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SubjectRe: [PATCH] hwrng: document the quality field
On Tue, Sep 25, 2018 at 12:35:18PM -0400, Michael S. Tsirkin wrote:
> quality field is currently documented as being 'per mill'. In fact the
> math involved is:
>
> add_hwgenerator_randomness((void *)rng_fillbuf, rc,
> rc * current_quality * 8 >> 10);
>
> thus the actual definition is "bits of entropy per 1024 bits of input".
>
> The current documentation seems to have confused multiple people
> in the past, let's fix the documentation to match code.
>
> An alternative is to change core to match driver expectations, replacing
> rc * current_quality * 8 >> 10
> with
> rc * current_quality / 1000
> but that has performance costs, so probably isn't a good option.
>
> Fixes: 0f734e6e768 ("hwrng: add per-device entropy derating")
> Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
>
> drivers/char/hw_random/core.c | 4 ++--
> include/linux/hw_random.h | 3 ++-
> 2 files changed, 4 insertions(+), 3 deletions(-)

Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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