[PATCH] fdtgrep: Add option to reserve free space in the output FDT

[Simon Glass]

When producing a DTB from fdtgrep, there is no way to reserve extra
space so that more nodes/properties can be added at runtime without
growing totalsize first.

Add a -B/--pad option that appends a caller-specified number of free
bytes after the strings section and grows totalsize accordingly. The
padding is applied after fdt_pack(), so it is not reclaimed when -r is
used.

Suggested-by: Marek Vasut <marek.vasut at mailbox.org>
Signed-off-by: Simon Glass <sjg at chromium.org>
---

 tools/binman/btool/fdtgrep.py |  3 ++-
 tools/fdtgrep.c               | 31 ++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/tools/binman/btool/fdtgrep.py b/tools/binman/btool/fdtgrep.py
index 446b2f4144b..7b393241878 100644
--- a/tools/binman/btool/fdtgrep.py
+++ b/tools/binman/btool/fdtgrep.py
@@ -16,9 +16,10 @@ Output formats are:
 	dtb - device tree blob (sets -Hmt automatically)
 	bin - device tree fragment (may not be a valid .dtb)
 
-Options: -[haAc:b:C:defg:G:HIlLmn:N:o:O:p:P:rRsStTvhV]
+Options: -[haAB:c:b:C:defg:G:HIlLmn:N:o:O:p:P:rRsStTvhV]
   -a, --show-address                 Display address
   -A, --colour                       Show all nodes/tags, colour those that match
+  -B, --pad <arg>                    Append free space to the output FDT, for later growth
   -b, --include-node-with-prop <arg> Include contains containing property
   -c, --include-compat <arg>         Compatible nodes to include in grep
   -C, --exclude-compat <arg>         Compatible nodes to exclude in grep
diff --git a/tools/fdtgrep.c b/tools/fdtgrep.c
index b4c041070f5..83e3d0b9314 100644
--- a/tools/fdtgrep.c
+++ b/tools/fdtgrep.c
@@ -64,6 +64,7 @@ struct display_info {
 	int types_exc;		/* Mask of types that we exclude (FDT_IS...) */
 	int invert;		/* Invert polarity of match */
 	int props_up;		/* Imply properties up to supernodes */
+	int pad;		/* Free bytes to append after the strings section */
 	struct value_node *value_head;	/* List of values to match */
 	const char *output_fname;	/* Output filename */
 	FILE *fout;		/* File to write dts/dtb output */
@@ -913,6 +914,27 @@ static int do_fdtgrep(struct display_info *disp, const char *filename)
 			size = fdt_totalsize(fdt);
 		}
 
+		if (disp->pad) {
+			int new_size = fdt_totalsize(fdt) + disp->pad;
+			void *new_fdt = realloc(fdt, new_size);
+
+			if (!new_fdt) {
+				fprintf(stderr, "Out_of_memory\n");
+				ret = -1;
+				goto err;
+			}
+			fdt = new_fdt;
+			ret = fdt_open_into(fdt, fdt, new_size);
+			if (ret < 0) {
+				fprintf(stderr,
+					"Failed to expand FDT: %s\n",
+					fdt_strerror(ret));
+				goto err;
+			}
+			memset((char *)fdt + size, '\0', new_size - size);
+			size = new_size;
+		}
+
 		if ((size_t)size != fwrite(fdt, 1, size, disp->fout)) {
 			fprintf(stderr, "Write failure, %d bytes\n", size);
 			free(fdt);
@@ -965,11 +987,12 @@ static const char usage_synopsis[] =
 	case '?': usage("unknown option");
 
 static const char usage_short_opts[] =
-		"haAc:b:C:defg:G:HIlLmn:N:o:O:p:P:rRsStTuv"
+		"haAB:c:b:C:defg:G:HIlLmn:N:o:O:p:P:rRsStTuv"
 		USAGE_COMMON_SHORT_OPTS;
 static const struct option usage_long_opts[] = {
 	{"show-address",	no_argument, NULL, 'a'},
 	{"colour",		no_argument, NULL, 'A'},
+	{"pad",			a_argument, NULL, 'B'},
 	{"include-node-with-prop", a_argument, NULL, 'b'},
 	{"include-compat",	a_argument, NULL, 'c'},
 	{"exclude-compat",	a_argument, NULL, 'C'},
@@ -1002,6 +1025,7 @@ static const struct option usage_long_opts[] = {
 static const char * const usage_opts_help[] = {
 	"Display address",
 	"Show all nodes/tags, colour those that match",
+	"Append free space to the output FDT, for later growth",
 	"Include contains containing property",
 	"Compatible nodes to include in grep",
 	"Compatible nodes to exclude in grep",
@@ -1132,6 +1156,11 @@ static void scan_args(struct display_info *disp, int argc, char *argv[])
 		case 'A':
 			disp->all = 1;
 			break;
+		case 'B':
+			disp->pad = atoi(optarg);
+			if (disp->pad < 0)
+				usage("Padding must be non-negative");
+			break;
 		case 'b':
 			type = FDT_NODE_HAS_PROP;
 			break;
---
base-commit: 052988aa29bfd506d7ce207fbb3f5374a5dbecbb
branch: fdtgrep

-- 
2.43.0