linux-kernel - Re: [PATCH 2/2] iommu: Add dummy implementations for !IOMMU

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Date:   Mon, 20 Mar 2017 20:14:31 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Mikko Perttunen <mperttunen@...dia.com>,
        iommu@...ts.linux-foundation.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iommu: Add dummy implementations for !IOMMU_IOVA

On Mon, Mar 20, 2017 at 08:11:28PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> Currently, building code which uses the API guarded by the IOMMU_IOVA
> will fail to link if IOMMU_IOVA is not enabled. Often this code will be
> using the API provided by the IOMMU_API Kconfig symbol, but support for
> this can be optional, with code falling back to contiguous memory. This
> commit implements dummy functions for the IOVA API so that it can be
> compiled out.
> 
> With both IOMMU_API and IOMMU_IOVA optional, code can now be built with
> or without support for IOMMU without having to resort to #ifdefs in the
> user code.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  include/linux/iova.h | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)

Hi Joerg,

I've got a series of patches that I'd like to merge for v4.12 that have
a build-time dependency on this patch. It would therefore be great to
get your Acked-by on this so that I can merge it through the DRM tree
with the rest of the patches. I can provide a stable branch with only
this patch for you to pull into the IOMMU tree.

Thierry

> diff --git a/include/linux/iova.h b/include/linux/iova.h
> index f27bb2c62fca..548982ad5f2f 100644
> --- a/include/linux/iova.h
> +++ b/include/linux/iova.h
> @@ -82,6 +82,7 @@ static inline unsigned long iova_pfn(struct iova_domain *iovad, dma_addr_t iova)
>  	return iova >> iova_shift(iovad);
>  }
>  
> +#ifdef CONFIG_IOMMU_IOVA
>  int iova_cache_get(void);
>  void iova_cache_put(void);
>  
> @@ -106,5 +107,95 @@ void put_iova_domain(struct iova_domain *iovad);
>  struct iova *split_and_remove_iova(struct iova_domain *iovad,
>  	struct iova *iova, unsigned long pfn_lo, unsigned long pfn_hi);
>  void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain *iovad);
> +#else
> +static inline int iova_cache_get(void)
> +{
> +	return -ENOTSUPP;
> +}
> +
> +static inline void iova_cache_put(void)
> +{
> +}
> +
> +static inline struct iova *alloc_iova_mem(void)
> +{
> +	return NULL;
> +}
> +
> +static inline void free_iova_mem(struct iova *iova)
> +{
> +}
> +
> +static inline void free_iova(struct iova_domain *iovad, unsigned long pfn)
> +{
> +}
> +
> +static inline void __free_iova(struct iova_domain *iovad, struct iova *iova)
> +{
> +}
> +
> +static inline struct iova *alloc_iova(struct iova_domain *iovad,
> +				      unsigned long size,
> +				      unsigned long limit_pfn,
> +				      bool size_aligned)
> +{
> +	return NULL;
> +}
> +
> +static inline void free_iova_fast(struct iova_domain *iovad,
> +				  unsigned long pfn,
> +				  unsigned long size)
> +{
> +}
> +
> +static inline unsigned long alloc_iova_fast(struct iova_domain *iovad,
> +					    unsigned long size,
> +					    unsigned long limit_pfn)
> +{
> +	return 0;
> +}
> +
> +static inline struct iova *reserve_iova(struct iova_domain *iovad,
> +					unsigned long pfn_lo,
> +					unsigned long pfn_hi)
> +{
> +	return NULL;
> +}
> +
> +static inline void copy_reserved_iova(struct iova_domain *from,
> +				      struct iova_domain *to)
> +{
> +}
> +
> +static inline void init_iova_domain(struct iova_domain *iovad,
> +				    unsigned long granule,
> +				    unsigned long start_pfn,
> +				    unsigned long pfn_32bit)
> +{
> +}
> +
> +static inline struct iova *find_iova(struct iova_domain *iovad,
> +				     unsigned long pfn)
> +{
> +	return NULL;
> +}
> +
> +static inline void put_iova_domain(struct iova_domain *iovad)
> +{
> +}
> +
> +static inline struct iova *split_and_remove_iova(struct iova_domain *iovad,
> +						 struct iova *iova,
> +						 unsigned long pfn_lo,
> +						 unsigned long pfn_hi)
> +{
> +	return NULL;
> +}
> +
> +static inline void free_cpu_cached_iovas(unsigned int cpu,
> +					 struct iova_domain *iovad)
> +{
> +}
> +#endif
>  
>  #endif
> -- 
> 2.12.0
> 

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