Hi,
It seems to be the conversion to a pointer and back that makes
le16_to_cpus to loose the __attribute__((packed)). In my opinion
the compiler should warn that it discards the attribute.
I suspect it does something wrong on other architectures too, but most
support non aligned access. I used gcc-3.4.3 for this tests.
The following is what the preprocessor makes from le16_to_cpus.
static __inline__ void __swab16s(__u16 *addr)
{
do { *( addr ) = ({ __u16 __tmp = ( *( ( addr ) ) ) ;
({ __u16 __x = ( __tmp ); ((__u16)( (((__u16)(__x) & (__u16)0x00ffU) <<
8)
| (((__u16)(__x) & (__u16)0xff00U) >> 8) )); }) ; }) ; } while (0) ;
}
I found no way to convince the compiler to keep the attribute packed when a
pointer is used:
struct TEST {
char x;
short y;
} __attribute__((packed));
void testfunc(TEST *test) {
(test->y) = ___swab16(test->y); // is working correctly
(*&test->y) == ___swab16(*&test->y); // does discard
__attribute__((packed))
}
So my proposal is to avoid the call of the macro with a pointer. The
following
is tested to work correctly:
hub->descriptor->wHubCharacteristics=le16_to_cpu(hub->descriptor->wHubCharac
teristics);
Jochen
> > Under Big Endian ARM linux-2.6.11.12 the following code from
usb/core/hub.c
> > triggers an alignment exception:
> >
> > le16_to_cpus(&hub->descriptor->wHubCharacteristics); /* This triggers
two
> > alignment exceptions */
> struct usb_hub_descriptor {
> __u8 bDescLength;
> __u8 bDescriptorType;
> __u8 bNbrPorts;
> __u16 wHubCharacteristics;
> .....
> } __attribute__ ((packed));
>
> As you can see the structure is declared packed. This should work. Either
> the macro or the compiler are at fault.
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