linux-kernel - Re: [PATCH v8 08/19] arm/xen: get_dma_ops: return xen_dma_ops if we are running as xen_initial

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Date:	Fri, 18 Oct 2013 16:48:47 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, konrad.wilk@...cle.com,
	Ian.Campbell@...rix.com, will.deacon@....com
Subject: Re: [PATCH v8 08/19] arm/xen: get_dma_ops: return xen_dma_ops if
	we are running as xen_initial_domain

On Fri, Oct 18, 2013 at 04:46:00PM +0100, Stefano Stabellini wrote:
> On Fri, 18 Oct 2013, Russell King - ARM Linux wrote:
> > On Fri, Oct 18, 2013 at 01:22:18PM +0100, Stefano Stabellini wrote:
> > > Russell,
> > > are you OK with this patch?
> > 
> > Only concern is why the change is soo large.
> > 
> > > > -static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> > > > +static inline struct dma_map_ops *__generic_dma_ops(struct device *dev)
> > > >  {
> > > >  	if (dev && dev->archdata.dma_ops)
> > > >  		return dev->archdata.dma_ops;
> > > >  	return &arm_dma_ops;
> > > >  }
> > > >  
> > > > +static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> > > > +{
> > > > +	if (xen_initial_domain())
> > > > +		return xen_dma_ops;
> > > > +	else
> > > > +		return __generic_dma_ops(dev);
> > > > +}
> > > > +
> > 
> > What's wrong with:
> > 
> >  static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> >  {
> > +	if (xen_initial_domain())
> > +		return xen_dma_ops;
> >  	if (dev && dev->archdata.dma_ops)
> >  		return dev->archdata.dma_ops;
> >  	return &arm_dma_ops;
> >  }
> 
> 
> xen_dma_ops functions might have to call back the native implementation.
> With the above there is no way for a xen_dma_ops function to get to
> archdata.dma_ops or arm_dma_ops.
> This is the reason why this patch introduces __generic_dma_ops.

Ah, that's fine then, but having that described in the commit message
would be useful.

Acked-by: Russell King <rmk+kernel@....linux.org.uk>

Thanks.
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