Help regarding IO configuration of multiple lines

Help regarding IO configuration of multiple lines

[joussemetmathis]

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Hello,

I am trying to learn how to use libgpiod on a Pi 5. I created for that
goal a simple circuit with a push button and 2 LEDs, one of which turns
on on a button press.
Since I want to keep my program as modular as possible, I created a
pinconfig function that configures the pins according to the parameters
passed in main.
However, when trying to pass an enum array of gpiod_line_direction to
the function, the code no longer works and the LEDs no longer turn on.
I suspect it is due to the way the array is handled, but since this use
case isn't shown in the examples and that online ressources seems to
only talk about v1 of gpiod, I'm a bit stuck.
Could someone help me? You'll find my code attached in a zip in this
email.

Thanks in advance 

Mathis Joussemet 

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Re: Help regarding IO configuration of multiple lines

[Kent Gibson]

On Fri, Mar 06, 2026 at 12:09:50PM +0100, joussemetmathis@gmail.com wrote:
> Hello,
> 
> I am trying to learn how to use libgpiod on a Pi 5. I created for that
> goal a simple circuit with a push button and 2 LEDs, one of which turns
> on on a button press.
> Since I want to keep my program as modular as possible, I created a
> pinconfig function that configures the pins according to the parameters
> passed in main.
> However, when trying to pass an enum array of gpiod_line_direction to
> the function, the code no longer works and the LEDs no longer turn on.
> I suspect it is due to the way the array is handled, but since this use
> case isn't shown in the examples and that online ressources seems to
> only talk about v1 of gpiod, I'm a bit stuck.
> Could someone help me? You'll find my code attached in a zip in this
> email.
> 

Yeah, the example code doesn't provide a good example of requesting
lines with different settings.
The closest is get_multiple_line_values.c.  Though that applies settings for
each line individually when it could just use a single
gpiod_line_config_add_line_settings() call, as all the lines have the
same settings.  Not sure why.  ¯\_(ツ)_/¯

The relevant section of your code, which seems to follow that example, is:

	gpiod_line_settings_set_direction(line_settings, *direction);
    // ...
	for (int i = 0; i < line_nbr; i++) {
		gpiod_line_config_add_line_settings(line_config, &pin_list[i], 1, line_settings);	
	}


That applies the first entry in your direction array as the direction for all
lines. Definitely not what you want.

See if this works for you:

	for (int i = 0; i < line_nbr; i++) {
	    gpiod_line_settings_set_direction(line_settings, direction[i]);
		gpiod_line_config_add_line_settings(line_config, &pin_list[i], 1, line_settings);	
	}

That applies the direction for each line individually, with other line
settings being the same.

Cheers,
Kent.