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

[Linus Walleij]

Hi Christophe!

On Sat, Jun 6, 2020 at 9:30 AM Christophe Leroy
<christophe.leroy@xxxxxxxxxx> wrote:


>                 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

This code, and the way descriptors are used in the driver leads
me to believe that the right solution is to use the optional
call with a hard error check:

gpiod = devm_gpiod_get_index_optional(...);

if (IS_ERR(gpiod))
    return PTR_ERR(gpiod);

if (gpiod) {
... followed by the old code ...

This makes sure that the array member is left NULL if there is no
GPIO on this line, and all other errors, such as -EPROBE_DEFER
which currently absolutely does not work, will lead to us properly
exiting with an error.

Yours,
Linus Walleij