Re: gpio: gpio-pci-idio-16 regression after LTS upgrade

[Mark Cave-Ayland <mark.caveayland@nutanix.com>]

On 07/10/2025 09:16, William Breathitt Gray wrote:

> On Mon, Oct 06, 2025 at 09:37:14AM +0100, Mark Cave-Ayland wrote:
>> root@debian12:~# gpioget 0 0
>> gpioget: error reading GPIO values: Input/output error
>>
>> which also output:
>>
>> [  329.529321] gpio-512 (gpioget): gpiod_direction_input: missing
>> direction_input() operation and line is output
>>
>> My guess is that this is because
>> drivers/gpio/gpio-regmap.c::gpio_regmap_get_direction() isn't able to
>> can't handle the situation where lines 0-15 are outputs and lines 16-31
>> are inputs, compared with the old idio_16_gpio_get_direction() function
>> it replaced.
>>
>> What would be the best way forward? Possibly add the .get_direction
>> callback to the gpio_regmap_config? Or is there another way to have
>> mixed inputs and outputs with the gpio_regmap API?
> 
> So the intention I had with gpio-idio-16 was to provide reg_dat_base and
> reg_set_base to define the input and output bases, and then
> reg_mask_xlate would do the translation between input and outputs. I
> think this design is allowed by gpio-regmap, is it not Michael?
> 
> In theory, gpio_regmap_get_direction should call gpio->reg_mask_xlate()
> which is mapped to idio_16_reg_mask_xlate(), and thus set reg and mask
> which then is evaluated at the end of gpio_regmap_get_direction() to
> determine which direction to return.
> 
> Is it possible idio_16_reg_mask_xlate() is returning the wrong values
> for reg and mask?
> 
> William Breathitt Gray

The only logic around .reg_dat_base and .reg_set_base in 
gpio_regmap_get_direction() is this:

	if (gpio->reg_dat_base && !gpio->reg_set_base)
		return GPIO_LINE_DIRECTION_IN;
	if (gpio->reg_set_base && !gpio->reg_dat_base)
		return GPIO_LINE_DIRECTION_OUT;

Otherwise it attempts to use .reg_dir_out_base and .reg_dir_in_base 
which are not set for gpio-idio-16 because the GPIO directions are fixed 
and not controlled via a data-direction register. And as these are not 
set, gpio_regmap_get_direction() returns -ENOTSUPP.

Were you thinking that gpio_regmap_get_direction() should have some 
additional direction logic if both .reg_dat_base and .reg_set_base are 
set, based upon their comparative values?


ATB,

Mark.