tty: tty_buffer: warn if losing flags in __tty_insert_flip_string_flags()

And add a WARN_ON_ONCE(need_flags) to make sure we are not losing flags
in __tty_insert_flip_string_flags().

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230816105530.3335-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 94a88dc05a54a46ec58a518ebec2a74a3b901635..c101b4ab737e54bf305fed9564d7b683b645b478 100644 (file)
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -325,6 +325,9 @@ int __tty_insert_flip_string_flags(struct tty_port *port, const u8 *chars,
                        flags += space;
                } else if (tb->flags) {
                        memset(flag_buf_ptr(tb, tb->used), flags[0], space);
+               } else {
+                       /* tb->flags should be available once requested */
+                       WARN_ON_ONCE(need_flags);
                }
 
                tb->used += space;