Re: [PATCH] USB: ehci: use packed,aligned(4) instead of removingthe packed attribute
From: Alan Stern
Date: Mon Jun 20 2011 - 17:05:24 EST
On Mon, 20 Jun 2011, Arnd Bergmann wrote:
> On Monday 20 June 2011 20:39:02 Alan Stern wrote:
> > On Mon, 20 Jun 2011, Alexander Holler wrote:
> > > I see it that way: packed is needed to be sure that at least for struct
> > > ehci_regs there are no padding bytes inbetween the members.
> > But is it really needed?
> No. When the structure is marked packed, it's broken because it relies
> on undefined behavior. If it's not packed, there is no problem.
> > > It might
> > > work without, but that depends on the compiler (-version, architecture,
> > > whatever).
> > Have there ever been any combinations of compiler, version,
> > architecture, whatever, that had unwanted padding bytes in this
> > structure?
> Only on compilers that are not able to build Linux kernels anyway.
Just as I thought. There's no reason to accept the proposed patch;
we're fine the way we are now.
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