On Thu, 2022-04-28 at 20:11 +0300, Ilpo Järvinen wrote:
> uart_throttle() assumes that a driver provides a throttle function in
> uart_ops. But not all drivers do and there seems to nothing in
> serial_core that would set it either. Thus, check it before calling.
If the driver does not provide throttle function, it should not
set UPSTAT_AUTORTS nor UPSTAT_AUTOXOFF in port->status.
> diff --git a/drivers/tty/serial/serial_core.c
> b/drivers/tty/serial/serial_core.c
> index 6a8963caf954..18c9d46e0b85 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -697,7 +697,8 @@ static void uart_throttle(struct tty_struct *tty)
> mask |= UPSTAT_AUTORTS;
>
> if (port->status & mask) {
This if condition is always false if driver did not set UPSTAT_AUTORTS
nor UPSTAT_AUTOXOFF in port->status.
> - port->ops->throttle(port);
> + if (port->ops->throttle)
> + port->ops->throttle(port);
> mask &= ~port->status;
> }
>
I think this patch is incorrect. The assumption is not ".throttle is
always set" but rather ".throttle is set when UPSTAT_AUTORTS or
UPSTAT_AUTOXOFF is set".
Best Regards,
Tomasz Mon
