On 25/07/16 16:41, Lorenzo Pieralisi wrote:
[...]

quoted

quoted

diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index 308791f..2362232 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h

@@ -15,13 +15,8 @@ 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[];
-};
+void of_iommu_set_ops(struct device_node *np, const struct iommu_ops *ops);
+const struct iommu_ops *of_iommu_get_ops(struct device_node *np);

Is there some reason we need to retain the existing definitions of
these? I was assuming we'd be able to move the entire implementation
over to the fwspec code and leave behind nothing more than trivial
wrappers, e.g.:

#define of_iommu_get_ops(np) iommu_fwspec_get_ops(&(np)->fwnode_handle)

Yep, that's exactly what I did but then I was bitten by config
dependencies. If we implement of_iommu_get/set_ops() as wrappers,
we have to compile iommu_fwspec_get/set_ops() on arches that may
not have struct dev_archdata.iommu, unless we introduce yet another
config symbol to avoid compiling that code (see eg iommu_fwspec_init(),
we can't compile it on eg x86 even though we do need of_iommu_get_ops()
on it - so iommu_fwspec_get_ops(), that lives in the same compilation
unit as eg iommu_fwspec_init()).

So short answer is: there is no reason apart from dev_archdata.iommu
being arch specific, if we were able to move iommu_fwspec to generic
code (ie struct device, somehow) I would certainly get rid of this
stupid code duplication (or as I said I can add a config entry for
that, more ideas are welcome).

OK, given Rob's comment as well, I guess breaking that dependency is to
everyone's benefit. Since it's quite closely related, how about if we
follow the arch_setup_dma_ops() pattern with an
arch_{get,set}_iommu_fwspec(dev) type thing?

Robin.

Thanks,
Lorenzo

quoted

Robin.

quoted

 #else
 

@@ -39,17 +34,14 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
 	return NULL;
 }
 
-struct iommu_fwspec;
-
-#endif	/* CONFIG_OF_IOMMU */
+static inline void of_iommu_set_ops(struct device_node *np,
+				    const struct iommu_ops *ops)
+{ }
 
-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);
-struct iommu_fwspec *dev_iommu_fwspec(struct device *dev);
+static inline const struct iommu_ops *
+of_iommu_get_ops(struct device_node *np) { return NULL; }
 
-void of_iommu_set_ops(struct device_node *np, const struct iommu_ops *ops);
-const struct iommu_ops *of_iommu_get_ops(struct device_node *np);
+#endif	/* CONFIG_OF_IOMMU */
 
 extern struct of_device_id __iommu_of_table;