From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 2/5] dma-mapping: move the dma_coherent flag to struct
	device
Date: Tue, 11 Sep 2018 08:46:36 +0200
Message-ID: <20180911064636.GA6214@lst.de>
References: <20180910060533.27172-1-hch@lst.de>
	<20180910060533.27172-3-hch@lst.de>
	<20180910161350.GA10380@kroah.com>
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To: Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
Cc: linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org, Paul Burton <paul.burton-8NJIiSa5LzA@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
List-Id: iommu@lists.linux-foundation.org

On Mon, Sep 10, 2018 at 06:13:50PM +0200, Greg Kroah-Hartman wrote:
> > +#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
> > +    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
> > +    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
> > +	bool			dma_coherent:1;
> > +#endif
> 
> It's just one bit, why not always have it enabled here?  If the arch
> uses it or doesn't, no big deal.
> 
> Or are you using this to "catch" arches that mess something up?

Yes, that is the intent - I don't want architectures to accidentally
set it while not selecting the non-coherent infrastructure, as it
won't have an effect.