esp-idf/components/bootloader_support/include/bootloader_random.h

/*
 * SPDX-FileCopyrightText: 2010-2021 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#pragma once

#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Enable early entropy source for RNG
 *
 * Uses the SAR ADC to feed entropy into the HWRNG. The ADC is put
 * into a test mode that reads the 1.1V internal reference source and
 * feeds the LSB of data into the HWRNG.
 *
 * Can also be used from app code early during operation, if entropy
 * is required before WiFi stack is initialised. Call this function
 * from app code only if WiFi/BT are not yet enabled and I2S and SAR
 * ADC are not in use.
 *
 * Call bootloader_random_disable() when done.
 */
void bootloader_random_enable(void);

/**
 * @brief Disable early entropy source for RNG
 *
 * Disables SAR ADC source and resets the I2S hardware.
 *
 */
void bootloader_random_disable(void);

/**
 * @brief Fill buffer with 'length' random bytes
 *
 * @param buffer Pointer to buffer
 * @param length This many bytes of random data will be copied to buffer
 */
void bootloader_fill_random(void *buffer, size_t length);

#ifdef __cplusplus
}
#endif