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Subject[PATCH] devres: Add devm_of_iomap()
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There are still quite a few cases where a device might want
to get to a different node of the device-tree, obtain the
resources and map them.

This is generally open coded in drivers which is quite error prone

We have of_iomap() and of_io_request_and_map() but they both
have shortcomings, such as not returning the size of the
resource found (which can be useful) and not being "managed".

This adds a devm_of_iomap() that provides all of these and
should probably replace uses of the above in most drivers.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
include/linux/device.h | 4 ++++
lib/devres.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+)

diff --git a/include/linux/device.h b/include/linux/device.h
index beabdbc08420..1529775ecb36 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -686,6 +686,10 @@ extern void devm_free_pages(struct device *dev, unsigned long addr);

void __iomem *devm_ioremap_resource(struct device *dev, struct resource *res);

+void __iomem *devm_of_iomap(struct device *dev,
+ struct device_node *node, int index,
+ resource_size_t *size);
+
/* allows to add/remove a custom action to devres stack */
int devm_add_action(struct device *dev, void (*action)(void *), void *data);
void devm_remove_action(struct device *dev, void (*action)(void *), void *data);
diff --git a/lib/devres.c b/lib/devres.c
index 78eca713b1d9..e320f80c1c4e 100644
--- a/lib/devres.c
+++ b/lib/devres.c
@@ -3,6 +3,7 @@
#include <linux/io.h>
#include <linux/gfp.h>
#include <linux/export.h>
+#include <linux/of_address.h>

void devm_ioremap_release(struct device *dev, void *res)
{
@@ -163,6 +164,41 @@ void __iomem *devm_ioremap_resource(struct device *dev, struct resource *res)
}
EXPORT_SYMBOL(devm_ioremap_resource);

+/*
+ * devm_of_iomap - Requests a resource and maps the memory mapped IO
+ * for a given device_node managed by a given device
+ *
+ * Checks that a resource is a valid memory region, requests the memory
+ * region and ioremaps it. All operations are managed and will be undone
+ * on driver detach of the device.
+ *
+ * This is to be used when a device requests/maps resources described
+ * by other device tree nodes (children or otherwise).
+ *
+ * @dev: The device "managing" the resource
+ * @node: The device-tree node where the resource resides
+ * @index: index of the MMIO range in the "reg" property
+ * @size: Returns the size of the resource (pass NULL if not needed)
+ * Returns a pointer to the requested and mapped memory or an ERR_PTR() encoded
+ * error code on failure. Usage example:
+ *
+ * base = devm_of_iomap(&pdev->dev, node, 0, NULL);
+ * if (IS_ERR(base))
+ * return PTR_ERR(base);
+ */
+void __iomem *devm_of_iomap(struct device *dev, struct device_node *node, int index,
+ resource_size_t *size)
+{
+ struct resource res;
+
+ if (of_address_to_resource(node, index, &res))
+ return IOMEM_ERR_PTR(-EINVAL);
+ if (size)
+ *size = resource_size(&res);
+ return devm_ioremap_resource(dev, &res);
+}
+EXPORT_SYMBOL(devm_of_iomap);
+
#ifdef CONFIG_HAS_IOPORT_MAP
/*
* Generic iomap devres
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