--- zzzz-none-000/linux-5.15.111/drivers/firmware/efi/libstub/file.c	2023-05-11 14:00:40.000000000 +0000
+++ puma7-atom-6670-761/linux-5.15.111/drivers/firmware/efi/libstub/file.c	2024-02-07 10:22:41.000000000 +0000
@@ -37,7 +37,8 @@
 static efi_status_t efi_open_file(efi_file_protocol_t *volume,
 				  struct finfo *fi,
 				  efi_file_protocol_t **handle,
-				  unsigned long *file_size)
+				  unsigned long *file_size,
+				  bool silent)
 {
 	efi_guid_t info_guid = EFI_FILE_INFO_ID;
 	efi_file_protocol_t *fh;
@@ -46,14 +47,16 @@
 
 	status = volume->open(volume, &fh, fi->filename, EFI_FILE_MODE_READ, 0);
 	if (status != EFI_SUCCESS) {
-		efi_err("Failed to open file: %ls\n", fi->filename);
+		if (!silent)
+			efi_err("Failed to open file: %ls\n", fi->filename);
 		return status;
 	}
 
 	info_sz = sizeof(struct finfo);
 	status = fh->get_info(fh, &info_guid, &info_sz, fi);
 	if (status != EFI_SUCCESS) {
-		efi_err("Failed to get file info\n");
+		if (!silent)
+			efi_err("Failed to get file info\n");
 		fh->close(fh);
 		return status;
 	}
@@ -176,7 +179,7 @@
 				return status;
 		}
 
-		status = efi_open_file(volume, &fi, &file, &size);
+		status = efi_open_file(volume, &fi, &file, &size, false);
 		if (status != EFI_SUCCESS)
 			goto err_close_volume;
 
@@ -248,3 +251,126 @@
 	efi_free(alloc_size, alloc_addr);
 	return status;
 }
+
+static efi_status_t avm_build_dtb_name_for(int hwrev, int hwsubrev,
+					   efi_char16_t *path, size_t size)
+{
+	char apath[40];
+	int len;
+
+	len = snprintf(apath, sizeof(apath), "efi\\boot\\Fritz_Box_HW%u-%u.dtb",
+		       hwrev, hwsubrev);
+
+	if (len >= min(size, sizeof(apath)))
+		return EFI_BUFFER_TOO_SMALL;
+
+	for (; len >= 0; --len)
+		path[len] = apath[len];
+
+	return EFI_SUCCESS;
+}
+
+/*
+ * Check the efi/boot folder for a suitable DTB and load it.
+ *
+ * If no DTB filename matches the HW-Subrevision, it will look up DTBs for
+ * older subrevisions. If none is found, the function fails.
+ */
+efi_status_t avm_get_dtb_setup_data(efi_loaded_image_t *image,
+				    struct setup_data **dtb_setup_data)
+{
+	unsigned long dtb_size, size, efi_varsiz;
+	efi_file_protocol_t *volume, *dtb_file;
+	struct setup_data *setup_data;
+	efi_status_t status;
+	int hwrev, hwsubrev;
+	struct finfo fi;
+	u8 efi_var[16];
+	ssize_t len;
+	__u8 *data;
+
+	if (!dtb_setup_data)
+		return EFI_INVALID_PARAMETER;
+
+	efi_varsiz = sizeof(efi_var) - 1;
+	status = get_efi_var(L"HWRevision", &EFI_AVM_VARIABLE_GUID, NULL,
+			     &efi_varsiz, efi_var);
+	if (status != EFI_SUCCESS) {
+		efi_err("Error reading EFI variable: %d\n", status);
+		return status;
+	}
+
+	efi_var[efi_varsiz] = '\0';
+	hwrev = simple_strtol(efi_var, NULL, 10);
+
+	efi_varsiz = sizeof(efi_var) - 1;
+	status = get_efi_var(L"HWSubRevision", &EFI_AVM_VARIABLE_GUID, NULL,
+			     &efi_varsiz, efi_var);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	efi_var[efi_varsiz] = '\0';
+	hwsubrev = simple_strtol(efi_var, NULL, 10);
+
+	status = efi_open_volume(image, &volume);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	for (;;) {
+		status = avm_build_dtb_name_for(hwrev, hwsubrev, fi.filename,
+						ARRAY_SIZE(fi.filename));
+		if (status != EFI_SUCCESS)
+			return status;
+
+		status = efi_open_file(volume, &fi, &dtb_file, &dtb_size, true);
+		if (status == EFI_SUCCESS)
+			break;
+
+		if (hwsubrev-- == 0) {
+			efi_puts("No DTB found\n");
+			return EFI_NOT_FOUND;
+		}
+	}
+
+	efi_puts("DTB found: ");
+	efi_char16_puts(fi.filename);
+	efi_puts("\n");
+
+	status = efi_allocate_pages(dtb_size + sizeof(struct setup_data),
+				    (unsigned long *)&setup_data, ULONG_MAX);
+	if (status != EFI_SUCCESS) {
+		efi_err("Failed to alloc pages for setup_data: %d\n", status);
+		goto close_dtb_file;
+	}
+
+	data = setup_data->data;
+	size = dtb_size;
+	while (size) {
+		unsigned long chunksize = ULONG_MAX;
+
+		if (IS_ENABLED(CONFIG_X86) && !efi_nochunk)
+			chunksize = EFI_READ_CHUNK_SIZE;
+
+		status = dtb_file->read(dtb_file, &chunksize, data);
+		if (status != EFI_SUCCESS) {
+			efi_err("Failed to read dtb file: %d\n", status);
+			goto free_setup_data;
+		}
+		data += chunksize;
+		size -= chunksize;
+	}
+
+	dtb_file->close(dtb_file);
+
+	setup_data->type = SETUP_DTB;
+	setup_data->len = (__u32)dtb_size;
+	*dtb_setup_data = setup_data;
+
+	return status;
+
+free_setup_data:
+	efi_free(dtb_size + sizeof(struct setup_data), (unsigned long)setup_data);
+close_dtb_file:
+	dtb_file->close(dtb_file);
+	return status;
+}