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Re: I need help with a sparse warning

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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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