I am currently attempting to figure out which number I need to be feeding gpiolib in order to toggle a pin from the user-space so if someone can help explain it would be helpful. For instance, here is a comment from a co-worker about a different system and a different GPIO:

"...circuit is a subset of this), J2-63 GPIO4_11 (SPKR_MUTE) (gpio107 in the kernel) drives a buffer that drives..."

The code in the user space calls this pin 107 in order to toggle it. So my question is, where does this number 107 come from? I realize this question is kind of vague and I apologize for that. I would just ask my coworker but he is out of town. I did a grep search in the kernel for gpio107 and nothing comes up. I just don't understand how a pin goes from being called J2-63 GPIO4_11 too 107.

 

https://www.kernel.org/doc/html/v4.17/driver-api/gpio/index.html
https://www.kosagi.com/w/index.php?title=Definitive_GPIO_guide#Linux_Userspace_Naming_Convention

 

I just don't understand how a pin goes from being called J2-63 GPIO4_11 too 107.

With the ARM based system I'm using, there's a formula to convert from what the MCU calls the I/O's and the number you use from the Shell or sysfs.

 

Hey awesome thanks to both of you, great help!

 

Hey awesome thanks to both of you, great help!

The GPIO sub-system is a convoluted mess because there are several 'official' Legacy methods to handle them. I normally use the direct GPIO controller memory read/write instructions in kernel drivers that don't need direct OS user consumer level manipulations as it's much faster to bit toggle but that method is device specific.

 

Hey awesome thanks to both of you, great help!

For my ARM based board, the ports are named as follows:





To calculate the port number for port PD2, the formula (for my board) is:
('D' - 'A') * 32 + 2 = 98