Re: [PATCH net-next v2 12/14] gpio: tc956x: add TC956x/QPS615 support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] API Misuse: `fixed_direction_output` completely breaks direction querying and fails to enforce input-only pins.
- [Low] Build failure due to assignment to non-existent member `fixed_direction_mask` in `struct gpio_regmap_config`.
--

commit 5da78e90b4b1867131b8f557ae59d72ce4db9776
Author: Alex Elder <elder@riscstar.com>

gpio: tc956x: add TC956x/QPS615 support

This commit adds a generic regmap-based GPIO driver for the Toshiba TC956x
Ethernet-AVB/TSN bridge. The device acts as an auxiliary device to the PCIe
endpoint function driver.

> diff --git a/drivers/gpio/gpio-tc956x.c b/drivers/gpio/gpio-tc956x.c
> new file mode 100644
> index 0000000000000..0dc6b1028d970
> --- /dev/null
> +++ b/drivers/gpio/gpio-tc956x.c
[ ... ]
> +static int tc956x_gpio_probe(struct auxiliary_device *adev,
> +			     const struct auxiliary_device_id *id)
> +{
[ ... ]
> +	config.reg_stride = GPIO_REG_STRIDE;
> +	config.ngpio_per_reg = GPIO_PER_REG;
> +	config.init_valid_mask = tc956x_gpio_init_valid_mask;
> +	config.fixed_direction_mask = fixed;

[Severity: Low]
Is fixed_direction_mask a valid member of struct gpio_regmap_config?
It does not appear to be defined in include/linux/gpio/regmap.h, which
could lead to a build failure here.

> +	config.fixed_direction_output = zeroes;

[Severity: High]
Does providing an all-zeroes bitmap to fixed_direction_output achieve the
intended input-only constraints?

Looking at gpio_regmap_get_direction() in drivers/gpio/gpio-regmap.c:

	if (gpio->fixed_direction_output) {
		if (test_bit(offset, gpio->fixed_direction_output))
			return GPIO_LINE_DIRECTION_OUT;
		else
			return GPIO_LINE_DIRECTION_IN;
	}

Providing a non-NULL fixed_direction_output causes the API to bypass
hardware direction queries for all pins, unconditionally reporting all
37 pins as inputs.

Furthermore, since reg_dir_in_base is also provided, the API will still
allow users to configure these supposedly input-only pins as outputs
because it does not check fixed_direction_output during set_direction
operations.

> +
> +	gpio_regmap = devm_gpio_regmap_register(dev, &config);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260605010022.968612-1-elder@riscstar.com?part=12