Re: [GIT] Sparc

[David Miller]

From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Thu, 5 Nov 2015 16:43:52 -0800

> On Thu, Nov 5, 2015 at 1:39 PM, David Miller <davem@xxxxxxxxxxxxx> wrote:
>>
>> 5) Fix iommu-common code so it doesn't emit rediculous warnings
>>    on some architectures, particularly ARM.
> 
> Heh. So looking at that patch, I can't but help to react that this:
> 
>   #define IOMMU_ERROR_CODE       (~(unsigned long) 0)
> 
> is still pretty ridiculous.  Maybe just (-1ul), or for those people
> who don't understand C unsigned long arithmetic and think that a
> negative unsigned long looks odd, (~0ul)?

Yeah I struggled with this, believe it or not.

The expression causing the problem was (~(dma_addr_t) 0) (AKA
DMA_ERROR_CODE) being used as the return value.

So I just replicated that expression.  A neuron did fire saying "hey
pinhead, why not just use ~0UL" but I did not listen to the little
voice in my head this time.
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