[PATCH v4 2/5] of: reserved_mem: Accessor for acquiring reserved_mem

[Bjorn Andersson]

In some cases drivers referencing a reserved-memory region might want to
remap the entire region, but when defining the reserved-memory by "size"
the client driver has no means to know the associated base address of
the reserved memory region.

This patch adds an accessor for such drivers to acquire a handle to
their associated reserved-memory for this purpose.

A complicating factor for the implementation is that the reserved_mem
objects are created from the flattened DeviceTree, as such we can't
use the device_node address for comparison. Fortunately the name of the
node will be used as "name" of the reserved_mem and will be used when
building the full_name, so we can compare the "name" with the basename
of the full_name to find the match.

Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---

Changes since v3:
- Renamed function from _get() to _lookup()
- Picked up Rob's R-b

Changes since v2:
- None

Changes since v1:
- Previous patch provided interface to resolve memory-region reference, instead
  of direct lookup by device_node

 drivers/of/of_reserved_mem.c    | 26 ++++++++++++++++++++++++++
 include/linux/of_reserved_mem.h |  5 +++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index d507c3569a88..b108c7a1f74c 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -397,3 +397,29 @@ void of_reserved_mem_device_release(struct device *dev)
 	rmem->ops->device_release(rmem, dev);
 }
 EXPORT_SYMBOL_GPL(of_reserved_mem_device_release);
+
+/**
+ * of_reserved_mem_lookup() - acquire reserved_mem from a device node
+ * @np:		node pointer of the desired reserved-memory region
+ *
+ * This function allows drivers to acquire a reference to the reserved_mem
+ * struct based on a device node handle.
+ *
+ * Returns a reserved_mem reference, or NULL on error.
+ */
+struct reserved_mem *of_reserved_mem_lookup(struct device_node *np)
+{
+	const char *name;
+	int i;
+
+	if (!np->full_name)
+		return NULL;
+
+	name = kbasename(np->full_name);
+	for (i = 0; i < reserved_mem_count; i++)
+		if (!strcmp(reserved_mem[i].name, name))
+			return &reserved_mem[i];
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(of_reserved_mem_lookup);
diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
index f8e1992d6423..c58f780104f9 100644
--- a/include/linux/of_reserved_mem.h
+++ b/include/linux/of_reserved_mem.h
@@ -44,6 +44,7 @@ int early_init_dt_alloc_reserved_memory_arch(phys_addr_t size,
 void fdt_init_reserved_mem(void);
 void fdt_reserved_mem_save_node(unsigned long node, const char *uname,
 			       phys_addr_t base, phys_addr_t size);
+struct reserved_mem *of_reserved_mem_lookup(struct device_node *np);
 #else
 static inline int of_reserved_mem_device_init_by_idx(struct device *dev,
 					struct device_node *np, int idx)
@@ -55,6 +56,10 @@ static inline void of_reserved_mem_device_release(struct device *pdev) { }
 static inline void fdt_init_reserved_mem(void) { }
 static inline void fdt_reserved_mem_save_node(unsigned long node,
 		const char *uname, phys_addr_t base, phys_addr_t size) { }
+static inline struct reserved_mem *of_reserved_mem_lookup(struct device_node *np)
+{
+	return NULL;
+}
 #endif
 
 /**
-- 
2.12.0