[PATCH v8 08/19] arm/xen: get_dma_ops: return xen_dma_ops if we are running as xen_initial_domain

[Stefano Stabellini]

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.