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https://github.com/zephyrproject-rtos/zephyr
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da9b0ddf5b
This should clear up some of the confusion with random number generators and drivers that obtain entropy from the hardware. Also, many hardware number generators have limited bandwidth, so it's natural for their output to be only used for seeding a random number generator. Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
65 lines
1.5 KiB
C
65 lines
1.5 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <string.h>
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#include <entropy.h>
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static inline u32_t entropy_esp32_get_u32(void)
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{
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/* The documentation specifies the random number generator at the
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* following address, which is at odds with the SDK, that specifies
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* it at 0x60035144. The fact that they're 0x200c0000 bytes apart
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* (lower 16 bits are the same) suggests this might be the same
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* register, just mirrored somewhere else in the address space.
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* Confirmation is required.
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*/
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volatile u32_t *rng_data_reg = (u32_t *)0x3ff75144;
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/* Read just once. This is not optimal as the generator has
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* limited throughput due to scarce sources of entropy, specially
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* with the radios turned off. Might want to revisit this.
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*/
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return *rng_data_reg;
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}
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static int entropy_esp32_get_entropy(struct device *device, u8_t *buf, u16_t len)
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{
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while (len) {
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u32_t v = entropy_esp32_get_u32();
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if (len >= sizeof(v)) {
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memcpy(buf, &v, sizeof(v));
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buf += sizeof(v);
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len -= sizeof(v);
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} else {
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memcpy(buf, &v, len);
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break;
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}
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}
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return 0;
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}
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static int entropy_esp32_init(struct device *device)
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{
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return 0;
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}
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static struct entropy_driver_api entropy_esp32_api_funcs = {
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.get_entropy = entropy_esp32_get_entropy
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};
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DEVICE_AND_API_INIT(entropy_esp32, CONFIG_ENTROPY_NAME,
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entropy_esp32_init, NULL, NULL,
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PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
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&entropy_esp32_api_funcs);
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u32_t sys_rand32_get(void)
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{
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return random_esp32_get_u32();
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}
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