linux-kernel - Re: [PATCH v2 1/3] powerpc/microwatt: wire up rng during setup

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Message-ID: <6432586f-9eb9-ac71-7934-c48da09a928e@csgroup.eu>
Date:   Sat, 11 Jun 2022 14:40:46 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] powerpc/microwatt: wire up rng during setup_arch



Le 11/06/2022 à 12:04, Jason A. Donenfeld a écrit :
> The platform's RNG must be available before random_init() in order to be
> useful for initial seeding, which in turn means that it needs to be
> called from setup_arch(), rather than from an init call. Fortunately,
> each platform already has a setup_arch function pointer, which means
> it's easy to wire this up for each of the three platforms that have an
> RNG. This commit also removes some noisy log messages that don't add
> much.
> 
> Cc: stable@...r.kernel.org
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Fixes: c25769fddaec ("powerpc/microwatt: Add support for hardware random number generator")
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>   arch/powerpc/platforms/microwatt/rng.c   | 9 ++-------
>   arch/powerpc/platforms/microwatt/setup.c | 8 ++++++++
>   2 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/microwatt/rng.c b/arch/powerpc/platforms/microwatt/rng.c
> index 7bc4d1cbfaf0..d13f656910ad 100644
> --- a/arch/powerpc/platforms/microwatt/rng.c
> +++ b/arch/powerpc/platforms/microwatt/rng.c
> @@ -29,7 +29,7 @@ static int microwatt_get_random_darn(unsigned long *v)
>   	return 1;
>   }
>   
> -static __init int rng_init(void)
> +__init void microwatt_rng_init(void)
>   {
>   	unsigned long val;
>   	int i;
> @@ -37,12 +37,7 @@ static __init int rng_init(void)
>   	for (i = 0; i < 10; i++) {
>   		if (microwatt_get_random_darn(&val)) {
>   			ppc_md.get_random_seed = microwatt_get_random_darn;
> -			return 0;
> +			return;
>   		}
>   	}
> -
> -	pr_warn("Unable to use DARN for get_random_seed()\n");
> -
> -	return -EIO;
>   }
> -machine_subsys_initcall(, rng_init);
> diff --git a/arch/powerpc/platforms/microwatt/setup.c b/arch/powerpc/platforms/microwatt/setup.c
> index 0b02603bdb74..23c996dcc870 100644
> --- a/arch/powerpc/platforms/microwatt/setup.c
> +++ b/arch/powerpc/platforms/microwatt/setup.c
> @@ -32,10 +32,18 @@ static int __init microwatt_populate(void)
>   }
>   machine_arch_initcall(microwatt, microwatt_populate);
>   
> +__init void microwatt_rng_init(void);

This prototype should be declared in a header file, for instance asm/setup.h

checkpatch.pl returns the following warning:

WARNING:AVOID_EXTERNS: externs should be avoided in .c files
#59: FILE: arch/powerpc/platforms/microwatt/setup.c:35:
+__init void microwatt_rng_init(void);

And I think the __init keyword usually goes after the type, so should be 
'void __init'.

> +
> +static void __init microwatt_setup_arch(void)
> +{
> +	microwatt_rng_init();
> +}
> +
>   define_machine(microwatt) {
>   	.name			= "microwatt",
>   	.probe			= microwatt_probe,
>   	.init_IRQ		= microwatt_init_IRQ,
> +	.setup_arch		= microwatt_setup_arch,
>   	.progress		= udbg_progress,
>   	.calibrate_decr		= generic_calibrate_decr,
>   };