GPIO Linux offset mapping

[Or_Asnin]

How can I get the gpio offset in linux ?

Thanks

[Loic]

The gpio number attributed to a gpio by Linux is not something really stable and can change across kernel versions (and sometime even across reboots). When you want to control a pin as a gpio you need to identify which gpio-controller (gpiochip) is in charge of that pin and what is the index/offset inside this gpio-controller. Most of the systems have only one gpio-controller part of the SoC, but some boards like the dragonboards have additional hardware(s) acting as gpio controller (e.g. the pmic).

The content of /sys/kernel/debug/gpio should give you the connection between of the gpio numbers and their gpiochip/offset.

Also from user-space I strongly suggest to use gpiolib get info or control a gpio:

Db845 : gpio 1,2,3 and 4

Well no sure which GPIO you refer here since SoC GPIO_1 is routed to CAN bus… If you look in /sys/class/gpio you’ll find three gpio controller, one of them is the primary pin controller (gpiochip361). That means gpios are indexed starting at 361 for this controller. So to the GPIO_1 you see on schematics is gpio 361 under linux. For example to control GPIO_10 which is routed to Low Speed Connector 1 pin 29, you can do the following: $ echo 371 > /sys/class/gpio/export $ echo out > sys/class/gpi…

To avoid looking at the schematics to find the right SoC gpio connected to the expension connectors, 96boards usually have their gpio ‘labelled’ so that you can easily find which gpio you need to use. For example on a dragonboard-410c:

$ gpiodetect
gpiochip0 [1000000.pinctrl] (122 lines)
gpiochip1 [200f000.spmi:pm8916@0:gpios@c00] (4 lines)
gpiochip2 [200f000.spmi:pm8916@0:mpps@a000] (4 lines)

$ gpioinfo
gpiochip0 - 122 lines:
line   0: "[UART0_TX]"       unused   input  active-high 
line   1: "[UART0_RX]"       unused   input  active-high 
line   2: "[UART0_CTS_N]" unused input active-high 
line   3: "[UART0_RTS_N]" unused input active-high 
line   4: "[UART1_TX]"       unused  output  active-high 
line   5: "[UART1_RX]"       unused  output  active-high 
line   6: "[I2C0_SDA]"       unused   input  active-high 
line   7: "[I2C0_SCL]"       unused   input  active-high 
line   8: "[SPI1_DOUT]" unused input active-high 
line   9: "[SPI1_DIN]"       unused   input  active-high 
line  10:  "[SPI1_CS]"       unused   input  active-high 
line  11: "[SPI1_SCLK]" unused input active-high 
line  12:     "GPIO-B"       unused   input  active-high 
line  13:     "GPIO-C"       unused   input  active-high 
    ...

So here you can set GPIO-B (Low speed connectot[1]) to high with

gpioset gpiochip0 12=1

or

gpioset 1000000.pinctrl 12=1

[1] 96Boards GPIO Pinout

[Or_Asnin]

Hi thanks for the information.

I work with android shell, any other way ?

[Or_Asnin]

Thanks

[Loic]

@Or_Asnin

I work with android shell, any other way ?

Either you build gpiolib for android, or you use the ‘legacy’ method via /sys/class/gpio: GPIO - eLinux.org

You can use cat /sys/kernel/debug/gpio to get the mapping.

[Gustavo_Gonzales_Lop]

Thanks! …
This is the solution…