Struct EntropySource 

pub struct EntropySource { /* private fields */ }

This is a wrapper that sets up the boot entropy source.

On chips with a TRNG this holds the SAR ADC entropy source that init_entropy() enables. The RNG register only has randomness while a source is active, and the ADC source is what occurs on boot.

Dropping this guard switches off the source. This handover is required because the ADC source needs to be switched off “before RF subsystem features, ADC, or I2S (ESP32 only) are initialized” and that it’s “not safe to use if any other subsystem is accessing the RF subsystem or the ADC at the same time”.

On the ESP32-C5/C61, there is no TRNG driver yet, so the guard is empty.

See: https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/random.html