[PATCH RFC v3 3/9] fdt-select-board: Add test tool for selecting dtbs based on board-id

[Elliot Berman]

Introduce a tool which scores devicetrees based on their board-id and a
supplied reference devicetree. This mechanism would be most similar to
an proposal to EBBR where firmware provides a reference devicetree which
contains the actual board identifier values, and an OS loader can
choose to replace (or overlay) the firmware-provided devicetree.

Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
 scripts/dtc/.gitignore         |   1 +
 scripts/dtc/Makefile           |   3 +-
 scripts/dtc/fdt-select-board.c | 126 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 129 insertions(+), 1 deletion(-)

diff --git a/scripts/dtc/.gitignore b/scripts/dtc/.gitignore
index e0b5c1d2464a..7f6d5202c0ba 100644
--- a/scripts/dtc/.gitignore
+++ b/scripts/dtc/.gitignore
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 /dtc
 /fdtoverlay
+/fdt-select-board
diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index 4d32b9497da9..a331f07091b3 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -2,7 +2,7 @@
 # scripts/dtc makefile
 
 # *** Also keep .gitignore in sync when changing ***
-hostprogs-always-$(CONFIG_DTC)		+= dtc fdtoverlay
+hostprogs-always-$(CONFIG_DTC)		+= dtc fdtoverlay fdt-select-board
 hostprogs-always-$(CHECK_DT_BINDING)	+= dtc
 
 dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
@@ -14,6 +14,7 @@ dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
 libfdt-objs	:= fdt.o fdt_ro.o fdt_wip.o fdt_sw.o fdt_rw.o fdt_strerror.o fdt_empty_tree.o fdt_addresses.o fdt_overlay.o
 libfdt		= $(addprefix libfdt/,$(libfdt-objs))
 fdtoverlay-objs	:= $(libfdt) fdtoverlay.o util.o
+fdt-select-board-objs := $(libfdt) fdt-select-board.o util.o
 
 # Source files need to get at the userspace version of libfdt_env.h to compile
 HOST_EXTRACFLAGS += -I $(srctree)/$(src)/libfdt
diff --git a/scripts/dtc/fdt-select-board.c b/scripts/dtc/fdt-select-board.c
new file mode 100644
index 000000000000..a7f3dc715ed1
--- /dev/null
+++ b/scripts/dtc/fdt-select-board.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+#include <ctype.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+#include <libfdt.h>
+
+#include "util.h"
+
+static const char usage_synopsis[] =
+	"find the best matching device tree from a reference board\n"
+	"	fdt-select-board <options> [<candidate.dtb>]\n"
+	"\n";
+static const char usage_short_opts[] = "r:av" USAGE_COMMON_SHORT_OPTS;
+static const struct option usage_long_opts[] = {
+	{"reference", required_argument, NULL, 'r'},
+	{"verbose",	    no_argument, NULL, 'v'},
+	{"all",		    no_argument, NULL, 'a'},
+	USAGE_COMMON_LONG_OPTS
+};
+
+static const char * const usage_opts_help[] = {
+	"Reference DTB",
+	"Verbose messages",
+	"List all matches",
+	USAGE_COMMON_OPTS_HELP
+};
+
+int verbose = 0;
+
+struct context {
+	const void *fdt;
+	int node;
+};
+
+static const void *get_board_id(void *ctx, const char *name, int *datalen)
+{
+	struct context *c = ctx;
+
+	return fdt_getprop(c->fdt, c->node, name, datalen);
+}
+
+int main(int argc, char *argv[])
+{
+	int opt;
+	char *input_filename = NULL;
+	const void *fdt;
+	const void *ref;
+	int ref_node;
+	int max_score = -1;
+	const char *best_match = NULL;
+	struct context ctx;
+	int all = 0;
+
+	while ((opt = util_getopt_long()) != EOF) {
+		switch (opt) {
+		case_USAGE_COMMON_FLAGS
+
+		case 'a':
+			all = 1;
+			break;
+		case 'r':
+			input_filename = optarg;
+			break;
+		case 'v':
+			verbose = 1;
+			break;
+		}
+	}
+
+	if (!input_filename)
+		usage("missing reference file");
+
+	argv += optind;
+	argc -= optind;
+
+	if (argc <= 0)
+		usage("missing candidate dtbs");
+
+	ref = utilfdt_read(input_filename, NULL);
+	if (!ref) {
+		fprintf(stderr, "failed to read reference %s\n", input_filename);
+		return -1;
+	}
+
+	ref_node = fdt_path_offset(ref, "/board-id");
+	if (ref_node < 0) {
+		fprintf(stderr, "reference blob doesn't have a board-id\n");
+		return -1;
+	}
+
+	ctx.fdt = ref;
+	ctx.node = ref_node;
+
+	for (; argc > 0; --argc, ++argv) {
+		int score;
+
+		fdt = utilfdt_read(*argv, NULL);
+		if (!fdt) {
+			fprintf(stderr, "failed to read %s\n", *argv);
+			return -1;
+		}
+
+		score = fdt_board_id_score(fdt, get_board_id, &ctx);
+		if (verbose || (score > 0 && all))
+			printf("%s: %d\n", *argv, score);
+
+		if (score > max_score) {
+			max_score = score;
+			best_match = *argv;
+		}
+
+		free(fdt);
+	}
+
+	if (best_match && !all)
+		printf("%s\n", best_match);
+
+	return 0;
+}

-- 
2.34.1