Re: [PATCH v6 1/8] iommu: provide early initialisation hook for IOMMU drivers

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

On Thu, Dec 04, 2014 at 11:25:35AM +0000, Grant Likely wrote:
> On Thu, Dec 4, 2014 at 11:19 AM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
> > On Thursday 04 December 2014 10:21:27 Will Deacon wrote:
> >> > > Sure, I'll add this to my list of stuff to do for 3.20.
> >> >
> >> > Does that mean the we don't get any of the patches for 3.19 despite the
> >> > Acks?
> >>
> >> Hmm, I don't know how useful they are without the get/set ops and I don't
> >> think I can get those ready for 3.19 given where we currently are.
> >>
> >> Grant's suggestion of adding an iommu_ops pointer to device_node would work
> >> as a temporary hack, but anything more advanced is going to need proper
> >> review.
> >
> > Right. I guess it doesn't hurt much if we put the new pointer inside
> > #ifdef CONFIG_OF_IOMMU, then at least there is no significant size
> > increase in most DT based platforms.
> 
> Yes, I can live with that hack on the proviso that it will be removed by v3.20
> 
> Oh, and please put an ugly /* */ comment block in the #ifdef
> CONFIG_OF_IOMMU section that makes it really clear that it is an ugly
> hack and will be removed in the next release. I don't want anyone
> getting ideas that adding pointers to struct device_node is a good
> idea.

Something like the mess below?

Will

--->8

diff --git a/include/linux/of.h b/include/linux/of.h
index 29f0adc5f3e4..6f85c02bc1a6 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -43,6 +43,9 @@ struct property {
 #if defined(CONFIG_SPARC)
 struct of_irq_controller;
 #endif
+#ifdef CONFIG_OF_IOMMU
+struct iommu_ops;
+#endif
 
 struct device_node {
 	const char *name;
@@ -65,6 +68,19 @@ struct device_node {
 	unsigned int unique_id;
 	struct of_irq_controller *irq_trans;
 #endif
+#ifdef CONFIG_OF_IOMMU
+/*
+ * HACK! HACK! HACK!
+ *
+ * This is a temporary hack to associate a device_node for an
+ * IOMMU with its set of iommu_ops so that we can probe its upstream DMA
+ * masters on the platform bus by parsing the "iommus" property directly.
+ *
+ * This is going away in 3.20. Please use the of_iommu_{get,set}_ops
+ * functions to get hold of this data.
+ */
+	struct iommu_ops *__iommu_ops_use_accessors;
+#endif
 };
 
 #define MAX_PHANDLE_ARGS 16
diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
index d03abbb11c34..392ec5f212db 100644
--- a/include/linux/of_iommu.h
+++ b/include/linux/of_iommu.h
@@ -14,6 +14,17 @@ extern int of_get_dma_window(struct device_node *dn, const char *prefix,
 extern void of_iommu_init(void);
 extern struct iommu_ops *of_iommu_configure(struct device *dev);
 
+static inline void of_iommu_set_ops(struct device_node *np,
+				    const struct iommu_ops *ops)
+{
+	np->__iommu_ops_use_accessors = ops;
+}
+
+static inline struct iommu_ops *of_iommu_get_ops(struct device_node *np)
+{
+	return np->__iommu_ops_use_accessors;
+}
+
 #else
 
 static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
@@ -29,19 +40,15 @@ static inline struct iommu_ops *of_iommu_configure(struct device *dev)
 	return NULL;
 }
 
-#endif	/* CONFIG_OF_IOMMU */
-
 static inline void of_iommu_set_ops(struct device_node *np,
-				    const struct iommu_ops *ops)
-{
-	np->data = (struct iommu_ops *)ops;
-}
-
+				    const struct iommu_ops *ops) { }
 static inline struct iommu_ops *of_iommu_get_ops(struct device_node *np)
 {
-	return np->data;
+	return NULL;
 }
 
+#endif	/* CONFIG_OF_IOMMU */
+
 extern struct of_device_id __iommu_of_table;
 
 typedef int (*of_iommu_init_fn)(struct device_node *);