The code was taken from https://github.com/digitalloggers/i2c-gpio-custom with some modifications:
- removed support for older kernels
- make it work with newer kernel >= 5.15.x
- renamed it to "i2c-gpiod-custom"
- Add it into your OpenWrt build folder. I always create a new folder in packages (e.g. packages/mypackages)
- Clone this repository to packages/mypackages
make menuconfig-> select i2c-gpiod-custom- build OpenWrt.
insmod i2c-gpiod-custom bus0=0,18,19
Now you should have a new i2c device file in /dev e.g:
/dev/i2c-0
If you connect some i2c device you can now use i2c-tools e.g.:
root@OpenWrt:/# i2cdetect -y 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1e --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- 53 -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- 77
Checking with gpiod tools you can see that the i2c pins are now reserved:
Note: With openwrt-23.05 this only works if GPIO_CDEV_V1 is enabled in the kernel.
root@OpenWrt:/# gpioinfo
gpiochip0 - 32 lines:
line 0: unnamed "green:wlan" output active-low [used]
line 1: unnamed unused output active-high
line 2: unnamed unused output active-high
line 3: unnamed unused output active-high
line 4: unnamed unused output active-high
line 5: unnamed unused output active-high
line 6: unnamed unused output active-high
line 7: unnamed unused output active-high
line 8: unnamed unused input active-high
line 9: unnamed unused input active-high
line 10: unnamed unused output active-high
line 11: unnamed "wps" input active-low [used]
line 12: unnamed unused input active-high
line 13: unnamed "orange:eth0" output active-high [used]
line 14: unnamed "orange:eth1" output active-high [used]
line 15: unnamed unused input active-high
line 16: unnamed unused input active-high
line 17: unnamed unused input active-high
line 18: unnamed "sda" output active-high [used open-drain]
line 19: unnamed "scl" output active-high [used open-drain]
line 20: unnamed unused input active-high
line 21: unnamed unused input active-high
line 22: unnamed unused input active-high
line 23: unnamed unused input active-high
line 24: unnamed unused input active-high
line 25: unnamed unused input active-high
line 26: unnamed unused input active-high
line 27: unnamed unused input active-high
line 28: unnamed unused input active-high
line 29: unnamed unused input active-high
line 30: unnamed unused input active-high
line 31: unnamed unused input active-high