docs: Kconfig/Makefile: add a check for broken ABI files

The files under Documentation/ABI should follow the syntax
as defined at Documentation/ABI/README.

Allow checking if they're following the syntax by running
the ABI parser script on COMPILE_TEST.

With that, when there's a problem with a file under
Documentation/ABI, it would produce a warning like:

	Warning: file ./Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats#14:
		What '/sys/bus/pci/devices/<dev>/aer_stats/aer_rootport_total_err_cor' doesn't have a description
	Warning: file ./Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats#21:
		What '/sys/bus/pci/devices/<dev>/aer_stats/aer_rootport_total_err_fatal' doesn't have a description

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/57a38de85cb4b548857207cf1fc1bf1ee08613c9.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/Kconfig

@@ -10,4 +10,14 @@ config WARN_MISSING_DOCUMENTS
 
 	   If unsure, select 'N'.
 
+config WARN_ABI_ERRORS
+	bool "Warn if there are errors at ABI files"
+	depends on COMPILE_TEST
+	help
+	   The files under Documentation/ABI should follow what's
+	   described at Documentation/ABI/README. Yet, as they're manually
+	   written, it would be possible that some of those files would
+	   have errors that would break them for being parsed by
+	   scripts/get_abi.pl. Add a check to verify them.
 
+	   If unsure, select 'N'.

Documentation/Makefile

@@ -10,6 +10,11 @@ ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
 $(shell $(srctree)/scripts/documentation-file-ref-check --warn)
 endif
 
+# Check for broken ABI files
+ifeq ($(CONFIG_WARN_ABI_ERRORS),y)
+$(shell $(srctree)/scripts/get_abi.pl validate --dir $(srctree)/Documentation/ABI)
+endif
+
 # You can set these variables from the command line.
 SPHINXBUILD   = sphinx-build
 SPHINXOPTS    =

lib/Kconfig.debug

@@ -2446,4 +2446,6 @@ config HYPERV_TESTING
 
 endmenu # "Kernel Testing and Coverage"
 
+source "Documentation/Kconfig"
+
 endmenu # Kernel hacking

scripts/get_abi.pl

@@ -50,7 +50,15 @@
 sub parse_error($$$$) {
 	my ($file, $ln, $msg, $data) = @_;
 
-	print STDERR "file $file#$ln: $msg at\n\t$data";
+	$data =~ s/\s+$/\n/;
+
+	print STDERR "Warning: file $file#$ln:\n\t$msg";
+
+	if ($data ne "") {
+		print STDERR ". Line\n\t\t$data";
+	} else {
+	    print STDERR "\n";
+	}
 }
 
 #
@@ -110,7 +118,7 @@ sub parse_abi {
 
 			# Invalid, but it is a common mistake
 			if ($new_tag eq "where") {
-				parse_error($file, $ln, "tag 'Where' is invalid. Should be 'What:' instead", $_);
+				parse_error($file, $ln, "tag 'Where' is invalid. Should be 'What:' instead", "");
 				$new_tag = "what";
 			}
 
@@ -225,7 +233,7 @@ sub parse_abi {
 		}
 
 		# Everything else is error
-		parse_error($file, $ln, "Unexpected line:", $_);
+		parse_error($file, $ln, "Unexpected content", $_);
 	}
 	$data{$nametag}->{description} =~ s/^\n+// if ($data{$nametag}->{description});
 	if ($what) {