Am Freitag, 6. Januar 2006 21:23 schrieb Pete Zaitcev:
> On Fri, 6 Jan 2006 14:33:21 -0500 (EST), Alan Stern <[EMAIL PROTECTED]> wrote:
>
> > > > > is there any architecture for which packed is required in structures
> > > > > like this:
> > > > >
> > > > > /* All standard descriptors have these 2 fields at the beginning */
> > > > > struct usb_descriptor_header {
> > > > > __u8 bLength;
> > > > > __u8 bDescriptorType;
> > > > > };
> > > >
> > > > sizeof(struct usb_descriptor_header) will be 4 on ARM. If this
> > > > concerns you, you need to pack the structure thusly:
> > > >
> > > > struct usb_descriptor_header {
> > > > __u8 bLength;
> > > > __u8 bDescriptorType;
> > > > } __attribute__((packed));
> > >
> > > I had feared so. The usb include files are incorrect for arm in this case.
> > > Did I overdo it?
> >
> > Perhaps you are overreacting. Even though the total size of the structure
> > may be 4, I bet that bLength and bDescriptorType still occupy just the
> > first two bytes of the structure. Assuming this is so, there's nothing
> > wrong with the existing headers.
>
> Also, even if RMK is right, it either happens with some garbage gcc version
> or it is just a bug which didn't reach gcc people yet. It is dysfunctional
> to have structures padded in this way. On all other platforms they are
> only padded if they include a member which is bigger than the char.
> It is done to create properly aligned arrays of structures. This includes
> platforms without byte accesses like old Alpha.
>
> In this particular case it's moot, like Alan said. But even in general
> adding packed attribute usually is stupid and pandering to people building
> with hacked-up chains on 28-bit ARM or something. Why do we all have to
> suffer because of them? Screw that. Every case of ((packed)) has to have
> a very explicit justification.
Well,
in any case the file is inconsistent. Either all structures there have to
be packed or none. Unless someone can come up with something better
I am afraid an "#ifdef ARM" is needed. Comments?
Regards
Oliver
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