linux-kernel - Re: [PATCH] serial: core: remove silly test for uart

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Date:   Fri, 6 Jan 2017 19:22:43 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Thadeu Lima de Souza Cascardo <cascardo@...cardo.eti.br>,
        Peter Hurley <peter@...leysoftware.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH] serial: core: remove silly test for uart_state

On Fri, Jan 6, 2017 at 4:45 AM, Thadeu Lima de Souza Cascardo
<cascardo@...cardo.eti.br> wrote:
> The polling functions were checking for a NULL uart_state, which is
> indexed from uart_driver->state. It should be always allocated and
> non-NULL when the tty_driver is registered, and line should not be
> larger than the tty_driver->num anyways.

I'm not sure this is guaranteed. Let Peter to comment on it.

Peter, what is your opinion?

P.S. If Peter is okay with it, I don't see any problems with code itself either.

>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...cardo.eti.br>
> ---
>  drivers/tty/serial/serial_core.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 9939c3d9912b..6f7247114ef8 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2330,9 +2330,6 @@ static int uart_poll_init(struct tty_driver *driver, int line, char *options)
>         int flow = 'n';
>         int ret = 0;
>
> -       if (!state)
> -               return -1;
> -
>         tport = &state->port;
>         mutex_lock(&tport->mutex);
>
> @@ -2367,12 +2364,10 @@ static int uart_poll_get_char(struct tty_driver *driver, int line)
>         struct uart_port *port;
>         int ret = -1;
>
> -       if (state) {
> -               port = uart_port_ref(state);
> -               if (port) {
> -                       ret = port->ops->poll_get_char(port);
> -                       uart_port_deref(port);
> -               }
> +       port = uart_port_ref(state);
> +       if (port) {
> +               ret = port->ops->poll_get_char(port);
> +               uart_port_deref(port);
>         }
>         return ret;
>  }
> @@ -2383,9 +2378,6 @@ static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
>         struct uart_state *state = drv->state + line;
>         struct uart_port *port;
>
> -       if (!state)
> -               return;
> -
>         port = uart_port_ref(state);
>         if (!port)
>                 return;
> --
> 2.11.0
>



-- 
With Best Regards,
Andy Shevchenko