Re: drivers/block/ub.c

[Oliver Neukum <oliver@neukum.org>]

Am Samstag, 26. Juni 2004 23:41 schrieb David S. Miller:
> On Sat, 26 Jun 2004 22:35:15 +0200
> Oliver Neukum <oliver@neukum.org> wrote:
> 
> > 
> > > +/* command block wrapper */
> > > +struct bulk_cb_wrap {
> > > +	u32	Signature;		/* contains 'USBC' */
> > > +	u32	Tag;			/* unique per command id */
> > > +	u32	DataTransferLength;	/* size of data */
> > > +	u8	Flags;			/* direction in bit 0 */
> > > +	u8	Lun;			/* LUN normally 0 */
> > > +	u8	Length;			/* of of the CDB */
> > > +	u8	CDB[MAX_CDB_SIZE];	/* max command */
> > > +};
> > 
> > should be packed attributed
> 
> Only when necessary, and I do not belive any platform Linux supports
> needs it in this case.
> 
> Packed attributing is _BAD_ when it isn't needed because it forces GCC
> to output multiple byte-sized loads in order to access larger than
> byte-sized elements because it cannot assume the proper alignment on RISC
> systems.

Unless I am mistaken, this structure is transfered as such over the bus,
so IMHO here it is needed.

	Regards
		Oliver