It is useful in embedded. For example, you may see something like [1]: let _clocks = rcc .cfgr .hse(HSEClock::new(25_000_000.Hz(), HSEClock

It is useful in embedded. For example, you may see something like [1]: let _clocks = rcc .cfgr .hse(HSEClock::new(25_000_000.Hz(), HSEClockMode::Bypass)) .sysclk(216_000_000.Hz()) .hclk(216_000_000.Hz()) .freeze(); where the freeze function does a lot of calculation to set up the peripheral [2]. [1]: https://github.com/stm32-rs/stm32f7xx-hal/blob/0a0d06d5f63c3a1471362370fdfb8c367207d308/examples/can-echo.rs#L28-L33 https://github.com/stm32-rs/stm32f7xx-hal/blob/0a0d06d5f63c3... [2]: https://github.com/stm32-rs/stm32f7xx-hal/blob/0a0d06d5f63c3a1471362370fdfb8c367207d308/src/rcc.rs#L746 https://github.com/stm32-rs/stm32f7xx-hal/blob/0a0d06d5f63c3...