Thread (64 messages) 64 messages, 7 authors, 2011-06-29

[PATCH] USB: ehci: use packed, aligned(4) instead of removing the packed attribute

From: nico@fluxnic.net (Nicolas Pitre)
Date: 2011-06-21 20:42:06
Also in: lkml

On Tue, 21 Jun 2011, Alan Stern wrote:
On Mon, 20 Jun 2011, Nicolas Pitre wrote:
quoted
quoted
We don't fall into any of these cases, and therefore as you say, we
don't need packed.  Arnd and I have both explained this.  So why do you 
keep arguing that we do need it?
Please show me where I keep arguing that you need it?
Not explicitly perhaps.  But you did write:
quoted
Doesn't mean that because it used to work that it is strictly correct.  
Wouldn't be the first time that a GCC upgrade broke the kernel because 
the kernel wasn't describing things properly enough.
which strongly implies that "packed" is needed.  You also wrote:
In this case ...
quoted
Yes, but that's a consequence of not being able to access those fields 
in their naturally aligned position anymore.  Hence the addition of the 
align attribute to tell the compiler that we know that the structure is 
still aligned to a certain degree letting the compiler to avoid 
byte-oriented instructions when possible.
which is predicated on the assumption that "packed" is needed.
... and also in this case, I was talking about proper use of the packed 
attribute in general, not at all about a specific case.  I wanted to 
provide a broader view to some people who expressed doubts and 
misunderstanding in the hope that the archive could keep this knowledge 
base available.

I apologize if that wasn't clear to you.


Nicolas
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