linux-kernel - Re: [PATCH v3] nvmem: u-boot-env: align endianness of crc32 values

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Message-ID: <d8e6135f837462a7f7cdf59e20bfc449@milecki.pl>
Date:   Mon, 13 Feb 2023 14:37:01 +0100
From:   Rafał Miłecki <rafal@...ecki.pl>
To:     INAGAKI Hiroshi <musashino.open@...il.com>
Cc:     srinivas.kandagatla@...aro.org, chunkeey@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] nvmem: u-boot-env: align endianness of crc32 values

On 2023-02-13 14:23, INAGAKI Hiroshi wrote:
> This patch fixes crc32 error on Big-Endianness system by conversion of
> calculated crc32 value.
> 
> Little-Endianness system:
> 
>   obtained crc32: Little
> calculated crc32: Little
> 
> Big-Endianness system:
> 
>   obtained crc32: Little
> calculated crc32: Big
> 
> log (APRESIA ApresiaLightGS120GT-SS, RTL8382M, Big-Endianness):
> 
> [    8.570000] u_boot_env
> 18001200.spi:flash@0:partitions:partition@...00: Invalid calculated
> CRC32: 0x88cd6f09 (expected: 0x096fcd88)
> [    8.580000] u_boot_env: probe of
> 18001200.spi:flash@0:partitions:partition@...00 failed with error -22
> 
> Fixes: f955dc144506 ("nvmem: add driver handling U-Boot environment 
> variables")
> 
> Signed-off-by: INAGAKI Hiroshi <musashino.open@...il.com>
> ---
> v2 -> v3
> 
> - fix sparse warning by using __le32 type and cpu_to_le32
> - fix character length of the short commit hash in "Fixes:" tag
> 
> v1 -> v2
> 
> - wrong fix for sparse warning due to misunderstanding
> - add missing "Fixes:" tag
> 
>  drivers/nvmem/u-boot-env.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvmem/u-boot-env.c b/drivers/nvmem/u-boot-env.c
> index 29b1d87a3c51..164bb04dfc3b 100644
> --- a/drivers/nvmem/u-boot-env.c
> +++ b/drivers/nvmem/u-boot-env.c
> @@ -117,8 +117,8 @@ static int u_boot_env_parse(struct u_boot_env 
> *priv)
>  	size_t crc32_offset;
>  	size_t data_offset;
>  	size_t data_len;
> -	uint32_t crc32;
> -	uint32_t calc;
> +	__le32 crc32;
> +	__le32 calc;
>  	size_t bytes;
>  	uint8_t *buf;
>  	int err;

This looks counter-intuitive to me, to store values on host system in
specified endianness. I'd say we should use __le32 type only to
represent numbers in device stored data (e.g. structs as processed by
device).

My suggesion: leave uint32_t for local variables and use le32_to_cpu().