linux-kernel - Re: [PATCH] nvmem: u-boot-env: fix crc32 casting type

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Date:   Mon, 29 Aug 2022 08:25:58 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Rafał Miłecki <zajec5@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Tom Rini <trini@...sulko.com>,
        linux-arm-kernel@...ts.infradead.org, u-boot@...ts.denx.de,
        linux-kernel@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] nvmem: u-boot-env: fix crc32 casting type

Hello Rafał,

On 18.08.22 06:38, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@...ecki.pl>
> 
> This fixes:
> drivers/nvmem/u-boot-env.c:141:17: sparse: sparse: cast to restricted __le32
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Fixes: f955dc1445069 ("nvmem: add driver handling U-Boot environment variables")
> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> ---
>  drivers/nvmem/u-boot-env.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
> index 9b9abfb8f187..fb993ef4249f 100644
> --- a/drivers/nvmem/u-boot-env.c
> +++ b/drivers/nvmem/u-boot-env.c
> @@ -138,7 +138,7 @@ static int u_boot_env_parse(struct u_boot_env *priv)
>  		data_offset = offsetof(struct u_boot_env_image_redundant, data);
>  		break;
>  	}
> -	crc32 = le32_to_cpu(*(uint32_t *)(buf + crc32_offset));
> +	crc32 = le32_to_cpu(*(__le32 *)(buf + crc32_offset));

I had to do a double take to make sure alignment is not violated.
It's not, because crc32_offset is always zero.

How about rewriting this as

  /* CRC32 is always at offset 0 */
  crc32 = le32_to_cpup(buf);

To make the alignment clear to the reader?

>  	crc32_data_len = priv->mtd->size - crc32_data_offset;
>  	data_len = priv->mtd->size - data_offset;
>  

Cheers,
Ahmad

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