On Mon, 20 Jun 2011, Nicolas Pitre wrote:

On Mon, 20 Jun 2011, Alan Stern wrote:

quoted

On Mon, 20 Jun 2011, Nicolas Pitre wrote:

quoted

quoted

As far as I can tell, the other structures in ehci.h have 
((aligned(32)) simply in order to save space, since there can be large 
numbers of these structures allocated.

How can increasing the alignment to 32 bytes save space?

No, no -- the alignment is _decreased_ to 32 bits.  Without the 
attribute the alignment would have been 64 bits.

The aligned attribute requires a byte value not a bit value.
Maybe what you meant is ((aligned(4)) ?

Ah, very good point!  No, I meant ((aligned(32))).  Do "grep aligned 
drivers/usb/host/ehci.h" and you'll see.

So my understanding was wrong; these structure really are being forced 
to a strict alignment.  And indeed, now that I go back and look at the 
EHCI spec, it turns out that this alignment is required by the 
hardware.

Okay, so this digression was irrelevant to our discussion.  Forget I 
mentioned it...

Alan Stern