[PATCH v2 3/6] Add fdtget utility to read property values from device tree
David Gibson
david at gibson.dropbear.id.au
Thu Sep 8 15:25:47 EST 2011
On Wed, Sep 07, 2011 at 12:54:17PM -0700, Simon Glass wrote:
> 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>][<format>] Type of data
> -h Print this help
>
> <type> One character (s=string, i=int, u=unsigned, b=byte)
> <format> Optional format character (x=hex)
It is not terribly clear how these are combined.
Is there any way to make these more closely resemble printf() style
format specifiers?
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
> Changes in v2:
> - Separate arguments for node and property
> - Merge two related commits into this one
> - Use structure for storing display options
> - Remove use of getopt_long()
>
> .gitignore | 1 +
> Makefile | 4 +
> Makefile.fdtget | 12 +++
> fdtget.c | 200 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 217 insertions(+), 0 deletions(-)
> create mode 100644 Makefile.fdtget
> create mode 100644 fdtget.c
>
> diff --git a/.gitignore b/.gitignore
> index ae7a46a..9f27f34 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -10,3 +10,4 @@ lex.yy.c
> /ftdump
> /convert-dtsv0
> /version_gen.h
> +/fdtget
> diff --git a/Makefile b/Makefile
> index 0baada5..3d460d7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -106,10 +106,12 @@ endef
> include Makefile.convert-dtsv0
> include Makefile.dtc
> include Makefile.ftdump
> +include Makefile.fdtget
>
> BIN += convert-dtsv0
> BIN += dtc
> BIN += ftdump
> +BIN += fdtget
>
> SCRIPTS = dtdiff
>
> @@ -120,6 +122,7 @@ ifneq ($(DEPTARGETS),)
> -include $(DTC_OBJS:%.o=%.d)
> -include $(CONVERT_OBJS:%.o=%.d)
> -include $(FTDUMP_OBJS:%.o=%.d)
> +-include $(FDTGET_OBJS:%.o=%.d)
> endif
>
>
> @@ -180,6 +183,7 @@ convert-dtsv0: $(CONVERT_OBJS)
>
> ftdump: $(FTDUMP_OBJS) $(LIBFDT_archive)
>
> +fdtget: $(FDTGET_OBJS) $(LIBFDT_archive)
>
> #
> # Testsuite rules
> diff --git a/Makefile.fdtget b/Makefile.fdtget
> new file mode 100644
> index 0000000..c1ab041
> --- /dev/null
> +++ b/Makefile.fdtget
> @@ -0,0 +1,12 @@
> +#
> +# This is not a complete Makefile.
> +# Instead, it is designed to be easily embeddable
> +# into other systems of Makefiles.
> +#
> +
> +FDTGET_SRCS = \
> + fdtget.c \
> + util.c \
> + utilfdt.c
> +
> +FDTGET_OBJS = $(FDTGET_SRCS:%.c=%.o)
> diff --git a/fdtget.c b/fdtget.c
> new file mode 100644
> index 0000000..4a94e99
> --- /dev/null
> +++ b/fdtget.c
> @@ -0,0 +1,200 @@
> +/*
> + * Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
> + * Distributed under the terms of the GNU General Public License v2
> + *
> + * is_printable_string from ftdump.c
> + * Contributed by Pantelis Antoniou <pantelis.antoniou AT gmail.com>
> + */
> +
> +#include <ctype.h>
> +#include <getopt.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +
> +#include <libfdt.h>
> +
> +#include "util.h"
> +#include "utilfdt.h"
> +
> +/* Holds information which controls our output and options */
> +struct display_info {
> + int type; /* data type (s/i/u/b or 0 for default) */
> + int format; /* data format (x or 0 for default) */
> +};
> +
> +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
> + */
> +static void show_data(struct display_info *disp, const char *data, int len)
> +{
> + int i, size;
> + const char *p = data, *s;
> + int value;
> + int is_string;
> +
> + /* no data, don't print */
> + if (len == 0)
> + return;
> +
> + is_string = (disp->type) == 's' ||
> + (!disp->type && util_is_printable_string(data, len));
> + if (is_string) {
> + for (s = data; s - data < len; s += strlen(s) + 1) {
> + if (s != data)
> + printf(" ");
> + printf("%s", (const char *)s);
> + }
> + return;
> + }
> + if (disp->type == 'i' || disp->type == 'u')
> + size = 4;
> + else if (disp->type == 'b')
> + size = 1;
> + else
> + size = (len % 4) == 0 ? 4 : 1;
> + for (i = 0; i < len; i += size, p += size) {
> + if (i)
> + printf(" ");
> + value = size == 4 ? fdt32_to_cpu(*(const uint32_t *)p) :
> + *(const unsigned char *)p;
> + printf(disp->format == 'x' ? "%x" : "%d", value);
> + }
> +}
> +
> +/**
> + * Show the data for a given node (and perhaps property) according to the
> + * display option provided.
"and perhaps property"? AFAICT this will SEGV if property is NULL.
> + * @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) {
> + show_data(disp, value, len);
> + 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 = util_read_fdt(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>][<format>]\tType of data\n"
> + "\t-h\t\tPrint this help\n\n"
> + "\t<type>\t\tOne character (s=string, i=int, u=unsigned, b=byte)\n"
> + "\t<format>\tOptional format character (x=hex)\n";
> +
> +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;
> +
> + memset(&disp, '\0', sizeof(disp));
> + for (;;) {
> + int c = getopt(argc, argv, "ht:");
> + if (c == -1)
> + break;
> +
> + switch (c) {
> + case 'h':
> + case '?':
> + usage("");
> +
> + case 't':
> + if (utilfdt_decode_type(optarg, &disp.type,
> + &disp.format))
> + 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;
> +}
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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