xhci: dbctty: disable ECHO flag by default

When /dev/ttyDBC0 device is created then by default ECHO flag
is set for the terminal device. However if data arrives from
a peer before application using /dev/ttyDBC0 applies its set
of terminal flags then the arriving data will be echoed which
might not be desired behavior.

Fixes: 4521f16 ("xhci: dbctty: split dbc tty driver registration and unregistration functions.")
Cc: stable <[email protected]>
Signed-off-by: Łukasz Bartosik <[email protected]>
Signed-off-by: Mathias Nyman <[email protected]>
Link: https://lore.kernel.org/stable/20250610111802.18742-1-ukaszb%40chromium.org
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Łukasz Bartosik

drivers/usb/host/xhci-dbgtty.c

@@ -617,6 +617,7 @@ int dbc_tty_init(void)
 	dbc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
 	dbc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
 	dbc_tty_driver->init_termios = tty_std_termios;
+	dbc_tty_driver->init_termios.c_lflag &= ~ECHO;
 	dbc_tty_driver->init_termios.c_cflag =
 			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
 	dbc_tty_driver->init_termios.c_ispeed = 9600;