resources: Add device-managed request/release_resource()

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>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Tejun Heo <tj@kernel.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index da14b8d09296..ca24f19f9d18 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1248,6 +1248,76 @@ 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) {
+                dev_err(dev, "resource collision: %pR conflicts with %s %pR\n",
+                        new, conflict->name, conflict);
+                devres_free(ptr);
+                return -EBUSY;
+        }
+
+        devres_add(dev, ptr);
+        return 0;
+}
+EXPORT_SYMBOL(devm_request_resource);
+
+static int devm_resource_match(struct device *dev, void *res, void *data)
+{
+        struct resource **ptr = res;
+
+        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;