Cargo Features

[dependencies]
stm32c0xx-hal = { version = "0.0.0", default-features = false, features = ["stm32c0x1", "i2c-blocking", "i2c-nonblocking"] }
default = i2c-blocking

The i2c-blocking feature is set by default whenever stm32c0xx-hal is added without default-features = false somewhere in the dependency tree.

device-selected stm32c0x0 stm32c0x1
i2c-blocking default
i2c-nonblocking

stm32c0xx-hal has 4 features without comments.