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Subject: Re: [PATCH v2 2/9] dmapool: cleanup error messages
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From: Tony Battersby <tonyb@cybernetics.com>
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Date: Fri, 3 Aug 2018 13:03:17 -0400
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To: Matthew Wilcox <willy@infradead.org>, Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Marek Szyprowski <m.szyprowski@samsung.com>, Sathya Prakash <sathya.prakash@broadcom.com>, Chaitra P B <chaitra.basappa@broadcom.com>, Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>, iommu@lists.linux-foundation.org, linux-mm <linux-mm@kvack.org>, linux-scsi <linux-scsi@vger.kernel.org>, MPT-FusionLinux.pdl@broadcom.com

On 08/03/2018 12:22 PM, Matthew Wilcox wrote:
> On Fri, Aug 03, 2018 at 06:59:20PM +0300, Andy Shevchenko wrote:
>>>>> I'm pretty sure this was created in an order to avoid bad looking (and
>>>>> in some cases frightening) "NULL device *" part.
>> JFYI: git log --no-merges --grep 'NULL device \*'
> I think those commits actually argue in favour of Tony's patch to remove
> the special casing.  Is it really useful to create dma pools with a NULL
> device?
>
>
dma_alloc_coherent() does appear to support a NULL dev, so it might make
sense in theory.A  But I can't find any in-tree callers that actually
pass a NULL dev to dma_pool_create().A  So for one of the dreaded (NULL
device *) messages to show up, it would take both a new caller that
passes a NULL dev to dma_pool_create() and a bug to cause the message to
be printed.A  Is that worth the special casing?