chore: import upstream snapshot with attribution

components/bootloader_support/include/bootloader_random.h

@@ -0,0 +1,60 @@
+/*
+ * 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 an entropy source for RNG if RF subsystem is disabled
+ *
+ * @warning If use ADC as entropy source, this function is not safe
+ * if any other subsystem is accessing the RF subsystem or the ADC at the same time!
+ *
+ * The exact internal entropy source mechanism depends on the chip in use but
+ * all SoCs use the SAR ADC to continuously mix random bits (an internal
+ * noise reading) into the HWRNG. Consult the SoC Technical Reference
+ * Manual for more information.
+ *
+ * Can also be called from app code, if true random numbers are required without initialized RF subsystem.
+ * This might be the case in early startup code of the application when the RF subsystem has not
+ * started yet or if the RF subsystem should not be enabled for power saving.
+ *
+ * Consult ESP-IDF Programming Guide "Random Number Generation" section for
+ * details.
+ */
+void bootloader_random_enable(void);
+
+/**
+ * @brief Disable entropy source for RNG
+ *
+ * Disables internal entropy source. Must be called after
+ * bootloader_random_enable() and before RF subsystem features, ADC, or
+ * I2S (ESP32 only) are initialized.
+ *
+ * Consult the ESP-IDF Programming Guide "Random Number Generation"
+ * section for details.
+ */
+void bootloader_random_disable(void);
+
+/**
+ * @brief Fill buffer with 'length' random bytes
+ *
+ * @note If this function is being called from app code only, and never
+ * from the bootloader, then it's better to call esp_fill_random().
+ *
+ * @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