Re: [PATCH v2] serial: max310x: implement gpio_chip::get_direction()

[Bartosz Golaszewski]

On Mon, 15 Jun 2026 08:38:40 +0200, Tapio Reijonen
<tapio.reijonen@xxxxxxxxxxx> said:
> It's strongly recommended for GPIO drivers to always implement the
> .get_direction() callback - even when the direction is tracked in
> software. The GPIO core emits a warning when the callback is missing
> and a user reads the direction of a line, e.g. via
> /sys/kernel/debug/gpio.
>
> The MAX310X keeps the GPIO direction in the GPIOCFG register (a set bit
> selects output), which the existing direction_input/output callbacks
> already program, so the current direction can be read back directly.
>
> Fixes: f65444187a66 ("serial: New serial driver MAX310X")
> Signed-off-by: Tapio Reijonen <tapio.reijonen@xxxxxxxxxxx>
> ---
> Found and HW-tested on an i.MX6 SoloX board with a MAX14830 over SPI:
> without this, "cat /sys/kernel/debug/gpio" triggers the gpiolib.c:429
> WARNING (tainting the kernel W) on each queried MAX14830 line; with it
> applied the lines report their in/out direction and the WARNING is gone.
> ---
> Changes in v2:
> - Address Hugo Villeneuve's review: use BIT(offset % 4) and put the
>   return statement on a single line.
> - Rebase onto v7.1-rc7.
> - Link to v1: https://lore.kernel.org/r/20260602-b4-serial-max310x-gpio-get-direction-v1-1-23bf84e8ee14@xxxxxxxxxxx
> ---

I've already left my tag under this.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>