tools/docs/get_feat.py: convert get_feat.pl to Python

As we want to call Python code directly at the Sphinx extension,
convert get_feat.pl to Python.

The code was made to be (almost) bug-compatible with the Perl
version, with two exceptions:

1. Currently, Perl script outputs a wrong table if arch is set
   to a non-existing value;

2. the ReST table output when --feat is used without --arch
   has an invalid format, as the number of characters for the
   table delimiters are wrong.

Those two bugs were fixed while testing the conversion.

Additionally, another caveat was solved:
the output when --feat is used without arch and the feature
doesn't exist doesn't contain an empty table anymore.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <03c26cee1ec567804735a33047e625ef5ab7bfa8.1763492868.git.mchehab+huawei@kernel.org>

tools/docs/get_feat.py

@@ -0,0 +1,225 @@
+#!/usr/bin/env python3
+# pylint: disable=R0902,R0911,R0912,R0914,R0915
+# Copyright(c) 2025: Mauro Carvalho Chehab <mchehab@kernel.org>.
+# SPDX-License-Identifier: GPL-2.0
+
+
+"""
+Parse the Linux Feature files and produce a ReST book.
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+
+from pprint import pprint
+
+LIB_DIR = "../../tools/lib/python"
+SRC_DIR = os.path.dirname(os.path.realpath(__file__))
+
+sys.path.insert(0, os.path.join(SRC_DIR, LIB_DIR))
+
+from feat.parse_features import ParseFeature                # pylint: disable=C0413
+
+SRCTREE = os.path.join(os.path.dirname(os.path.realpath(__file__)), "../..")
+DEFAULT_DIR = "Documentation/features"
+
+
+class GetFeature:
+    """Helper class to parse feature parsing parameters"""
+
+    @staticmethod
+    def get_current_arch():
+        """Detects the current architecture"""
+
+        proc = subprocess.run(["uname", "-m"], check=True,
+                              capture_output=True, text=True)
+
+        arch = proc.stdout.strip()
+        if arch in ["x86_64", "i386"]:
+            arch = "x86"
+        elif arch == "s390x":
+            arch = "s390"
+
+        return arch
+
+    def run_parser(self, args):
+        """Execute the feature parser"""
+
+        feat = ParseFeature(args.directory, args.debug, args.enable_fname)
+        data = feat.parse()
+
+        if args.debug > 2:
+            pprint(data)
+
+        return feat
+
+    def run_rest(self, args):
+        """
+        Generate tables in ReST format. Three types of tables are
+        supported, depending on the calling arguments:
+
+        - neither feature nor arch is passed: generates a full matrix;
+        - arch provided: generates a table of supported tables for the
+          guiven architecture, eventually filtered by feature;
+        - only feature provided: generates a table with feature details,
+          showing what architectures it is implemented.
+        """
+
+        feat = self.run_parser(args)
+
+        if args.arch:
+            rst = feat.output_arch_table(args.arch, args.feat)
+        elif args.feat:
+            rst = feat.output_feature(args.feat)
+        else:
+            rst = feat.output_matrix()
+
+        print(rst)
+
+    def run_current(self, args):
+        """
+        Instead of using a --arch parameter, get feature for the current
+        architecture.
+        """
+
+        args.arch = self.get_current_arch()
+
+        self.run_rest(args)
+
+    def run_list(self, args):
+        """
+        Generate a list of features for a given architecture, in a format
+        parseable by other scripts. The output format is not ReST.
+        """
+
+        if not args.arch:
+            args.arch = self.get_current_arch()
+
+        feat = self.run_parser(args)
+        msg = feat.list_arch_features(args.arch, args.feat)
+
+        print(msg)
+
+    def parse_arch(self, parser):
+        """Add a --arch parsing argument"""
+
+        parser.add_argument("--arch",
+                            help="Output features for an specific"
+                                 " architecture, optionally filtering for a "
+                                 "single specific feature.")
+
+    def parse_feat(self, parser):
+        """Add a --feat parsing argument"""
+
+        parser.add_argument("--feat", "--feature",
+                            help="Output features for a single specific "
+                                  "feature.")
+
+
+    def current_args(self, subparsers):
+        """Implementscurrent argparse subparser"""
+
+        parser = subparsers.add_parser("current",
+                                       formatter_class=argparse.RawTextHelpFormatter,
+                                       description="Output table in ReST "
+                                                   "compatible ASCII format "
+                                                   "with features for this "
+                                                   "machine's architecture")
+
+        self.parse_feat(parser)
+        parser.set_defaults(func=self.run_current)
+
+    def rest_args(self, subparsers):
+        """Implement rest argparse subparser"""
+
+        parser = subparsers.add_parser("rest",
+                                       formatter_class=argparse.RawTextHelpFormatter,
+                                       description="Output table(s) in ReST "
+                                                   "compatible ASCII format "
+                                                   "with features in ReST "
+                                                   "markup language. The "
+                                                   "output is affected by "
+                                                   "--arch or --feat/--feature"
+                                                   " flags.")
+
+        self.parse_arch(parser)
+        self.parse_feat(parser)
+        parser.set_defaults(func=self.run_rest)
+
+    def list_args(self, subparsers):
+        """Implement list argparse subparser"""
+
+        parser = subparsers.add_parser("list",
+                                       formatter_class=argparse.RawTextHelpFormatter,
+                                       description="List features for this "
+                                                   "machine's architecture, "
+                                                   "using an easier to parse "
+                                                   "format. The output is "
+                                                   "affected by --arch flag.")
+
+        self.parse_arch(parser)
+        self.parse_feat(parser)
+        parser.set_defaults(func=self.run_list)
+
+    def validate_args(self, subparsers):
+        """Implement validate argparse subparser"""
+
+        parser = subparsers.add_parser("validate",
+                                       formatter_class=argparse.RawTextHelpFormatter,
+                                       description="Validate the contents of "
+                                                   "the files under "
+                                                   f"{DEFAULT_DIR}.")
+
+        parser.set_defaults(func=self.run_parser)
+
+    def parser(self):
+        """
+        Create an arparse with common options and several subparsers
+        """
+        parser = argparse.ArgumentParser(formatter_class=argparse.RawTextHelpFormatter)
+
+        parser.add_argument("-d", "--debug", action="count", default=0,
+                            help="Put the script in verbose mode, useful for "
+                                 "debugging. Can be called multiple times, to "
+                                 "increase verbosity.")
+
+        parser.add_argument("--directory", "--dir", default=DEFAULT_DIR,
+                            help="Changes the location of the Feature files. "
+                                 f"By default, it uses the {DEFAULT_DIR} "
+                                 "directory.")
+
+        parser.add_argument("--enable-fname", action="store_true",
+                            help="Prints the file name of the feature files. "
+                                 "This can be used in order to track "
+                                 "dependencies during documentation build.")
+
+        subparsers = parser.add_subparsers()
+
+        self.current_args(subparsers)
+        self.rest_args(subparsers)
+        self.list_args(subparsers)
+        self.validate_args(subparsers)
+
+        args = parser.parse_args()
+
+        return args
+
+
+def main():
+    """Main program"""
+
+    feat = GetFeature()
+
+    args = feat.parser()
+
+    if "func" in args:
+        args.func(args)
+    else:
+        sys.exit(f"Please specify a valid command for {sys.argv[0]}")
+
+
+# Call main method
+if __name__ == "__main__":
+    main()