ntdll: Finish serial reads of size 0 immediately.

dlls/kernel32/tests/comm.c

@@ -2151,13 +2151,9 @@ static void test_read_write(void)
                     iob.Information = -1;
                     offset.QuadPart = (LONGLONG)i;
                     status = pNtReadFile(hcom, 0, NULL, NULL, &iob, buf, 0, &offset, NULL);
-                    /* FIXME: Remove once Wine is fixed */
-                    if (status == STATUS_PENDING) WaitForSingleObject(hcom, TIMEOUT);
                     if (i >= 0)
                     {
-todo_wine
                         ok(status == STATUS_SUCCESS, "%d: expected STATUS_SUCCESS, got %#x\n", i, status);
-todo_wine
                         ok(U(iob).Status == STATUS_SUCCESS, "%d: expected STATUS_SUCCESS, got %#x\n", i, U(iob).Status);
                         ok(iob.Information == 0, "%d: expected 0, got %lu\n", i, iob.Information);
                     }

dlls/ntdll/file.c

@@ -883,6 +883,11 @@ NTSTATUS WINAPI NtReadFile(HANDLE hFile, HANDLE hEvent,
                     status = length ? STATUS_END_OF_FILE : STATUS_SUCCESS;
                     goto done;
                 case FD_TYPE_SERIAL:
+                    if (!length)
+                    {
+                        status = STATUS_SUCCESS;
+                        goto done;
+                    }
                     break;
                 default:
                     status = STATUS_PIPE_BROKEN;