linux-kernel - Re: [PATCH 1/7] random: cleanup poolinfo abstraction

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Message-ID: <YeQcl1q1L4+oKHPc@owl.dominikbrodowski.net>
Date:   Sun, 16 Jan 2022 14:24:39 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH 1/7] random: cleanup poolinfo abstraction

Am Thu, Jan 13, 2022 at 04:44:07PM +0100 schrieb Jason A. Donenfeld:
> Now that we're only using one polynomial, we can cleanup its
> representation into constants, instead of passing around pointers
> dynamically to select different polynomials. This improves the codegen
> and makes the code a bit more straightforward.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

> -} poolinfo_table[] = {
> -	/* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
> +enum poolinfo {
> +	POOL_WORDS = 128,
> +	POOL_WORDMASK = POOL_WORDS - 1,
> +	POOL_BYTES = POOL_WORDS * sizeof(u32),
> +	POOL_BITS = POOL_BYTES * 8,
> +	POOL_BITSHIFT = ilog2(POOL_WORDS) + 5,
> +	POOL_FRACBITS = POOL_WORDS << (ENTROPY_SHIFT + 5),
> +
>  	/* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
> -	{ S(128),	104,	76,	51,	25,	1 },
> +	POOL_TAP1 = 104,
> +	POOL_TAP2 = 76,

The only information lost seems to be that POOL_TAP1 used to be 103. But
that comment is still available in git history, so feel free to add:

	Reviewed-by: Dominik Brodowski <linux@...inikbrodowski.net>

Thanks,
	Dominik