On Nov 29, 2007 5:15 PM, Daniel Drake <[email protected]> wrote:
[...]
> To avoid the unaligned memory access, you would rewrite it as follows:
>
> void myfunc(u8 *data, u32 value)
> {
> [...]
> value = cpu_to_le32(value);
> put_unaligned(value, data);
> [...]
> }
>
> The get_unaligned() macro works similarly. Assuming 'data' is a pointer to
> memory and you wish to avoid unaligned access, its usage is as follows:
>
> u32 value = get_unaligned(data);
>
> These macros work work for memory accesses of any length (not just 32 bits as
> in the examples above). Be aware that when compared to standard access of
> aligned memory, using these macros to access unaligned memory can be costy in
> terms of performance.
>
The get_unaligned call above will not do what you intended given the,
at least as I read it, implied context of myfunc. Since data is a u8*
it will only get one byte of data. To avoid misunderstandings the code
should probably read:
u32 value = get_unaligned((u32 *)data);
/DM
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