1 files changed, 117 insertions, 0 deletions
diff --git a/lib/efi_loader/efi_fdt.c b/lib/efi_loader/efi_fdt.c
new file mode 100644
index 00000000000..86ba00c2bdd
--- /dev/null
+++ b/lib/efi_loader/efi_fdt.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Bootmethod for distro boot via EFI
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#include <efi_loader.h>
+#include <env.h>
+#include <errno.h>
+#include <log.h>
+#include <string.h>
+#include <vsprintf.h>
+
+/**
+ * distro_efi_get_fdt_name() - get the filename for reading the .dtb file
+ *
+ * @fname:	buffer for filename
+ * @size:	buffer size
+ * @seq:	sequence number, to cycle through options (0=first)
+ *
+ * Returns:
+ * 0 on success,
+ * -ENOENT if the "fdtfile" env var does not exist,
+ * -EINVAL if there are no more options,
+ * -EALREADY if the control FDT should be used
+ */
+int efi_get_distro_fdt_name(char *fname, int size, int seq)
+{
+	const char *fdt_fname;
+	const char *prefix;
+
+	/* select the prefix */
+	switch (seq) {
+	case 0:
+		/* this is the default */
+		prefix = "/dtb";
+		break;
+	case 1:
+		prefix = "";
+		break;
+	case 2:
+		prefix = "/dtb/current";
+		break;
+	default:
+		return log_msg_ret("pref", -EINVAL);
+	}
+
+	fdt_fname = env_get("fdtfile");
+	if (fdt_fname) {
+		snprintf(fname, size, "%s/%s", prefix, fdt_fname);
+		log_debug("Using device tree: %s\n", fname);
+	} else if (IS_ENABLED(CONFIG_OF_HAS_PRIOR_STAGE)) {
+		strcpy(fname, "<prior>");
+		return log_msg_ret("pref", -EALREADY);
+	/* Use this fallback only for 32-bit ARM */
+	} else if (IS_ENABLED(CONFIG_ARM) && !IS_ENABLED(CONFIG_ARM64)) {
+		const char *soc = env_get("soc");
+		const char *board = env_get("board");
+		const char *boardver = env_get("boardver");
+
+		/* cf the code in label_boot() which seems very complex */
+		snprintf(fname, size, "%s/%s%s%s%s.dtb", prefix,
+			 soc ? soc : "", soc ? "-" : "", board ? board : "",
+			 boardver ? boardver : "");
+		log_debug("Using default device tree: %s\n", fname);
+	} else {
+		return log_msg_ret("env", -ENOENT);
+	}
+
+	return 0;
+}
+
+/**
+ * efi_load_distro_fdt() - load distro device-tree
+ *
+ * @fdt:	on return device-tree, must be freed via efi_free_pages()
+ * @fdt_size:	buffer size
+ */
+void efi_load_distro_fdt(void **fdt, efi_uintn_t *fdt_size)
+{
+	struct efi_device_path *rem, *dp;
+	efi_status_t  ret;
+	efi_handle_t device;
+
+	*fdt = NULL;
+
+	dp = efi_get_dp_from_boot(NULL);
+	if (!dp)
+		return;
+	device = efi_dp_find_obj(dp, NULL, &rem);
+	ret = efi_search_protocol(device, &efi_simple_file_system_protocol_guid,
+				  NULL);
+	if (ret != EFI_SUCCESS)
+		goto err;
+	memcpy(rem, &END, sizeof(END));
+
+	/* try the various available names */
+	for (int seq = 0; ; ++seq) {
+		struct efi_device_path *file;
+		char buf[255];
+
+		if (efi_get_distro_fdt_name(buf, sizeof(buf), seq))
+			break;
+		file = efi_dp_from_file(dp, buf);
+		if (!file)
+			break;
+		ret = efi_load_image_from_path(true, file, fdt, fdt_size);
+		efi_free_pool(file);
+		if (ret == EFI_SUCCESS)
+			break;
+	}
+
+err:
+	efi_free_pool(dp);
+}