> But isn't that what's happening all the time anyway, with the "environmental noise from
device drivers and other sources"
No. The various sources of entropy add entropy to the random pool and increase the entropy
estimate by some small value.
You may want to see for yourself in the kernel sources -- they end up calling
add_timer_randomness (drivers/char/random.c line 571) which calls add_entropy_words and then
credit_entropy_store. This increases the value of entropy_count, and may cause processes
blocking on /dev/random to wake up.