Re: [PATCH] serial: 8250_omap: Fix gpio check for auto RTS and CTS

[Yegor Yefremov]

Hi Adam,

On Sun, Oct 6, 2019 at 4:33 AM Adam Ford <aford173@xxxxxxxxx> wrote:
>
> There are two checks to see if the manual gpio is configured, but
> these the check is seeing if the structure is NULL instead it
> should check to see if there are CTS and/or RTS pins defined.
>
> This patch uses checks for those individual pins instead of
> checking for the structure itself.
>
> Signed-off-by: Adam Ford <aford173@xxxxxxxxx>
>
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index c68e2b3a1634..836e736ae188 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -141,7 +141,7 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
>
>         serial8250_do_set_mctrl(port, mctrl);
>
> -       if (!up->gpios) {
> +       if (!mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS)) {
>                 /*
>                  * Turn off autoRTS if RTS is lowered and restore autoRTS
>                  * setting if RTS is raised
> @@ -456,7 +456,8 @@ static void omap_8250_set_termios(struct uart_port *port,
>         up->port.status &= ~(UPSTAT_AUTOCTS | UPSTAT_AUTORTS | UPSTAT_AUTOXOFF);
>
>         if (termios->c_cflag & CRTSCTS && up->port.flags & UPF_HARD_FLOW &&
> -           !up->gpios) {
> +           !mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS) &&
> +           !mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_CTS)) {
>                 /* Enable AUTOCTS (autoRTS is enabled when RTS is raised) */
>                 up->port.status |= UPSTAT_AUTOCTS | UPSTAT_AUTORTS;
>                 priv->efr |= UART_EFR_CTS;

Looks good to me but !up->gpios must remain as otherwise, we will get
NULL pointer dereference. What do you think?

Also adding some more people who can be interested in testing this approach.

Cheers,
Yegor