efi_loader: disk: add efi_disk_is_removable()

This helper function will be used to determine if the device is
removable media, initially for handling a short-path loading.
Signed-off-by: NAKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>

include/efi_loader.h

@@ -663,6 +663,9 @@ efi_status_t efi_set_timer(struct efi_event *event, enum efi_timer_delay type,
 /* Call this to signal an event */
 void efi_signal_event(struct efi_event *event);
 
+/* return true if the device is removable */
+bool efi_disk_is_removable(efi_handle_t handle);
+
 /* open file system: */
 struct efi_simple_file_system_protocol *efi_simple_file_system(
 		struct blk_desc *desc, int part, struct efi_device_path *dp);

lib/efi_loader/efi_disk.c

@@ -73,6 +73,33 @@ static efi_status_t EFIAPI efi_disk_reset(struct efi_block_io *this,
 	return EFI_EXIT(EFI_SUCCESS);
 }
 
+/**
+ * efi_disk_is_removable() - check if the device is removable media
+ * @handle:		efi object handle;
+ *
+ * Examine the device and determine if the device is a local block device
+ * and removable media.
+ *
+ * Return:		true if removable, false otherwise
+ */
+bool efi_disk_is_removable(efi_handle_t handle)
+{
+	struct efi_handler *handler;
+	struct efi_block_io *io;
+	efi_status_t ret;
+
+	ret = efi_search_protocol(handle, &efi_block_io_guid, &handler);
+	if (ret != EFI_SUCCESS)
+		return false;
+
+	io = handler->protocol_interface;
+
+	if (!io || !io->media)
+		return false;
+
+	return (bool)io->media->removable_media;
+}
+
 enum efi_disk_direction {
 	EFI_DISK_READ,
 	EFI_DISK_WRITE,