I2C is used at run time in 10 crates (of which 8 optionally). It is a direct run-time dependency in 4 crates.

Depender (with downloads and own rev deps) I2C version
650 1 ddc-i2c ^0.1
2.0K 4 i2c-linux optional ^0.1.0
i2c-i2cdev ^0.1.0
460 2 nvapi optional ^0.1.0