diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index e625ef2bcb7f..b7c9270f9e92 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1155,6 +1155,8 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 		bi.bytes_written = 0;
 	} else {
 		/* command was set up in "write" direction */
+		if (!comedi_is_subdevice_running(s))
+			bi.bytes_written = 0;
 		if (bi.bytes_written) {
 			comedi_buf_write_alloc(s, bi.bytes_written);
 			bi.bytes_written =