random: create add_device_randomness() interface

 * The current exported interfaces for gathering environmental noise

 * from the devices are:

 *

 *	void add_device_randomness(const void *buf, unsigned int size);

 * 	void add_input_randomness(unsigned int type, unsigned int code,

 *                                unsigned int value);

 *	void add_interrupt_randomness(int irq, int irq_flags);

 * 	void add_disk_randomness(struct gendisk *disk);

 *

 * add_device_randomness() is for adding data to the random pool that

 * is likely to differ between two devices (or possibly even per boot).

 * This would be things like MAC addresses or serial numbers, or the

 * read-out of the RTC. This does *not* add any actual entropy to the

 * pool, but it initializes the pool to different values for devices

 * that might otherwise be identical and have very little entropy

 * available to them (particularly common in the embedded world).

 *

 * add_input_randomness() uses the input layer interrupt timing, as well as

 * the event type information from the hardware.

 *

}

#endif

/*

 * Add device- or boot-specific data to the input and nonblocking

 * pools to help initialize them to unique values.

 *

 * None of this adds any entropy, it is meant to avoid the

 * problem of the nonblocking pool having similar initial state

 * across largely identical devices.

 */

void add_device_randomness(const void *buf, unsigned int size)

{

	unsigned long time = get_cycles() ^ jiffies;

	mix_pool_bytes(&input_pool, buf, size, NULL);

	mix_pool_bytes(&input_pool, &time, sizeof(time), NULL);

	mix_pool_bytes(&nonblocking_pool, buf, size, NULL);

	mix_pool_bytes(&nonblocking_pool, &time, sizeof(time), NULL);

}

EXPORT_SYMBOL(add_device_randomness);

static struct timer_rand_state input_timer_state;

/*

extern void rand_initialize_irq(int irq);

extern void add_device_randomness(const void *, unsigned int);

extern void add_input_randomness(unsigned int type, unsigned int code,

				 unsigned int value);

extern void add_interrupt_randomness(int irq, int irq_flags);