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Date:   Tue, 6 Oct 2020 08:57:49 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Leon Romanovsky <leon@kernel.org>
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Subject: Re: [PATCH rdma-next v2] RDMA: Explicitly pass in the dma_device to
 ib_register_device
Message-ID: <20201006075749.GA23345@infradead.org>
References: <20201006073229.2347811-1-leon@kernel.org>
 <20201006073554.GA16894@infradead.org>
 <20201006075345.GK1874917@unreal>
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On Tue, Oct 06, 2020 at 10:53:45AM +0300, Leon Romanovsky wrote:
> On Tue, Oct 06, 2020 at 08:35:54AM +0100, Christoph Hellwig wrote:
> > > +	WARN_ON(!IS_ENABLED(CONFIG_DMA_VIRT_OPS) && !dma_device);
> > > +	if (!dma_device) {
> > >  		/*
> > > -		 * The caller did not provide custom DMA operations. Use the
> > > -		 * DMA mapping operations of the parent device.
> > > +		 * If the caller does not provide a DMA capable device then the
> > > +		 * IB device will be used. In this case the caller should fully
> > > +		 * setup the ibdev for DMA. This usually means using
> > > +		 * dma_virt_ops.
> > >  		 */
> > > +		device->dev.dma_ops = &dma_virt_ops;
> > > +		dma_device = &device->dev;
> >
> > The lack of the if probably means this will fail to link now when
> > CONFIG_DMA_VIRT_OPS is not set.  This also seems to not remove the
> > dma_virt_ops assignment in the callers.
> 
> I expect to see this during driver development/testing. It is not worth
> to make if() case id device won't be operable.

Then you'll need an ifdef or whatever your preferred method is to
avoid the dma_virt_ops symbol reference for the !CONFIG_DMA_VIRT_OPS
case.