checkpatch: allow passing config directory

checkpatch.pl searches for .checkpatch.conf in $CWD, $HOME and
$CWD/.scripts.  Allow passing a single directory via CHECKPATCH_CONFIG_DIR
environment variable (empty value is ignored).  This allows to directly
use project configuration file for projects which vendored checkpatch.pl
(e.g.  LTP or u-boot).

Although it'd be more convenient for user to have --conf-dir option
(instead of using environment variable), code would get ugly because
options from the configuration file needs to be read before processing
command line options with Getopt::Long.

While at it, document directories and environment variable in -h help
and HTML doc.

Link: https://lore.kernel.org/20260421211408.383972-1-pvorel@suse.cz
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Perches <joe@perches.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 17 insertions, 3 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 0492d6afc9a1..8b44b3a6a4dd 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -57,6 +57,9 @@ my %ignore_type = ();
 my @ignore = ();
 my $help = 0;
 my $configuration_file = ".checkpatch.conf";
+my $def_configuration_dirs_help = '.:$HOME:.scripts';
+(my $def_configuration_dirs = $def_configuration_dirs_help) =~ s/\$(\w+)/$ENV{$1}/g;
+my $env_config_dir = 'CHECKPATCH_CONFIG_DIR';
 my $max_line_length = 100;
 my $ignore_perl_version = 0;
 my $minimum_perl_version = 5.10.0;
@@ -146,6 +149,11 @@ Options:
   -h, --help, --version      display this help and exit
 
 When FILE is - read standard input.
+
+CONFIGURATION FILE
+Default configuration options can be stored in $configuration_file,
+search path: '$def_configuration_dirs_help' or in a directory specified by
+\$$env_config_dir environment variable (fallback to the default search path).
 EOM
 
 	exit($exitcode);
@@ -237,7 +245,7 @@ sub list_types {
 	exit($exitcode);
 }
 
-my $conf = which_conf($configuration_file);
+my $conf = which_conf($configuration_file, $env_config_dir, $def_configuration_dirs);
 if (-f $conf) {
 	my @conf_args;
 	open(my $conffile, '<', "$conf")
@@ -1531,9 +1539,15 @@ sub which {
 }
 
 sub which_conf {
-	my ($conf) = @_;
+	my ($conf, $env_key, $paths) = @_;
+	my $env_dir = $ENV{$env_key};
+
+	if (defined($env_dir) && $env_dir ne "") {
+		return "$env_dir/$conf" if (-e "$env_dir/$conf");
+		warn "$P: Can't find a readable $conf in '$env_dir', falling back to default search paths\n";
+	}
 
-	foreach my $path (split(/:/, ".:$ENV{HOME}:.scripts")) {
+	foreach my $path (split(/:/, $paths)) {
 		if (-e "$path/$conf") {
 			return "$path/$conf";
 		}