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>
diff --git a/fdtget.c b/fdtget.c
new file mode 100644
index 0000000..48ab615
--- /dev/null
+++ b/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;
+}