linux-kernel - Re: [PATCH] tty: serial: cpm_uart: Fix behaviour for non existing GPIOs

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Date:   Mon, 8 Jun 2020 08:41:05 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: serial: cpm_uart: Fix behaviour for non existing
 GPIOs

On Sat, Jun 06, 2020 at 07:30:21AM +0000, Christophe Leroy wrote:
> devm_gpiod_get_index() doesn't return NULL but -ENOENT when the
> requested GPIO doesn't exist,  leading to the following messages:
> 
> [    2.742468] gpiod_direction_input: invalid GPIO (errorpointer)
> [    2.748147] can't set direction for gpio #2: -2
> [    2.753081] gpiod_direction_input: invalid GPIO (errorpointer)
> [    2.758724] can't set direction for gpio #3: -2
> [    2.763666] gpiod_direction_output: invalid GPIO (errorpointer)
> [    2.769394] can't set direction for gpio #4: -2
> [    2.774341] gpiod_direction_input: invalid GPIO (errorpointer)
> [    2.779981] can't set direction for gpio #5: -2
> [    2.784545] ff000a20.serial: ttyCPM1 at MMIO 0xfff00a20 (irq = 39, base_baud = 8250000) is a CPM UART
> 
> Use IS_ERR_OR_NULL() to properly check gpiod validity.

Why check for NULL at all?

> Fixes: 97cbaf2c829b ("tty: serial: cpm_uart: Convert to use GPIO descriptors")
> Cc: stable@...r.kernel.org
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  drivers/tty/serial/cpm_uart/cpm_uart_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
> index a04f74d2e854..3cbe24802296 100644
> --- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
> +++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
> @@ -1217,7 +1217,7 @@ static int cpm_uart_init_port(struct device_node *np,
>  
>  		gpiod = devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
>  
> -		if (gpiod) {
> +		if (!IS_ERR_OR_NULL(gpiod)) {
>  			if (i == GPIO_RTS || i == GPIO_DTR)
>  				ret = gpiod_direction_output(gpiod, 0);
>  			else

Johan