Random number generation
Hardware random number generation
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intdm_rng_read(structudevice *dev, void*buffer, size_tsize)
read a random number seed from the rng device
Parameters
struct udevice *devrandom number generator device
void *bufferinput buffer to put the read random seed into
size_t sizenumber of random bytes to read
Description
The function blocks until the requested number of bytes is read.
Return
0 if OK, -ve on error
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structdm_rng_ops
operations for the hwrng uclass
Definition
struct dm_rng_ops {
int (*read)(struct udevice *dev, void *data, size_t max);
};
Members
readread a random bytes
The function blocks until the requested number of bytes is read.
read.dev: random number generator device read.data: input buffer to read the random seed into read.max: number of random bytes to read read.Return: 0 if OK, -ve on error
Description
This structures contains the function implemented by a hardware random number generation device.
Pseudo random number generation
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voidsrand(unsignedintseed)
Set the random-number seed value
Parameters
unsigned int seedNew seed
Description
This can be used to restart the pseudo-random-number sequence from a known point. This affects future calls to rand() to start from that point
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unsignedintrand(void)
Get a 32-bit pseudo-random number
Parameters
voidno arguments
Return
next random number in the sequence
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unsignedintrand_r(unsignedint*seedp)
Get a 32-bit pseudo-random number
Parameters
unsigned int *seedpseed value to use, updated on exit
Description
This version of the function allows multiple sequences to be used at the same time, since it requires the caller to store the seed value.
Return
next random number in the sequence