discover/grub2: expose a struct for grub2 file references

Currently, we have struct grub2_resource_info to keep references to boot
payloads that may be returned in boot options, and be (conditionally)
resolved by the parser.

We'd also like to use the same semantics for other file references in
the grub2 parser, for arbitrary usage in scripts - where files are
also referenced by a path and an optional device.

To do this, this change moves struct grub2_resource_info to grub2.h, and
renames to struct grub2_file. Future changes will use this for
script-internal file handling.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

discover/grub2/grub2.c

@@ -33,17 +33,12 @@ static const char *const grub2_conf_files[] = {
 	NULL
 };
 
-struct grub2_resource_info {
-	char *root;
-	char *path;
-};
-
 /* we use slightly different resources for grub2 */
 struct resource *create_grub2_resource(struct discover_boot_option *opt,
 		struct discover_device *orig_device,
 		const char *root, const char *path)
 {
-	struct grub2_resource_info *info;
+	struct grub2_file *file;
 	struct resource *res;
 
 	if (strstr(path, "://")) {
@@ -55,13 +50,12 @@ struct resource *create_grub2_resource(struct discover_boot_option *opt,
 	res = talloc(opt, struct resource);
 
 	if (root) {
-		info = talloc(res, struct grub2_resource_info);
-		talloc_reference(info, root);
-		info->root = talloc_strdup(info, root);
-		info->path = talloc_strdup(info, path);
+		file = talloc(res, struct grub2_file);
+		file->dev = talloc_strdup(file, root);
+		file->path = talloc_strdup(file, path);
 
 		res->resolved = false;
-		res->info = info;
+		res->info = file;
 
 	} else
 		resolve_resource_against_device(res, orig_device, path);
@@ -72,18 +66,18 @@ struct resource *create_grub2_resource(struct discover_boot_option *opt,
 bool resolve_grub2_resource(struct device_handler *handler,
 		struct resource *res)
 {
-	struct grub2_resource_info *info = res->info;
+	struct grub2_file *file = res->info;
 	struct discover_device *dev;
 
 	assert(!res->resolved);
 
-	dev = device_lookup_by_uuid(handler, info->root);
+	dev = device_lookup_by_uuid(handler, file->dev);
 
 	if (!dev)
 		return false;
 
-	resolve_resource_against_device(res, dev, info->path);
-	talloc_free(info);
+	resolve_resource_against_device(res, dev, file->path);
+	talloc_free(file);
 
 	return true;
 }

discover/grub2/grub2.h

@@ -107,6 +107,14 @@ struct grub2_parser {
 	bool			inter_word;
 };
 
+/* References to files in grub2 consist of an optional device and a path
+ * (specified here by UUID). If the dev is unspecified, we fall back to a
+ * default - usually the 'root' environment variable. */
+struct grub2_file {
+	char *dev;
+	char *path;
+};
+
 /* type for builtin functions */
 typedef int (*grub2_function)(struct grub2_script *script, void *data,
 				int argc, char *argv[]);