From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH] swiotlb: swiotlb_{alloc,free}_buffer should depend on
	CONFIG_DMA_DIRECT_OPS
Date: Sat, 24 Mar 2018 18:03:51 +0100
Message-ID: <20180324170351.GA511@lst.de>
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	<20180323185707.GD25533@char.us.oracle.com>
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To: Konrad Rzeszutek Wilk <konrad.wilk-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Cc: tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
List-Id: iommu@lists.linux-foundation.org

On Fri, Mar 23, 2018 at 02:57:07PM -0400, Konrad Rzeszutek Wilk wrote:
> On Fri, Mar 23, 2018 at 06:49:30PM +0100, Christoph Hellwig wrote:
> > Otherwise we might get unused symbol warnings for configs that built
> > swiotlb.c only for use by xen-swiotlb.c and that don't otherwise select
> > CONFIG_DMA_DIRECT_OPS, which is possible on arm.
> > 
> > Fixes: 16e73adbca76 ("dma/swiotlb: Remove swiotlb_{alloc,free}_coherent()")
> > Reported-by: Stephen Rothwell <sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org>
> > Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> 
> 
> Alternatively could we set the Kconfig to slect DMA_DIRECT_OPS?


IFF we build swiotlb.c only for xen-swiotlb we don't need DMA_DIRECT_OPS.
IF you are fine with just requring it as well that would be doable nicely
only if we consolidate to a single defintion of CONFIG_SWIOTLB instead
of one per architecture.  Which is something we should do anyway,
so I'll look into it once I get some time.