On Wed, Jan 31, 2024 at 11:37:20PM +0100, Linus Walleij wrote:
> The ath9k has an odd use of system-wide GPIOs: if the chip
> does not have internal GPIO capability, it will try to obtain a
> GPIO line from the system GPIO controller:
>
> if (BIT(gpio) & ah->caps.gpio_mask)
> ath9k_hw_gpio_cfg_wmac(...);
> else if (AR_SREV_SOC(ah))
> ath9k_hw_gpio_cfg_soc(ah, gpio, out, label);
>
> Where ath9k_hw_gpio_cfg_soc() will attempt to issue
> gpio_request_one() passing the local GPIO number of the controller
> (0..31) to gpio_request_one().
>
> This is somewhat peculiar and possibly even dangerous: there is
> nowadays no guarantee of the numbering of these system-wide
> GPIOs, and assuming that GPIO 0..31 as used by ath9k would
> correspond to GPIOs 0..31 on the system as a whole seems a bit
> wild.
>
> My best guess is that everyone actually using this driver has
> support for the local (custom) GPIO API and the bit in
> h->caps.gpio_mask is always set for any GPIO the driver may
> try to obtain, so this facility to use system-wide GPIOs is
> actually unused and could be deleted.
>
> Anyway: I cannot know if this is really the case, so implement
> a fallback handling using GPIO descriptors obtained from the
> ah->dev device indexed 0..31. These can for example be passed
> in the device tree, ACPI or through board files. I doubt that
> anyone will use them, but this makes it possible to obtain a
> system-wide GPIO for any of the 0..31 GPIOs potentially
> requested by the driver.
...
> + /* Obtains a system specific GPIO descriptor from another GPIO controller */
> + gpiod = devm_gpiod_get_index(ah->dev, NULL, gpio, flags);
> +
Unnecessary blank line, please don't add it.
> + if (IS_ERR(gpiod)) {
> + err = PTR_ERR(gpiod);
> ath_err(ath9k_hw_common(ah), "request GPIO%d failed:%d\n",
> gpio, err);
> return;
> }
--
With Best Regards,
Andy Shevchenko
