[v9.1] of: Provide function to request and map memory

Commit Message

Matthias Brugger June 20, 2014, 12:28 p.m. UTC

A call to of_iomap does not request the memory region.
This patch adds the function of_io_request_and_map which requests
the memory region before mapping it.

Signed-off-by: Matthias Brugger <[e-mail]>
Suggested-by: Thomas Gleixner <[e-mail]>
Suggested-by: Rob Herring <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
---
Changes for v9.1:
- fixed the Author email address

 drivers/of/address.c       |   29 +++++++++++++++++++++++++++++
 include/linux/of_address.h |    8 ++++++++
 2 files changed, 37 insertions(+)

Comments

Russell King - ARM Linux June 20, 2014, 4 p.m. UTC | #1

On Fri, Jun 20, 2014 at 02:28:48PM +0200, Matthias Brugger wrote:
> +/*
> + * of_io_request_and_map - Requests a resource and maps the memory mapped IO
> + *			   for a given device_node
> + * @device:	the device whose io range will be mapped
> + * @index:	index of the io range
> + * @name:	name of the resource
> + *
> + * Returns a pointer to the requested and mapped memory
> + */
> +void __iomem *of_io_request_and_map(struct device_node *np, int index,
> +					char *name)
> +{
> +	struct resource res;
> +	void __iomem *mem;
> +
> +	if (of_address_to_resource(np, index, &res))
> +		return NULL;
> +
> +	if (!request_mem_region(res.start, resource_size(&res), name))
> +		return NULL;
> +
> +	mem = ioremap(res.start, resource_size(&res));
> +	if (!mem)
> +		release_mem_region(res.start, resource_size(&res));

We did this "return NULL" approach for devm_request_and_ioremap(), and
ended up not liking the number of drivers returning random error codes
on failure (despite the proper return code being documented.)  It's
worth reading the commit text for the commit introducing
devm_ioremap_resource() which replaces devm_request_and_ioremap():

commit 75096579c3ac39ddc2f8b0d9a8924eba31f4d920
Author: Thierry Reding <[e-mail]>
Date:   Mon Jan 21 11:08:54 2013 +0100

    lib: devres: Introduce devm_ioremap_resource()

which may help avoid repeating the same mistakes here.

Patch

diff --git a/drivers/of/address.c b/drivers/of/address.c
index cb4242a..09074ba 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -721,3 +721,32 @@  void __iomem *of_iomap(struct device_node *np, int index)
 	return ioremap(res.start, resource_size(&res));
 }
 EXPORT_SYMBOL(of_iomap);
+
+/*
+ * of_io_request_and_map - Requests a resource and maps the memory mapped IO
+ *			   for a given device_node
+ * @device:	the device whose io range will be mapped
+ * @index:	index of the io range
+ * @name:	name of the resource
+ *
+ * Returns a pointer to the requested and mapped memory
+ */
+void __iomem *of_io_request_and_map(struct device_node *np, int index,
+					char *name)
+{
+	struct resource res;
+	void __iomem *mem;
+
+	if (of_address_to_resource(np, index, &res))
+		return NULL;
+
+	if (!request_mem_region(res.start, resource_size(&res), name))
+		return NULL;
+
+	mem = ioremap(res.start, resource_size(&res));
+	if (!mem)
+		release_mem_region(res.start, resource_size(&res));
+
+	return mem;
+}
+EXPORT_SYMBOL(of_io_request_and_map);
diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 5f6ed6b..725b875 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -96,6 +96,8 @@  static inline struct of_pci_range *of_pci_range_parser_one(
 extern int of_address_to_resource(struct device_node *dev, int index,
 				  struct resource *r);
 void __iomem *of_iomap(struct device_node *node, int index);
+void __iomem *of_io_request_and_map(struct device_node *device,
+					int index, char *name);
 #else
 static inline int of_address_to_resource(struct device_node *dev, int index,
 					 struct resource *r)
@@ -107,6 +109,12 @@  static inline void __iomem *of_iomap(struct device_node *device, int index)
 {
 	return NULL;
 }
+
+static inline void __iomem *of_io_request_and_map(struct device_node *device,
+					int index, char *name)
+{
+	return NULL;
+}
 #endif
 
 #if defined(CONFIG_OF_ADDRESS) && defined(CONFIG_PCI)