efi_loader: implement EFI_DEVICE_PATH_TO_TEXT_PROTOCOL

ConvertPathToText is implemented for
* type 4    - media device path
* subtype 4 - file path

This is the kind of device path we hand out for block devices.

All other cases may be implemented later.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
[agraf: fix whitespace]
Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_device_path_to_text.c

@@ -0,0 +1,67 @@
+/*
+ *  EFI device path interface
+ *
+ *  Copyright (c) 2017 Heinrich Schuchardt
+ *
+ *  SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#include <common.h>
+#include <efi_loader.h>
+
+#define MEDIA_DEVICE_PATH 4
+#define FILE_PATH_MEDIA_DEVICE_PATH 4
+
+const efi_guid_t efi_guid_device_path_to_text_protocol =
+		EFI_DEVICE_PATH_TO_TEXT_PROTOCOL_GUID;
+
+uint16_t *efi_convert_device_node_to_text(
+		struct efi_device_path_protocol *device_node,
+		bool display_only,
+		bool allow_shortcuts)
+{
+	EFI_ENTRY("%p, %d, %d", device_node, display_only, allow_shortcuts);
+
+	EFI_EXIT(EFI_UNSUPPORTED);
+	return NULL;
+}
+
+uint16_t *efi_convert_device_path_to_text(
+		struct efi_device_path_protocol *device_path,
+		bool display_only,
+		bool allow_shortcuts)
+{
+	EFI_ENTRY("%p, %d, %d", device_path, display_only, allow_shortcuts);
+
+	unsigned long buffer_size;
+	efi_status_t r;
+	uint16_t *buffer = NULL;
+
+	switch (device_path->type) {
+	case MEDIA_DEVICE_PATH:
+		switch (device_path->sub_type) {
+		case FILE_PATH_MEDIA_DEVICE_PATH:
+			buffer_size = device_path->length - 4;
+			r = efi_allocate_pool(EFI_ALLOCATE_ANY_PAGES,
+					      buffer_size, (void **) &buffer);
+			if (r == EFI_SUCCESS)
+				memcpy(buffer, device_path->data, buffer_size);
+			break;
+		}
+	}
+
+	if (buffer) {
+		EFI_EXIT(EFI_SUCCESS);
+	} else {
+		debug("type %d, subtype %d\n",
+		      device_path->type, device_path->sub_type);
+		EFI_EXIT(EFI_UNSUPPORTED);
+	}
+
+	return buffer;
+}
+
+const struct efi_device_path_to_text_protocol efi_device_path_to_text = {
+	.convert_device_node_to_text = efi_convert_device_node_to_text,
+	.convert_device_path_to_text = efi_convert_device_path_to_text,
+};