Re: [PATCH V2 3/3] ethernet: Convert mac address uses of 6 to ETH_ALEN

From: Olof Johansson
Date: Thu Aug 01 2013 - 17:24:37 EST

On Thu, Aug 1, 2013 at 2:10 PM, David Miller <davem@xxxxxxxxxxxxx> wrote:
> From: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
> Date: Thu, 1 Aug 2013 22:06:18 +0100
>> On Thu, Aug 01, 2013 at 02:04:47PM -0700, Joe Perches wrote:
>>> On Thu, 2013-08-01 at 21:58 +0100, Russell King - ARM Linux wrote:
>>> > This seems rather obscure - I mean, it's not obvious to driver authors
>>> > that should be the case. Would it not be better to make this a little
>>> > more obvious somehow? Maybe __aligned(2) against mac_addr? Or
>>> > maybe have a debugging check for it?
>>> That'd be for David Miller (cc'd).
>>> I believe he's argued in the past that any alignment check
>>> for mac addresses was unnecessary.
>>> For all I know it really might not matter because pasemi
>>> can successfully dereference a ushort against an odd char
>>> pointer.
>>> I just noticed it and thought it'd be better moved.
>> As can ARM too for years now - either in hardware or via fixup for
>> kernel code.
> But probably not a good idea if it's done in a fast path.

This particular driver is for the PA Semi chips, and I very much doubt
that compatible hardware will ever show up anywhere else; they're
fairly dependent on the I/O architecture of the chip and Apple has not
brought those aspects forward in their ARM chips, as far as I know.

So, you might as well leave the code alone for now. It's not used on
fast path, and the system definitely handles unaligned accesses for
this -- it has for years already.

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