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

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Date:   Fri, 17 Feb 2023 18:30:24 +0100
From:   Christian Lamparter <chunkeey@...il.com>
To:     Rafał Miłecki <rafal@...ecki.pl>,
        INAGAKI Hiroshi <musashino.open@...il.com>
Cc:     srinivas.kandagatla@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] nvmem: u-boot-env: align endianness of crc32 values

On 2/13/23 14:37, Rafał Miłecki wrote:
> 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().

Hmm, this is strange. The kernel's u-boot-env driver works without any
additional changes in the le<->be department on the Big-Endian
PowerPC APM82181 WD MyBook Live NAS.

Is there something odd going on with the WD MyBook Live, or is it
the APRESIA ApresiaLightGS120GT-SS that is special?

Regards,
Christian