linux-kernel - RE: [PATCH] random: cleanup fractional entropy shift constants

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Date:   Fri, 14 Jan 2022 15:39:06 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Jason A. Donenfeld'" <Jason@...c4.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tytso@....edu" <tytso@....edu>
Subject: RE: [PATCH] random: cleanup fractional entropy shift constants

From: Jason A. Donenfeld
> Sent: 14 January 2022 15:33
> 
> The entropy estimator is calculated in terms of 1/8 bits, which means
> there are various constants where things are shifted by 3. Move these
> into our pool info enum with the other relevant constants, and normalize
> the name a bit, prepending a POOL_ like the rest. While we're at it,
> move an English assertion about sizes into a proper BUILD_BUG_ON so
> that the compiler can ensure this invariant.
> 
...
> -#define ENTROPY_SHIFT 3
> -#define ENTROPY_BITS() (input_pool.entropy_count >> ENTROPY_SHIFT)
..
> +	POOL_ENTROPY_SHIFT = 3,
> +#define POOL_ENTROPY_BITS() (input_pool.entropy_count >> POOL_ENTROPY_SHIFT)

The rename ought to be a different patch.

	David

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