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SubjectRe: I need help with a sparse warning
Roland Dreier wrote:
> > In file drivers/net/wireless/p54/p54common.c, the statement
> >
> > priv->rx_mtu = (size_t) le16_to_cpu((__le16)bootrec->data[10]);
>
> [I don't see this code in Linus's tree]

It is in wireless-testing.

>
> the code in question looks buggy to me. Since bootrec->data[10] is u32,
> casting it to a 16-bit type is going to take a different 2 bytes out of
> the 4 bytes depending on the endianness of the system the driver is
> built for. And I assume you are parsing some fixed-layout thing that
> the firmware is giving you or something like that.
>
> I would guess you want something like:
>
> priv->rx_mtu = le16_to_cpu(((__force __le16 *) bootrec->data)[20]);
>
> (__force is what shuts up sparse, and as far as I can see, the size_t
> cast is useless, since the result will be promoted anyway)

Yes, that one works. As you suspected, this section is parsing data
from the firmware.

When I started, there were 18 sparse warnings, and a number of them
were accesses of little-endian variables without an appropriate
leXX_to_cpu() conversion. Obviously, this code has never been tested
on a big-endian machine.

Thanks,

Larry



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