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# Copyright 2005-2009 - Steven Rostedt
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# Licensed under the terms of the GNU GPL License version 2
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# It's simple enough to figure out how this works.
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# If not, then you can ask me at stripconfig@goodmis.org
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# If you have installed a Linux kernel from a distribution
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# that turns on way too many modules than you need, and
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# you only want the modules you use, then this program
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# It gives you the ability to turn off all the modules that are
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# not loaded on your system.
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# 1. Boot up the kernel that you want to stream line the config on.
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# 2. Change directory to the directory holding the source of the
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# kernel that you just booted.
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# 3. Copy the configuraton file to this directory as .config
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# 4. Have all your devices that you need modules for connected and
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# operational (make sure that their corresponding modules are loaded)
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# 5. Run this script redirecting the output to some other file
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# 6. Back up your old config (if you want too).
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# 7. copy the config_strip file to .config
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# 8. Run "make oldconfig"
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# Now your kernel is ready to be built with only the modules that
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# Here's what I did with my Debian distribution.
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# cd /usr/src/linux-2.6.10
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# cp /boot/config-2.6.10-1-686-smp .config
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# ~/bin/streamline_config > config_strip
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# mv .config config_sav
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# mv config_strip .config
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# set the environment variable LOCALMODCONFIG_DEBUG to get
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$debugprint = 1 if (defined($ENV{LOCALMODCONFIG_DEBUG}));
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return if (!$debugprint);
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my $config = ".config";
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my $uname = `uname -r`;
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"file" => "/proc/config.gz",
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"file" => "/boot/config-$uname",
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"file" => "/boot/vmlinuz-$uname",
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"exec" => "scripts/extract-ikconfig",
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"test" => "scripts/extract-ikconfig",
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"exec" => "scripts/extract-ikconfig",
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"test" => "scripts/extract-ikconfig",
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"file" => "/lib/modules/$uname/kernel/kernel/configs.ko",
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"exec" => "scripts/extract-ikconfig",
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"test" => "scripts/extract-ikconfig",
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"file" => "kernel/configs.ko",
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"exec" => "scripts/extract-ikconfig",
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"test" => "scripts/extract-ikconfig",
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"file" => "kernel/configs.o",
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"exec" => "scripts/extract-ikconfig",
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"test" => "scripts/extract-ikconfig",
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foreach my $conf (@searchconfigs) {
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my $file = $conf->{"file"};
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next if ( ! -f "$file");
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if (defined($conf->{"test"})) {
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`$conf->{"test"} $conf->{"file"} 2>/dev/null`;
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my $exec = $conf->{"exec"};
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print STDERR "using config: '$file'\n";
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open(my $infile, '-|', "$exec $file") || die "Failed to run $exec $file";
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die "No config file found";
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my @config_file = read_config;
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my $localmodconfig = 0;
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my $localyesconfig = 0;
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GetOptions("localmodconfig" => \$localmodconfig,
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"localyesconfig" => \$localyesconfig);
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# Get the build source and top level Kconfig file (passed in)
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my $ksource = ($ARGV[0] ? $ARGV[0] : '.');
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my $kconfig = $ARGV[1];
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my $lsmod_file = $ENV{'LSMOD'};
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my @makefiles = `find $ksource -name Makefile 2>/dev/null`;
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my $source = "$ksource/$kconfig";
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my $last_source = "";
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# Check for any environment variables used
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while ($source =~ /\$(\w+)/ && $last_source ne $source) {
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$last_source = $source;
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$source =~ s/\$$env/$ENV{$env}/;
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open(my $kinfile, '<', $source) || die "Can't open $kconfig";
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# Make sure that lines ending with \ continue
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$_ = $line . " " . $_;
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# collect any Kconfig sources
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if (/^source\s*"(.*)"/) {
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# prevent reading twice.
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if (!defined($read_kconfigs{$kconfig})) {
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$read_kconfigs{$kconfig} = 1;
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read_kconfig($kconfig);
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if (/^\s*(menu)?config\s+(\S+)\s*$/) {
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# Add depends for 'if' nesting
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for (my $i = 0; $i < $iflevel; $i++) {
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$depends{$config} .= " " . $ifdeps[$i];
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$depends{$config} = $ifdeps[$i];
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# collect the depends for the config
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} elsif ($state eq "NEW" && /^\s*depends\s+on\s+(.*)$/) {
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$depends{$config} = $1;
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} elsif ($state eq "DEP" && /^\s*depends\s+on\s+(.*)$/) {
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$depends{$config} .= " " . $1;
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} elsif ($state eq "DEP" && /^\s*def(_(bool|tristate)|ault)\s+(\S.*)$/) {
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if ($dep !~ /^\s*(y|m|n)\s*$/) {
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$dep =~ s/.*\sif\s+//;
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$depends{$config} .= " " . $dep;
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dprint "Added default depends $dep to $config\n";
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# Get the configs that select this config
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} elsif ($state ne "NONE" && /^\s*select\s+(\S+)/) {
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if (defined($selects{$conf})) {
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$selects{$conf} .= " " . $config;
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$selects{$conf} = $config;
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# configs without prompts must be selected
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} elsif ($state ne "NONE" && /^\s*tristate\s\S/) {
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# note if the config has a prompt
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$prompts{$config} = 1;
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# Check for if statements
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} elsif (/^if\s+(.*\S)\s*$/) {
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# remove beginning and ending non text
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$deps =~ s/^[^a-zA-Z0-9_]*//;
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$deps =~ s/[^a-zA-Z0-9_]*$//;
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my @deps = split /[^a-zA-Z0-9_]+/, $deps;
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$ifdeps[$iflevel++] = join ':', @deps;
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$iflevel-- if ($iflevel);
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} elsif (/^\s*help\s*$/) {
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read_kconfig($kconfig);
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# Makefiles can use variables to define their dependencies
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my ($line, %vars) = @_;
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while ($line =~ s/^(.*?)(\$\((.*?)\))//) {
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if (defined($vars{$var})) {
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$process .= $start . $vars{$var};
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$process .= $start . $variable;
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# Read all Makefiles to map the configs to the objects
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foreach my $makefile (@makefiles) {
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open(my $infile, '<', $makefile) || die "Can't open $makefile";
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# if this line ends with a backslash, continue
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# Convert variables in a line (could define configs)
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$_ = convert_vars($_, %make_vars);
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# collect objects after obj-$(CONFIG_FOO_BAR)
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if (/obj-\$\((CONFIG_[^\)]*)\)\s*[+:]?=\s*(.*)/) {
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# check if variables are set
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} elsif (/^\s*(\S+)\s*[:]?=\s*(.*\S)/) {
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if (defined($objs)) {
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foreach my $obj (split /\s+/,$objs) {
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if ($obj =~ /(.*)\.o$/) {
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# Objects may be enabled by more than one config.
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# Store configs in an array.
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if (defined($objects{$1})) {
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@arr = @{$objects{$1}};
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$arr[$#arr+1] = $var;
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# The objects have a hash mapping to a reference
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# of an array of configs.
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$objects{$1} = \@arr;
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if (defined($lsmod_file)) {
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if ( ! -f $lsmod_file) {
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if ( -f $ENV{'objtree'}."/".$lsmod_file) {
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$lsmod_file = $ENV{'objtree'}."/".$lsmod_file;
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die "$lsmod_file not found";
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my $otype = ( -x $lsmod_file) ? '-|' : '<';
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open($linfile, $otype, $lsmod_file);
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# see what modules are loaded on this system
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foreach my $dir ( ("/sbin", "/bin", "/usr/sbin", "/usr/bin") ) {
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if ( -x "$dir/lsmod" ) {
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$lsmod = "$dir/lsmod";
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if (!defined($lsmod)) {
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open($linfile, '-|', $lsmod) || die "Can not call lsmod with $lsmod";
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next if (/^Module/); # Skip the first line.
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# add to the configs hash all configs that are needed to enable
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# a loaded module. This is a direct obj-${CONFIG_FOO} += bar.o
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# where we know we need bar.o so we add FOO to the list.
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foreach my $module (keys(%modules)) {
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if (defined($objects{$module})) {
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my @arr = @{$objects{$module}};
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foreach my $conf (@arr) {
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$configs{$conf} = $module;
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dprint "$conf added by direct ($module)\n";
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if (defined($depends{$c})) {
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dprint " deps = $depends{$c}\n";
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# Most likely, someone has a custom (binary?) module loaded.
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print STDERR "$module config not found!!\n";
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# Read the current config, and see what is enabled. We want to
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# ignore configs that we would not enable anyway.
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my $valid = "A-Za-z_0-9";
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foreach my $line (@config_file) {
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if (/(CONFIG_[$valid]*)=(m|y)/) {
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$orig_configs{$1} = $2;
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# Note, we do not care about operands (like: &&, ||, !) we want to add any
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# config that is in the depend list of another config. This script does
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# not enable configs that are not already enabled. If we come across a
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# config A that depends on !B, we can still add B to the list of depends
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# to keep on. If A was on in the original config, B would not have been
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# and B would not be turned on by this script.
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sub parse_config_depends
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while ($p =~ /[$valid]/) {
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if ($p =~ /^[^$valid]*([$valid]+)/) {
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my $conf = "CONFIG_" . $1;
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$p =~ s/^[^$valid]*[$valid]+//;
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# We only need to process if the depend config is a module
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if (!defined($orig_configs{$conf}) || !$orig_configs{conf} eq "m") {
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if (!defined($configs{$conf})) {
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# We must make sure that this config has its
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$repeat = 1; # do again
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dprint "$conf selected by depend $depconfig\n";
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die "this should never happen";
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# Select is treated a bit differently than depends. We call this
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# when a config has no prompt and requires another config to be
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# selected. We use to just select all configs that selected this
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# config, but found that that can balloon into enabling hundreds
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# of configs that we do not care about.
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# The idea is we look at all the configs that select it. If one
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# is already in our list of configs to enable, then there's nothing
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# else to do. If there isn't, we pick the first config that was
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# enabled in the orignal config and use that.
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sub parse_config_selects
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my ($config, $p) = @_;
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while ($p =~ /[$valid]/) {
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if ($p =~ /^[^$valid]*([$valid]+)/) {
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my $conf = "CONFIG_" . $1;
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$p =~ s/^[^$valid]*[$valid]+//;
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# Make sure that this config exists in the current .config file
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if (!defined($orig_configs{$conf})) {
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dprint "$conf not set for $config select\n";
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# Check if something other than a module selects this config
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if (defined($orig_configs{$conf}) && $orig_configs{$conf} ne "m") {
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dprint "$conf (non module) selects config, we are good\n";
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# we are good with this
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if (defined($configs{$conf})) {
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dprint "$conf selects $config so we are good\n";
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# A set config selects this config, we are good
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# Set this config to be selected
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if (!defined($next_config)) {
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$next_config = $conf;
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die "this should never happen";
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# If no possible config selected this, then something happened.
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if (!defined($next_config)) {
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print STDERR "WARNING: $config is required, but nothing in the\n";
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print STDERR " current config selects it.\n";
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# If we are here, then we found no config that is set and
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# selects this config. Repeat.
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# Make this config need to be selected
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$configs{$next_config} = 1;
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dprint "$next_config selected by select $config\n";
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# loop through all configs, select their dependencies.
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foreach my $config (keys %configs) {
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# If this config is not a module, we do not need to process it
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if (defined($orig_configs{$config}) && $orig_configs{$config} ne "m") {
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$config =~ s/^CONFIG_//;
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$depconfig = $config;
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if (defined($depends{$config})) {
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# This config has dependencies. Make sure they are also included
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parse_config_depends $depends{$config};
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# If the config has no prompt, then we need to check if a config
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# that is enabled selected it. Or if we need to enable one.
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if (!defined($prompts{$config}) && defined($selects{$config})) {
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$process_selects{$config} = 1;
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foreach my $config (keys %process_selects) {
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$config =~ s/^CONFIG_//;
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dprint "Process select $config\n";
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# config has no prompt and must be selected.
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parse_config_selects $config, $selects{$config};
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# Get the first set of configs and their dependencies.
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# Now we need to see if we have to check selects;
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# Finally, read the .config file and turn off any module enabled that
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# we could not find a reason to keep enabled.
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foreach my $line (@config_file) {
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if (/CONFIG_IKCONFIG/) {
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if (/# CONFIG_IKCONFIG is not set/) {
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# enable IKCONFIG at least as a module
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print "CONFIG_IKCONFIG=m\n";
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# don't ask about PROC
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print "# CONFIG_IKCONFIG_PROC is not set\n";
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if (/^(CONFIG.*)=(m|y)/) {
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if (defined($configs{$1})) {
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if ($localyesconfig) {
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$setconfigs{$1} = 'y';
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$setconfigs{$1} = $2;
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} elsif ($2 eq "m") {
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print "# $1 is not set\n";
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# Integrity check, make sure all modules that we want enabled do
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# indeed have their configs set.
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foreach my $module (keys(%modules)) {
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if (defined($objects{$module})) {
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my @arr = @{$objects{$module}};
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foreach my $conf (@arr) {
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if (defined($setconfigs{$conf})) {
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print STDERR "module $module did not have configs";
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foreach my $conf (@arr) {
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print STDERR " " , $conf;