ACPI: Add acpi_resource_consumer() to find device that claims a resource

Add acpi_resource_consumer().  This takes a struct resource and searches
the ACPI namespace for a device whose current resource settings (_CRS)
includes the resource.  It returns the device if it exists, or NULL if no
device uses the resource.

If more than one device uses the resource (this may happen in the case of
bridges), acpi_resource_consumer() returns the first one found by
acpi_get_devices() in its modified depth-first walk of the namespace.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
index 56241eb341f4b..cb57962ef7c45 100644
--- a/drivers/acpi/resource.c
+++ b/drivers/acpi/resource.c
@@ -664,3 +664,60 @@ int acpi_dev_filter_resource_type(struct acpi_resource *ares,
 	return (type & types) ? 0 : 1;
 }
 EXPORT_SYMBOL_GPL(acpi_dev_filter_resource_type);
+
+static int acpi_dev_consumes_res(struct acpi_device *adev, struct resource *res)
+{
+	struct list_head resource_list;
+	struct resource_entry *rentry;
+	int ret, found = 0;
+
+	INIT_LIST_HEAD(&resource_list);
+	ret = acpi_dev_get_resources(adev, &resource_list, NULL, NULL);
+	if (ret < 0)
+		return 0;
+
+	list_for_each_entry(rentry, &resource_list, node) {
+		if (resource_contains(rentry->res, res)) {
+			found = 1;
+			break;
+		}
+
+	}
+
+	acpi_dev_free_resource_list(&resource_list);
+	return found;
+}
+
+static acpi_status acpi_res_consumer_cb(acpi_handle handle, u32 depth,
+					 void *context, void **ret)
+{
+	struct resource *res = context;
+	struct acpi_device **consumer = (struct acpi_device **) ret;
+	struct acpi_device *adev;
+
+	if (acpi_bus_get_device(handle, &adev))
+		return AE_OK;
+
+	if (acpi_dev_consumes_res(adev, res)) {
+		*consumer = adev;
+		return AE_CTRL_TERMINATE;
+	}
+
+	return AE_OK;
+}
+
+/**
+ * acpi_resource_consumer - Find the ACPI device that consumes @res.
+ * @res: Resource to search for.
+ *
+ * Search the current resource settings (_CRS) of every ACPI device node
+ * for @res.  If we find an ACPI device whose _CRS includes @res, return
+ * it.  Otherwise, return NULL.
+ */
+struct acpi_device *acpi_resource_consumer(struct resource *res)
+{
+	struct acpi_device *consumer = NULL;
+
+	acpi_get_devices(NULL, acpi_res_consumer_cb, res, (void **) &consumer);
+	return consumer;
+}