Re: [PATCH v10 2/3] block: change annotation of rdb_CylBlocks in affs_hardblocks.h

[Christoph Hellwig <hch@lst.de>]

On Fri, Jun 16, 2023 at 07:20:52PM +1200, Michael Schmitz wrote:
> Am 16.06.2023 um 17:48 schrieb Christoph Hellwig:
>> On Fri, Jun 16, 2023 at 07:53:11AM +1200, Michael Schmitz wrote:
>>> Thanks - now there's two __s32 fields in that header - one checksum each
>>> for RDB and PB. No one has so far seen the need for a 'signed big endian 32
>>> bit' type, and I'd rather avoid adding one to types.h. I'll leave those as
>>> they are (with the tacit understanding that they are equally meant to be
>>> big endian).
>>
>> We have those in a few other pleases and store them as __be32 as well.  The
>> (implicit) cast to s32 will make them signed again.
>
> Where's that cast to s32 hidden? I've only seen
>
> #define __be32_to_cpu(x) ((__force __u32)(__be32)(x))
>
> which would make the checksums unsigned if __be32 was used.
>
> Whether the checksum code uses signed or unsigned math would require 
> inspection of the Amiga partitioning tool source which I don't have, so 
> I've kept __s32 to be safe.

Well, the return value of be32_to_cpu is going to be a assigned to a,
presumably signed, variable.  With that you get an implicit cast.