Re: [PATCH v3 6/9] iommu/of: Introduce iommu_fwspec

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

On Tue, Jun 28, 2016 at 04:48:25PM +0100, Robin Murphy wrote:
> Introduce a common structure to hold the per-device firmware data that
> non-architectural IOMMU drivers generally need to keep track of.
> Initially this is DT-specific to complement the existing of_iommu
> support code, but will generalise further once other firmware methods
> (e.g. ACPI IORT) come along.
> 
> Ultimately the aim is to promote the fwspec to a first-class member of
> struct device, and handle the init/free automatically in the firmware
> code. That way we can have API calls look for dev->fwspec->iommu_ops
> before falling back to dev->bus->iommu_ops, and thus gracefully handle
> those troublesome multi-IOMMU systems which we currently cannot. To
> start with, though, make use of the existing archdata field and delegate
> the init/free to drivers to allow an incremental conversion rather than
> the impractical pain of trying to attempt everything in one go.
> 
> Suggested-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
> 
> v3: New.
> 
>  drivers/iommu/of_iommu.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_iommu.h | 18 ++++++++++++++++++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index 25406a8b9d4e..2b90c1f56ff2 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -220,3 +220,50 @@ void __init of_iommu_init(void)
>  				of_node_full_name(np));
>  	}
>  }
> +
> +int iommu_fwspec_init(struct device *dev, struct device_node *iommu_np)

These functions might want an of_* prefix to match the rest of the file,
or do you plan to re-use these later for ACPI?

> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
> index bd02b44902d0..5a4f516cfcfe 100644
> --- a/include/linux/of_iommu.h
> +++ b/include/linux/of_iommu.h
> @@ -15,6 +15,14 @@ extern void of_iommu_init(void);
>  extern const struct iommu_ops *of_iommu_configure(struct device *dev,
>  					struct device_node *master_np);
>  
> +struct iommu_fwspec {
> +	const struct iommu_ops	*iommu_ops;
> +	struct device_node	*iommu_np;
> +	void			*iommu_priv;
> +	unsigned int		num_ids;
> +	u32			ids[];
> +};
> +
>  #else
>  
>  static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
> @@ -31,8 +39,18 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
>  	return NULL;
>  }
>  
> +struct iommu_fwspec;
> +
>  #endif	/* CONFIG_OF_IOMMU */
>  
> +int iommu_fwspec_init(struct device *dev, struct device_node *iommu_np);
> +void iommu_fwspec_free(struct device *dev);
> +int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids);
> +static inline struct iommu_fwspec *dev_iommu_fwspec(struct device *dev)
> +{
> +	return dev->archdata.iommu;
> +}

I'm a bit nervous about putting this inline in a header file, since not
all architectures unconditionally provide the iommu field in dev_archdata.

Will