batches of configs when making
localmodconfig. For example, I usually don't want any usb and fs
modules to be disabled. Now we can do it by:

 $ make LMC_KEEP="drivers/usb:fs" localmodconfig

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

2 files changed, 23 insertions, 0 deletions

diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index c9d0a4a8efb3..f3355bd86aa5 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -123,7 +123,9 @@ help:
 	@echo  '  gconfig	  - Update current config utilising a GTK+ based front-end'
 	@echo  '  oldconfig	  - Update current config utilising a provided .config as base'
 	@echo  '  localmodconfig  - Update current config disabling modules not loaded'
+	@echo  '                    except those preserved by LMC_KEEP environment variable'
 	@echo  '  localyesconfig  - Update current config converting local mods to core'
+	@echo  '                    except those preserved by LMC_KEEP environment variable'
 	@echo  '  defconfig	  - New config with default from ARCH supplied defconfig'
 	@echo  '  savedefconfig   - Save current config as ./defconfig (minimal config)'
 	@echo  '  allnoconfig	  - New config where all options are answered with no'
diff --git a/scripts/kconfig/streamline_config.pl b/scripts/kconfig/streamline_config.pl
index e2f8504f5a2d..19857d18d814 100755
--- a/scripts/kconfig/streamline_config.pl
+++ b/scripts/kconfig/streamline_config.pl
@@ -143,6 +143,7 @@ my %depends;
 my %selects;
 my %prompts;
 my %objects;
+my %config2kfile;
 my $var;
 my $iflevel = 0;
 my @ifdeps;
@@ -201,6 +202,7 @@ sub read_kconfig {
 	if (/^\s*(menu)?config\s+(\S+)\s*$/) {
 	    $state = "NEW";
 	    $config = $2;
+	    $config2kfile{"CONFIG_$config"} = $kconfig;
 
 	    # Add depends for 'if' nesting
 	    for (my $i = 0; $i < $iflevel; $i++) {
@@ -591,6 +593,20 @@ while ($repeat) {
 }
 
 my %setconfigs;
+my @preserved_kconfigs = split(/:/,$ENV{LMC_KEEP});
+
+sub in_preserved_kconfigs {
+    my $kconfig = $config2kfile{$_[0]};
+    if (!defined($kconfig)) {
+        return 0;
+    }
+    foreach my $excl (@preserved_kconfigs) {
+        if($kconfig =~ /^$excl/) {
+            return 1;
+        }
+    }
+    return 0;
+}
 
 # Finally, read the .config file and turn off any module enabled that
 # we could not find a reason to keep enabled.
@@ -644,6 +660,11 @@ foreach my $line (@config_file) {
     }
 
     if (/^(CONFIG.*)=(m|y)/) {
+        if (in_preserved_kconfigs($1)) {
+            dprint "Preserve config $1";
+            print;
+            next;
+        }
 	if (defined($configs{$1})) {
 	    if ($localyesconfig) {
 	        $setconfigs{$1} = 'y';