Messages in this thread | | | Subject | Re: hw_random fixes | From | Matt Mackall <> | Date | Wed, 25 Nov 2009 13:27:32 -0600 |
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[cc:ing to linux-kernel, finally]
On Wed, 2009-11-25 at 10:16 +0000, Ian Molton wrote: > Rusty Russell wrote: > > > Make that: > > > > ssize_t (*get_rng_data)(void *buf, size_t max, bool wait); > > > > Then, if driver supplies that hook, use it exclusively. Otherwise, use old > > ones. We can convert them gradually that way. > > This doesn't quite solve things neatly, because it means one of: > > 1) The core has to wait until there is nothing left before requesting > more data, because it doesnt know the alignment requirements of the driver.
Hmm, this seems to imply you'd be calling get_rng_data multiple times with different offsets into buf to accumulate data. I think that's more complex than is needed. Just use buf as a nicely aligned scratch buffer and empty it completely into the final output buffer before the next driver request. If you end up with 1 byte of data hanging around until the next read, that's not a problem - the next read might be 5 bytes.
You'll probably want to use cacheline alignment on buf to make Via Padlock happy, if anything needs larger alignment (ie page) it should handle it internally.
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