[PATCH 6.12.y 1/3] tty: introduce tty_port_tty guard()

[Sasha Levin <sashal@kernel.org>]

From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>

[ Upstream commit e8398b8aed50382c21fcec77e80a5314e7c45c25 ]

Having this, guards like these work:
  scoped_guard(tty_port_tty, port)
    tty_wakeup(scoped_tty());

See e.g. "tty_port: use scoped_guard()" later in this series.

The definitions depend on CONFIG_TTY. It's due to tty_kref_put().
On !CONFIG_TTY, it is an inline and its declaration would conflict. The
guards are not needed in that case, of course.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250814072456.182853-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 56964f6a3123 ("tty: tty_port: restore TTY_IO_ERROR on activation failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/tty_port.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/tty_port.h b/include/linux/tty_port.h
index 41b1c72745ca5..5e2cd738aceaf 100644
--- a/include/linux/tty_port.h
+++ b/include/linux/tty_port.h
@@ -273,4 +273,18 @@ static inline void tty_port_tty_vhangup(struct tty_port *port)
 	__tty_port_tty_hangup(port, false, false);
 }
 
+#ifdef CONFIG_TTY
+void tty_kref_put(struct tty_struct *tty);
+__DEFINE_CLASS_IS_CONDITIONAL(tty_port_tty, true);
+__DEFINE_UNLOCK_GUARD(tty_port_tty, struct tty_struct, tty_kref_put(_T->lock));
+static inline class_tty_port_tty_t class_tty_port_tty_constructor(struct tty_port *tport)
+{
+	class_tty_port_tty_t _t = {
+		.lock = tty_port_tty_get(tport),
+	};
+	return _t;
+}
+#define scoped_tty()	((struct tty_struct *)(__guard_ptr(tty_port_tty)(&scope)))
+#endif
+
 #endif
-- 
2.53.0