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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <df4857cb-daae-4428-bd93-5878564624c5@nutanix.com>
Date: Thu, 9 Oct 2025 10:05:58 +0100
From: Mark Cave-Ayland <mark.caveayland@...anix.com>
To: William Breathitt Gray <wbg@...nel.org>, mwalle@...nel.org
Cc: linus.walleij@...aro.org, brgl@...ev.pl, andriy.shevchenko@...ux.intel.com,
        broonie@...nel.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: gpio: gpio-pci-idio-16 regression after LTS upgrade

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@...ian12:~# 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.