SPL: FIT: refactor FDT loading

Currently the SPL FIT loader uses the spl_fit_select_fdt() function to
find the offset to the right DTB within the FIT image.
For this it iterates over all subnodes of the /configuration node in
the FIT tree and compares all "description" strings therein using a
board specific matching function.
If that finds a match, it uses the string in the "fdt" property of that
subnode to locate the matching subnode in the /images node, which points
to the DTB data.
Now this works very well, but is quite specific to cover this particular
use case. To open up the door for a more generic usage, let's split this
function into:
1) a function that just returns the node offset for the matching
   configuration node (spl_fit_find_config_node())
2) a function that returns the image data any given property in a given
   configuration node points to, additionally using a given index into
   a possbile list of strings (spl_fit_select_index())
This allows us to replace the specific function above by asking for the
image the _first string of the "fdt" property_ in the matching
configuration subnode points to.

This patch introduces no functional changes, it just refactors the code
to allow reusing it later.

(diff is overly clever here and produces a hard-to-read patch, so I
recommend to throw a look at the result instead).

Signed-off-by: Andre Przywara <andre.przywara@arm.com>

1 files changed, 52 insertions, 31 deletions

diff --git a/common/spl/spl_fit.c b/common/spl/spl_fit.c
index aae556f97d..ba45e65a66 100644
--- a/common/spl/spl_fit.c
+++ b/common/spl/spl_fit.c
@@ -22,13 +22,11 @@ static ulong fdt_getprop_u32(const void *fdt, int node, const char *prop)
 	return fdt32_to_cpu(*cell);
 }
 
-static int spl_fit_select_fdt(const void *fdt, int images, int *fdt_offsetp)
+static int spl_fit_find_config_node(const void *fdt)
 {
-	const char *name, *fdt_name;
-	int conf, node, fdt_node;
-	int len;
+	const char *name;
+	int conf, node, len;
 
-	*fdt_offsetp = 0;
 	conf = fdt_path_offset(fdt, FIT_CONFS_PATH);
 	if (conf < 0) {
 		debug("%s: Cannot find /configurations node: %d\n", __func__,
@@ -50,39 +48,61 @@ static int spl_fit_select_fdt(const void *fdt, int images, int *fdt_offsetp)
 			continue;
 
 		debug("Selecting config '%s'", name);
-		fdt_name = fdt_getprop(fdt, node, FIT_FDT_PROP, &len);
-		if (!fdt_name) {
-			debug("%s: Cannot find fdt name property: %d\n",
-			      __func__, len);
-			return -EINVAL;
-		}
 
-		debug(", fdt '%s'\n", fdt_name);
-		fdt_node = fdt_subnode_offset(fdt, images, fdt_name);
-		if (fdt_node < 0) {
-			debug("%s: Cannot find fdt node '%s': %d\n",
-			      __func__, fdt_name, fdt_node);
-			return -EINVAL;
+		return node;
+	}
+
+	return -1;
+}
+
+static int spl_fit_select_index(const void *fit, int images, int *offsetp,
+				const char *type, int index)
+{
+	const char *name, *str;
+	int node, conf_node;
+	int len, i;
+
+	*offsetp = 0;
+	conf_node = spl_fit_find_config_node(fit);
+	if (conf_node < 0) {
+#ifdef CONFIG_SPL_LIBCOMMON_SUPPORT
+		printf("No matching DT out of these options:\n");
+		for (node = fdt_first_subnode(fit, conf_node);
+		     node >= 0;
+		     node = fdt_next_subnode(fit, node)) {
+			name = fdt_getprop(fit, node, "description", &len);
+			printf("   %s\n", name);
 		}
+#endif
+		return -ENOENT;
+	}
 
-		*fdt_offsetp = fdt_getprop_u32(fdt, fdt_node, "data-offset");
-		len = fdt_getprop_u32(fdt, fdt_node, "data-size");
-		debug("FIT: Selected '%s'\n", name);
+	name = fdt_getprop(fit, conf_node, type, &len);
+	if (!name) {
+		debug("cannot find property '%s': %d\n", type, len);
+		return -EINVAL;
+	}
 
-		return len;
+	str = name;
+	for (i = 0; i < index; i++) {
+		str = strchr(str, '\0') + 1;
+		if (!str || (str - name >= len)) {
+			debug("no string for index %d\n", index);
+			return -E2BIG;
+		}
 	}
 
-#ifdef CONFIG_SPL_LIBCOMMON_SUPPORT
-	printf("No matching DT out of these options:\n");
-	for (node = fdt_first_subnode(fdt, conf);
-	     node >= 0;
-	     node = fdt_next_subnode(fdt, node)) {
-		name = fdt_getprop(fdt, node, "description", &len);
-		printf("   %s\n", name);
+	debug("%s: '%s'\n", type, str);
+	node = fdt_subnode_offset(fit, images, str);
+	if (node < 0) {
+		debug("cannot find image node '%s': %d\n", str, node);
+		return -EINVAL;
 	}
-#endif
 
-	return -ENOENT;
+	*offsetp = fdt_getprop_u32(fit, node, "data-offset");
+	len = fdt_getprop_u32(fit, node, "data-size");
+
+	return len;
 }
 
 static int get_aligned_image_offset(struct spl_load_info *info, int offset)
@@ -218,7 +238,8 @@ int spl_load_simple_fit(struct spl_image_info *spl_image,
 	memcpy(dst, src, data_size);
 
 	/* Figure out which device tree the board wants to use */
-	fdt_len = spl_fit_select_fdt(fit, images, &fdt_offset);
+	fdt_len = spl_fit_select_index(fit, images, &fdt_offset,
+				       FIT_FDT_PROP, 0);
 	if (fdt_len < 0)
 		return fdt_len;