[PATCH 1/2] resource: Add device-managed request/release_resource()

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

Provide device-managed implementations of the request_resource() and
release_resource() functions. Upon failure to request a resource, the
new devm_request_resource() function will output an error message for
consistent error reporting.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 Documentation/driver-model/devres.txt |  2 +
 include/linux/ioport.h                |  5 +++
 kernel/resource.c                     | 73 +++++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+)

diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index 034d32b00846..b466f3d19bcb 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -252,6 +252,8 @@ IIO
   devm_iio_device_unregister()
 
 IO region
+  devm_request_resource()
+  devm_release_resource()
   devm_request_region()
   devm_request_mem_region()
   devm_release_region()
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 142ec544167c..2c5250222278 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -215,6 +215,11 @@ static inline int __deprecated check_region(resource_size_t s,
 
 /* Wrappers for managed devices */
 struct device;
+
+extern int devm_request_resource(struct device *dev, struct resource *root,
+				 struct resource *new);
+extern void devm_release_resource(struct device *dev, struct resource *new);
+
 #define devm_request_region(dev,start,n,name) \
 	__devm_request_region(dev, &ioport_resource, (start), (n), (name))
 #define devm_request_mem_region(dev,start,n,name) \
diff --git a/kernel/resource.c b/kernel/resource.c
index da14b8d09296..39d99aa401a6 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1248,6 +1248,79 @@ int release_mem_region_adjustable(struct resource *parent,
 /*
  * Managed region resource
  */
+static void devm_resource_release(struct device *dev, void *ptr)
+{
+	struct resource **r = ptr;
+
+	release_resource(*r);
+}
+
+/**
+ * devm_request_resource() - request and reserve an I/O or memory resource
+ * @dev: device for which to request the resource
+ * @root: root of the resource tree from which to request the resource
+ * @new: descriptor of the resource to request
+ *
+ * This is a device-managed version of request_resource(). There is usually
+ * no need to release resources requested by this function explicitly since
+ * that will be taken care of when the device is unbound from its driver.
+ * If for some reason the resource needs to be released explicitly, because
+ * of ordering issues for example, drivers must call devm_release_resource()
+ * rather than the regular release_resource().
+ *
+ * When a conflict is detected between any existing resources and the newly
+ * requested resource, an error message will be printed.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int devm_request_resource(struct device *dev, struct resource *root,
+			  struct resource *new)
+{
+	struct resource *conflict, **ptr;
+
+	ptr = devres_alloc(devm_resource_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	*ptr = new;
+
+	conflict = request_resource_conflict(root, new);
+	if (!conflict) {
+		devres_add(dev, ptr);
+		return 0;
+	}
+
+	dev_err(dev, "resource collision: %pR conflicts with %s %pR\n", new,
+		conflict->name, conflict);
+	devres_free(ptr);
+	return -EBUSY;
+}
+EXPORT_SYMBOL(devm_request_resource);
+
+static int devm_resource_match(struct device *dev, void *res, void *data)
+{
+	struct resource **ptr = res;
+
+	if (WARN_ON(!ptr || !*ptr))
+		return 0;
+
+	return *ptr == data;
+}
+
+/**
+ * devm_release_resource() - release a previously requested resource
+ * @dev: device for which to release the resource
+ * @new: descriptor of the resource to release
+ *
+ * Releases a resource previously requested using devm_request_resource().
+ */
+void devm_release_resource(struct device *dev, struct resource *new)
+{
+	WARN_ON(devres_release(dev, devm_resource_release, devm_resource_match,
+			       new));
+}
+EXPORT_SYMBOL(devm_release_resource);
+
 struct region_devres {
 	struct resource *parent;
 	resource_size_t start;
-- 
2.0.1