> From: Of Hans de Goede
>
> The iu struct definitions are usb packet definitions, so no alignment should
> happen. Notice that assuming 32 bit alignment this does not make any
> difference at all.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> include/linux/usb/uas.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/usb/uas.h b/include/linux/usb/uas.h
> index 772b66b..3fc8e8b 100644
> --- a/include/linux/usb/uas.h
> +++ b/include/linux/usb/uas.h
> @@ -9,7 +9,7 @@ struct iu {
> __u8 iu_id;
> __u8 rsvd1;
> __be16 tag;
> -};
> +} __attribute__((__packed__));
Won't this cause the compiler to generate multiple byte accesses
for the 'tag' field in systems that don't support misaligned
accesses.
I'd have thought that 'packed' should only be specified on structures
that are likely to be misaligned in memory.
The memory for usb packets should probably be 4 byte aligned (at least)
for dma efficiency.
(Unless they contain ethernet frames when you want 4n+2 alignment).
David
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