Add fdtget utility to read property values from a device tree

This simply utility makes it easy for scripts to read values from the device
tree. It is written in C and uses the same libfdt as the rest of the dtc
package.

What is it for:
- Reading fdt values from scripts
- Extracting fdt information within build systems
- Looking at particular values without having to dump the entire tree

To use it, specify the fdt binary file on command line followed by a list of
node, property pairs. The utility then looks up each node, finds the property
and displays the value.

Each value is printed on a new line.

fdtget tries to guess the type of each property based on its contents. This
is not always reliable, so you can use the -t option to force fdtget to decode
the value as a string, or byte, etc.

To read from stdin, use - as the file.

Usage:
	fdtget <options> <dt file> [<node> <property>]...
Options:
	-t <type>	Type of data
	-h		Print this help

<type>	s=string, i=int, u=unsigned, x=hex
	Optional modifier prefix:
		hh or b=byte, h=2 byte, l=4 byte (default)

Signed-off-by: Simon Glass <sjg@chromium.org>

.gitignore

@@ -10,3 +10,4 @@ lex.yy.c
 /fdtdump
 /convert-dtsv0
 /version_gen.h
+/fdtget

Makefile

@@ -110,6 +110,7 @@ include Makefile.utils
 BIN += convert-dtsv0
 BIN += dtc
 BIN += fdtdump
+BIN += fdtget
 
 SCRIPTS = dtdiff
 
@@ -120,6 +121,7 @@ ifneq ($(DEPTARGETS),)
 -include $(DTC_OBJS:%.o=%.d)
 -include $(CONVERT_OBJS:%.o=%.d)
 -include $(FDTDUMP_OBJS:%.o=%.d)
+-include $(FDTGET_OBJS:%.o=%.d)
 endif
 
 
@@ -180,6 +182,8 @@ convert-dtsv0: $(CONVERT_OBJS)
 
 fdtdump:	$(FDTDUMP_OBJS)
 
+fdtget:	$(FDTGET_OBJS) $(LIBFDT_archive)
+
 
 #
 # Testsuite rules

Makefile.utils

@@ -8,3 +8,10 @@ FDTDUMP_SRCS = \
 	util.c
 
 FDTDUMP_OBJS = $(FDTDUMP_SRCS:%.c=%.o)
+
+
+FDTGET_SRCS = \
+	fdtget.c \
+	util.c
+
+FDTGET_OBJS = $(FDTGET_SRCS:%.c=%.o)

fdtget.c

@@ -0,0 +1,226 @@
+/*
+ * Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <ctype.h>
+#include <getopt.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <libfdt.h>
+
+#include "util.h"
+
+/* Holds information which controls our output and options */
+struct display_info {
+	int type;		/* data type (s/i/u/x or 0 for default) */
+	int size;		/* data size (1/2/4) */
+};
+
+static void report_error(const char *where, int err)
+{
+	fprintf(stderr, "Error at '%s': %s\n", where, fdt_strerror(err));
+}
+
+/**
+ * Displays data of a given length according to selected options
+ *
+ * If a specific data type is provided in disp, then this is used. Otherwise
+ * we try to guess the data type / size from the contents.
+ *
+ * @param disp		Display information / options
+ * @param data		Data to display
+ * @param len		Maximum length of buffer
+ * @return 0 if ok, -1 if data does not match format
+ */
+static int show_data(struct display_info *disp, const char *data, int len)
+{
+	int i, size;
+	const uint8_t *p = (const uint8_t *)data;
+	const char *s;
+	int value;
+	int is_string;
+	char fmt[3];
+
+	/* no data, don't print */
+	if (len == 0)
+		return 0;
+
+	is_string = (disp->type) == 's' ||
+		(!disp->type && util_is_printable_string(data, len));
+	if (is_string) {
+		if (data[len - 1] != '\0') {
+			fprintf(stderr, "Unterminated string\n");
+			return -1;
+		}
+		for (s = data; s - data < len; s += strlen(s) + 1) {
+			if (s != data)
+				printf(" ");
+			printf("%s", (const char *)s);
+		}
+		return 0;
+	}
+	size = disp->size;
+	if (size == -1)
+		size = (len % 4) == 0 ? 4 : 1;
+	else if (len % size) {
+		fprintf(stderr, "Property length must be a multiple of "
+				"selected data size\n");
+		return -1;
+	}
+	fmt[0] = '%';
+	fmt[1] = disp->type ? disp->type : 'd';
+	fmt[2] = '\0';
+	for (i = 0; i < len; i += size, p += size) {
+		if (i)
+			printf(" ");
+		value = size == 4 ? fdt32_to_cpu(*(const uint32_t *)p) :
+			size == 2 ? (*p << 8) | p[1] : *p;
+		printf(fmt, value);
+	}
+	return 0;
+}
+
+/**
+ * Show the data for a given node (and perhaps property) according to the
+ * display option provided.
+ *
+ * @param blob		FDT blob
+ * @param disp		Display information / options
+ * @param node		Node to display
+ * @param property	Name of property to display, or NULL if none
+ * @return 0 if ok, -ve on error
+ */
+static int show_data_for_item(const void *blob, struct display_info *disp,
+		int node, const char *property)
+{
+	const void *value = NULL;
+	int len, err = 0;
+
+	value = fdt_getprop(blob, node, property, &len);
+	if (value) {
+		if (show_data(disp, value, len))
+			err = -1;
+		else
+			printf("\n");
+	} else {
+		report_error(property, len);
+		err = -1;
+	}
+	return err;
+}
+
+/**
+ * Run the main fdtget operation, given a filename and valid arguments
+ *
+ * @param disp		Display information / options
+ * @param filename	Filename of blob file
+ * @param arg		List of arguments to process
+ * @param arg_count	Number of arguments
+ * @param return 0 if ok, -ve on error
+ */
+static int do_fdtget(struct display_info *disp, const char *filename,
+		     char **arg, int arg_count)
+{
+	char *blob;
+	int i, node;
+
+	blob = utilfdt_read(filename);
+	if (!blob)
+		return -1;
+
+	for (i = 0; i + 2 <= arg_count; i += 2) {
+		node = fdt_path_offset(blob, arg[0]);
+		if (node < 0) {
+			report_error(arg[0], node);
+			return -1;
+		}
+
+		if (show_data_for_item(blob, disp, node, arg[1]))
+			return -1;
+	}
+	return 0;
+}
+
+static const char *usage_msg =
+	"fdtget - read values from device tree\n"
+	"\n"
+	"Each value is printed on a new line.\n\n"
+	"Usage:\n"
+	"	fdtget <options> <dt file> [<node> <property>]...\n"
+	"Options:\n"
+	"\t-t <type>\tType of data\n"
+	"\t-h\t\tPrint this help\n\n"
+	USAGE_TYPE_MSG;
+
+static void usage(const char *msg)
+{
+	if (msg)
+		fprintf(stderr, "Error: %s\n\n", msg);
+
+	fprintf(stderr, "%s", usage_msg);
+	exit(2);
+}
+
+int main(int argc, char *argv[])
+{
+	char *filename = NULL;
+	struct display_info disp;
+
+	/* set defaults */
+	memset(&disp, '\0', sizeof(disp));
+	disp.size = -1;
+	for (;;) {
+		int c = getopt(argc, argv, "ht:");
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+		case '?':
+			usage(NULL);
+
+		case 't':
+			if (utilfdt_decode_type(optarg, &disp.type,
+					&disp.size))
+				usage("Invalid type string");
+			break;
+		}
+	}
+
+	if (optind < argc)
+		filename = argv[optind++];
+	if (!filename)
+		usage("Missing filename");
+
+	argv += optind;
+	argc -= optind;
+
+	/* Allow no arguments, and silently succeed */
+	if (!argc)
+		return 0;
+
+	/* Check for node, property arguments */
+	if (argc % 2)
+		usage("Must have an even number of arguments");
+
+	if (do_fdtget(&disp, filename, argv, argc))
+		return 1;
+	return 0;
+}

tests/fdtget-runtest.sh

@@ -0,0 +1,35 @@
+#! /bin/sh
+
+. ./tests.sh
+
+LOG="tmp.log.$$"
+EXPECT="tmp.expect.$$"
+
+rm -f $TMPFILE $LOG
+
+expect="$1"
+echo "$expect" >$EXPECT
+shift
+
+verbose_run_log "$LOG" $VALGRIND "$DTGET" "$@"
+ret="$?"
+
+if [ "$ret" -ne 0 -a "$expect" = "ERR" ]; then
+	PASS
+fi
+
+if [ "$ret" -gt 127 ]; then
+    signame=$(kill -l $[ret - 128])
+    FAIL "Killed by SIG$signame"
+fi
+
+diff $EXPECT $LOG
+ret="$?"
+
+rm -f $LOG $EXPECT
+
+if [ "$ret" -eq 0 ]; then
+	PASS
+else
+	FAIL
+fi

tests/run_tests.sh

@@ -83,6 +83,13 @@ asm_to_so_test () {
     run_wrap_test asm_to_so "$@"
 }
 
+run_fdtget_test () {
+    # run_fdtget_test name expected_output dtb_file args...
+    echo -n "$1:	"
+    shift
+    base_run_test sh fdtget-runtest.sh "$@"
+}
+
 tree1_tests () {
     TREE=$1
 
@@ -402,6 +409,37 @@ dtbs_equal_tests () {
     cmp_tests test_tree1.dtb $WRONG_TREE1
 }
 
+fdtget_tests () {
+    file=label01.dtb
+    $DTC -O dtb -o $file ${file%.dtb}.dts 2>/dev/null
+
+    # run_fdtget_test <test-name> <expected-result> <args>...
+    run_fdtget_test "Simple string" "MyBoardName" $file / model
+    run_fdtget_test "Multiple string i" "77 121 66 111 \
+97 114 100 78 97 109 101 0 77 121 66 111 97 114 100 70 97 109 105 \
+108 121 78 97 109 101 0" $file / compatible
+    run_fdtget_test "Multiple string s" "MyBoardName MyBoardFamilyName" \
+	-t s $file / compatible
+    run_fdtget_test "Integer" "32768" $file /cpus/PowerPC,970@1 d-cache-size
+    run_fdtget_test "Integer hex" "8000" -tx $file \
+	/cpus/PowerPC,970@1 d-cache-size
+    run_fdtget_test "Integer list" "61 62 63 0" -tbx $file \
+	/randomnode tricky1
+    run_fdtget_test "Byte list short" "a b c d de ea ad be ef" -tbx \
+	$file /randomnode blob
+
+    # Here the property size is not a multiple of 4 bytes, so it should fail
+    run_fdtget_test "Integer list invalid" ERR -tlx \
+	$file /randomnode mixed
+    run_fdtget_test "Integer list halfword" "6162 6300 1234 0 a 0 b 0 c" -thx \
+	$file /randomnode mixed
+    run_fdtget_test "Integer list byte" \
+	"61 62 63 0 12 34 0 0 0 a 0 0 0 b 0 0 0 c" -thhx \
+	$file /randomnode mixed
+    run_fdtget_test "Missing property" ERR -ts \
+	$file /randomnode doctor-who
+}
+
 utilfdt_tests () {
     run_test utilfdt_test
 }
@@ -421,7 +459,7 @@ while getopts "vt:m" ARG ; do
 done
 
 if [ -z "$TESTSETS" ]; then
-    TESTSETS="libfdt utilfdt dtc dtbs_equal"
+    TESTSETS="libfdt utilfdt dtc dtbs_equal fdtget"
 fi
 
 # Make sure we don't have stale blobs lying around
@@ -441,6 +479,9 @@ for set in $TESTSETS; do
 	"dtbs_equal")
 	    dtbs_equal_tests
 	    ;;
+	"fdtget")
+	    fdtget_tests
+	    ;;
     esac
 done
 

tests/tests.sh

@@ -11,6 +11,7 @@ FAIL () {
 }
 
 DTC=../dtc
+DTGET=../fdtget
 
 verbose_run () {
     if [ -z "$QUIET_TEST" ]; then

util.h

@@ -140,4 +140,14 @@ int utilfdt_write_err(const char *filename, const void *blob);
  */
 int utilfdt_decode_type(const char *fmt, int *type, int *size);
 
+/*
+ * This is a usage message fragment for the -t option. It is the format
+ * supported by utilfdt_decode_type.
+ */
+
+#define USAGE_TYPE_MSG \
+	"<type>\ts=string, i=int, u=unsigned, x=hex\n" \
+	"\tOptional modifier prefix:\n" \
+	"\t\thh or b=byte, h=2 byte, l=4 byte (default)\n";
+
 #endif /* _UTIL_H */