From: Sven Eckelmann

Sent: 24 July 2021 17:24

Sparse will try to check casting of simple integer types which are marked
as __bitwise. This for example "disallows" simple casting of __be{16,32,64}
or __le{16,32,64} to other types. This is also true for pointers to
variables with this type.

But the new generic {get,put}_unaligned is doing that by (reinterpret)
casting the original pointer to a new (anonymous) struct pointer. This will
then create warnings like:

  net/batman-adv/distributed-arp-table.c:1461:19: warning: cast from restricted __be32 *
  net/batman-adv/distributed-arp-table.c:1510:23: warning: cast from restricted __be32 [usertype]
*[assigned] magic
  net/batman-adv/distributed-arp-table.c:1588:24: warning: cast from restricted __be32 [usertype]
*[assigned] yiaddr

The special attribute force must be used in such statements when the cast
is known to be safe to avoid these warnings.

At least the __force is being added to an existing cast.

The real problems are when a (__force __le32)value cast is used
to silence sparse.
These should really be something like:
	__tell_sparce(__le32, value)
so that the whole thing can be removed by the preprocessor when
compiling the code.

	David

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