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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