@@ -382,7 +382,7 @@ mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {
 
 STATIC mp_obj_t stream_seek(mp_uint_t n_args, const mp_obj_t *args) {
     struct _mp_obj_base_t *o = (struct _mp_obj_base_t *)args[0];
-    if (o->type->stream_p == NULL || o->type->stream_p->read == NULL) {
+    if (o->type->stream_p == NULL || o->type->stream_p->ioctl == NULL) {
         // CPython: io.UnsupportedOperation, OSError subclass
         nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));
     }
 
@@ -260,6 +260,7 @@ const mp_obj_type_t mp_type_fileio = {
 STATIC const mp_stream_p_t textio_stream_p = {
     .read = file_obj_read,
     .write = file_obj_write,
+    .ioctl = file_obj_ioctl,
     .is_text = true,
 };
 
 
@@ -10,3 +10,11 @@
 
 print(f.seek(0, 0))
 print(f.read(5))
+
+f.close()
+
+# test text mode
+f = open("io/data/file1", "rt")
+print(f.seek(6))
+print(f.read(5))
+f.close()
@@ -240,6 +240,7 @@ const mp_obj_type_t mp_type_fileio = {
 STATIC const mp_stream_p_t textio_stream_p = {
     .read = fdfile_read,
     .write = fdfile_write,
+    .ioctl = fdfile_ioctl,
     .is_text = true,
 };
Original file line number	Diff line number	Diff line change
`@@ -382,7 +382,7 @@ mp_obj_t mp_stream_unbuffered_iter(mp_obj_t self) {`
`382`	`382`
`383`	`383`	`STATIC mp_obj_t stream_seek(mp_uint_t n_args, const mp_obj_t *args) {`
`384`	`384`	`struct _mp_obj_base_t o = (struct _mp_obj_base_t )args[0];`
`385`		`- if (o->type->stream_p == NULL \|\| o->type->stream_p->read == NULL) {`
	`385`	`+ if (o->type->stream_p == NULL \|\| o->type->stream_p->ioctl == NULL) {`
`386`	`386`	`// CPython: io.UnsupportedOperation, OSError subclass`
`387`	`387`	`nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "Operation not supported"));`
`388`	`388`	`}`