mkimage: Support a load-only FIT

Support creation of a load-only FIT (where there is no OS), with a new
--load-only option. Allow FITs to be created without an OS image.

Update the auto-generated FIT description to make this clear.

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

doc/mkimage.1

@@ -476,6 +476,19 @@ the timestamp is assumed to have been set previously.
 This section documents the formats of the primary and secondary configuration
 options for each image type which supports them.
 .
+.TQ
+.B \-\-load\-only
+Permit creation of a load-only FIT.
+.IP
+Normally a FIT has an OS image included and mkimage expects this. With this
+option, a special FIT can be created which only has devicetrees. This can be
+loaded before the normal 'OS' devicetree. This option sets the load-only
+property in each generated configuration and allows the OS image to be missing.
+.
+.SH CONFIGURATION
+This section documents the formats of the primary and secondary configuration
+options for each image type which supports them.
+.
 .SS aisimage
 The primary configuration is a file containing a series of
 .I AIS

tools/fit_image.c

@@ -100,12 +100,14 @@ err_keydest:
 static int fit_calc_size(struct imgtool *itl)
 {
 	struct content_info *cont;
-	int size, total_size;
+	int size, total_size = 0;
 
-	size = imagetool_get_filesize(itl, itl->datafile);
-	if (size < 0)
-		return -1;
-	total_size = size;
+	if (itl->datafile) {
+		size = imagetool_get_filesize(itl, itl->datafile);
+		if (size < 0)
+			return -1;
+		total_size += size;
+	}
 
 	if (itl->fit_ramdisk) {
 		size = imagetool_get_filesize(itl, itl->fit_ramdisk);
@@ -285,29 +287,33 @@ static int fit_write_images(struct imgtool *itl, char *fdt)
 	fdt_begin_node(fdt, "images");
 
 	/* First the main image */
-	typename = genimg_get_type_short_name(itl->fit_image_type);
-	snprintf(str, sizeof(str), "%s-1", typename);
-	fdt_begin_node(fdt, str);
-	fdt_property_string(fdt, FIT_DESC_PROP, itl->imagename);
-	fdt_property_string(fdt, FIT_TYPE_PROP, typename);
-	fdt_property_string(fdt, FIT_ARCH_PROP,
-			    genimg_get_arch_short_name(itl->arch));
-	fdt_property_string(fdt, FIT_OS_PROP,
-			    genimg_get_os_short_name(itl->os));
-	fdt_property_string(fdt, FIT_COMP_PROP,
-			    genimg_get_comp_short_name(itl->comp));
-	fdt_property_u32(fdt, FIT_LOAD_PROP, itl->addr);
-	fdt_property_u32(fdt, FIT_ENTRY_PROP, itl->ep);
+	if (itl->datafile) {
+		typename = genimg_get_type_short_name(itl->fit_image_type);
+		snprintf(str, sizeof(str), "%s-1", typename);
+		fdt_begin_node(fdt, str);
+		fdt_property_string(fdt, FIT_DESC_PROP, itl->imagename);
+		fdt_property_string(fdt, FIT_TYPE_PROP, typename);
+		fdt_property_string(fdt, FIT_ARCH_PROP,
+				    genimg_get_arch_short_name(itl->arch));
+		fdt_property_string(fdt, FIT_OS_PROP,
+				    genimg_get_os_short_name(itl->os));
+		fdt_property_string(fdt, FIT_COMP_PROP,
+				    genimg_get_comp_short_name(itl->comp));
+		fdt_property_u32(fdt, FIT_LOAD_PROP, itl->addr);
+		fdt_property_u32(fdt, FIT_ENTRY_PROP, itl->ep);
 
-	/*
-	 * Put data last since it is large. SPL may only load the first part
-	 * of the DT, so this way it can access all the above fields.
-	 */
-	ret = fdt_property_file(itl, fdt, itl->datafile, NULL);
-	if (ret)
-		return ret;
-	fit_add_hash_or_sign(itl, fdt, true);
-	fdt_end_node(fdt);
+		/*
+		 * Put data last since it is large. SPL may only load the first
+		 * part of the DT, so this way it can access all the above
+		 * fields. If the FIT is converted to use external data, then
+		 * there is no benefit here, but also no loss.
+		 */
+		ret = fdt_property_file(itl, fdt, itl->datafile, NULL);
+		if (ret)
+			return ret;
+		fit_add_hash_or_sign(itl, fdt, true);
+		fdt_end_node(fdt);
+	}
 
 	/* Now the device tree files if available */
 	upto = 0;
@@ -406,6 +412,8 @@ static void fit_write_configs(struct imgtool *itl, char *fdt)
 
 		snprintf(str, sizeof(str), FIT_FDT_PROP "-%d", upto);
 		fdt_property_string(fdt, FIT_FDT_PROP, str);
+		if (itl->load_only)
+			fdt_property(fdt, FIT_LOAD_ONLY_PROP, NULL, 0);
 		if (cont->compat)
 			fdt_property(fdt, FIT_COMPATIBLE_PROP, cont->compat,
 				     cont->compat_len);
@@ -433,16 +441,26 @@ static void fit_write_configs(struct imgtool *itl, char *fdt)
 
 static int fit_build_fdt(struct imgtool *itl, char *fdt, int size)
 {
+	const struct content_info *cont;
+	bool has_fdt;
 	int ret;
 
+	has_fdt = false;
+	for (cont = itl->content_head; cont; cont = cont->next) {
+		if (cont->type == IH_TYPE_FLATDT) {
+			has_fdt = true;
+			break;
+		}
+	}
+
 	ret = fdt_create(fdt, size);
 	if (ret)
 		return ret;
 	fdt_finish_reservemap(fdt);
 	fdt_begin_node(fdt, "");
-	fdt_property_strf(fdt, FIT_DESC_PROP,
-			  "%s image with one or more FDT blobs",
-			  genimg_get_type_name(itl->fit_image_type));
+	fdt_property_strf(fdt, FIT_DESC_PROP, "%s image%s",
+			  genimg_get_type_name(itl->fit_image_type),
+			  has_fdt ? " with one or more FDT blobs" : "");
 	fdt_property_strf(fdt, "creator", "U-Boot mkimage %s", PLAIN_VERSION);
 	fdt_property_u32(fdt, "#address-cells", 1);
 	ret = fit_write_images(itl, fdt);

tools/imagetool.h

@@ -111,6 +111,7 @@ struct imgtool {
 	const char *engine_id;	/* Engine to use for signing */
 	bool reset_timestamp;	/* Reset the timestamp on an existing image */
 	struct image_summary summary;	/* results of signing process */
+	bool load_only;		/* true to create a load-only FIT */
 };
 
 /** struct imgtool_funcs - image-type-specific variables and callbacks */

tools/mkimage.c

@@ -155,6 +155,10 @@ static int add_content(struct imgtool *itl, int type, const char *fname)
 static const char optstring[] =
 	"a:A:b:B:c:C:d:D:e:Ef:Fg:G:i:k:K:ln:N:o:O:p:qrR:stT:vVx";
 
+enum {
+	OPT_LOAD_ONLY	= 1,
+};
+
 static const struct option longopts[] = {
 	{ "load-address", required_argument, NULL, 'a' },
 	{ "architecture", required_argument, NULL, 'A' },
@@ -189,6 +193,7 @@ static const struct option longopts[] = {
 	{ "verbose", no_argument, NULL, 'v' },
 	{ "version", no_argument, NULL, 'V' },
 	{ "xip", no_argument, NULL, 'x' },
+	{ "load-only", no_argument, NULL, OPT_LOAD_ONLY },
 	{ /* sentinel */ },
 };
 
@@ -360,6 +365,9 @@ static int process_args(struct imgtool *itl, int argc, char **argv)
 		case 'x':
 			itl->xflag++;
 			break;
+		case OPT_LOAD_ONLY:
+			itl->load_only = true;
+			break;
 		default:
 			return usage(itl, "Invalid option");
 		}
@@ -390,7 +398,7 @@ static int process_args(struct imgtool *itl, int argc, char **argv)
 		/* For auto-FIT, datafile has to be provided with -d */
 		if (!itl->auto_fit)
 			itl->datafile = datafile;
-		else if (!itl->datafile)
+		else if (!itl->datafile && type != IH_TYPE_FLATDT)
 			return usage(itl,
 				     "Missing data file for auto-FIT (use -d)");
 	} else if (itl->lflag || type != IH_TYPE_INVALID) {