Subject: [PATCH v6 08/19] arm/xen: get_dma_ops: return xen_dma_ops if we are running on Xen

From: [email-masked] (Konrad Rzeszutek Wilk)
Date: Mon, 30 Sep 2013 11:17:12 -0400

On Fri, Sep 27, 2013 at 05:09:56PM +0100, Stefano Stabellini wrote:
> Signed-off-by: Stefano Stabellini <[email-masked]>
> Suggested-by: Catalin Marinas <[email-masked]>
> CC: will.deacon at arm.com
> CC: linux at arm.linux.org.uk

> ---
>  arch/arm/include/asm/dma-mapping.h |   13 ++++++++++++-
>  1 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/include/asm/dma-mapping.h b/arch/arm/include/asm/dma-mapping.h
> index 8807124..b638d6d 100644
> --- a/arch/arm/include/asm/dma-mapping.h
> +++ b/arch/arm/include/asm/dma-mapping.h
> @@ -12,17 +12,28 @@
>  #include <asm/memory.h>
>  #include <asm/cacheflush.h>
>  
> +#include <xen/xen.h>
> +#include <asm/xen/hypervisor.h>
> +
>  #define DMA_ERROR_CODE	(~0)
>  extern struct dma_map_ops arm_dma_ops;
>  extern struct dma_map_ops arm_coherent_dma_ops;
>  
> -static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> +static inline struct dma_map_ops *__get_dma_ops(struct device *dev)

How about calling it __generic_dma_ops ?

>  {
>  	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_domain())
> +		return xen_dma_ops;
> +	else
> +		return __get_dma_ops(dev);

Could you explan (hopefully in the git commit description) why
we cannot over-write arm_dma_ops with xen_dma_ops?

Thank you.

> +}
> +
>  static inline void set_dma_ops(struct device *dev, struct dma_map_ops *ops)
>  {
>  	BUG_ON(!dev);
> -- 
> 1.7.2.5
>