Thursday, 19 July 2012

IRQF_SAMPLE_RANDOM on its way out

According to Linux Weekly News article 507115 , the flag IRQF_SAMPLE_RANDOM, which
drivers use to tell the kernel whether to use interrupts from their
device(s) as a source of entropy for the entropy pool that backs the
kernel's RNG or not, is liable to become redundant from 3.6 onwards.
"After this change, adding randomness from interrupts ... is done by
default for all interrupts". This means that at that point I can remove
the flag in my out-of-line pciaer driver
( along with the handling
of a module parameter (no_sample_random) which I provided to allow
paranoiacs to turn the use of IRQF_SAMPLE_RANDOM off. This might have
been important if very regular address-event senders and/or receivers
were in use (e.g. during test) but high quality random-number generation
were still important.

I've queued this change up in my TODO file.