ACPI: Make acpi_dev_get_resources() method agnostic

The function acpi_dev_get_resources() is completely generic and
can be used to parse resource objects that are not necessarily
coming from the _CRS method but also from other objects eg _DMA
that have the same _CRS resource format.

Create an acpi_dev_get_resources() helper, internal to the ACPI
resources parsing compilation unit, __acpi_dev_get_resources(),
that takes a const char* parameter to detect which ACPI method should be
called to retrieve the resources list and make acpi_dev_get_resources()
call it with a method name _CRS leaving the API behaviour unchanged.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/resource.c

@@ -573,6 +573,35 @@ static acpi_status acpi_dev_process_resource(struct acpi_resource *ares,
 	return AE_OK;
 }
 
+static int __acpi_dev_get_resources(struct acpi_device *adev,
+				    struct list_head *list,
+				    int (*preproc)(struct acpi_resource *, void *),
+				    void *preproc_data, char *method)
+{
+	struct res_proc_context c;
+	acpi_status status;
+
+	if (!adev || !adev->handle || !list_empty(list))
+		return -EINVAL;
+
+	if (!acpi_has_method(adev->handle, method))
+		return 0;
+
+	c.list = list;
+	c.preproc = preproc;
+	c.preproc_data = preproc_data;
+	c.count = 0;
+	c.error = 0;
+	status = acpi_walk_resources(adev->handle, method,
+				     acpi_dev_process_resource, &c);
+	if (ACPI_FAILURE(status)) {
+		acpi_dev_free_resource_list(list);
+		return c.error ? c.error : -EIO;
+	}
+
+	return c.count;
+}
+
 /**
  * acpi_dev_get_resources - Get current resources of a device.
  * @adev: ACPI device node to get the resources for.
@@ -601,28 +630,8 @@ int acpi_dev_get_resources(struct acpi_device *adev, struct list_head *list,
 			   int (*preproc)(struct acpi_resource *, void *),
 			   void *preproc_data)
 {
-	struct res_proc_context c;
-	acpi_status status;
-
-	if (!adev || !adev->handle || !list_empty(list))
-		return -EINVAL;
-
-	if (!acpi_has_method(adev->handle, METHOD_NAME__CRS))
-		return 0;
-
-	c.list = list;
-	c.preproc = preproc;
-	c.preproc_data = preproc_data;
-	c.count = 0;
-	c.error = 0;
-	status = acpi_walk_resources(adev->handle, METHOD_NAME__CRS,
-				     acpi_dev_process_resource, &c);
-	if (ACPI_FAILURE(status)) {
-		acpi_dev_free_resource_list(list);
-		return c.error ? c.error : -EIO;
-	}
-
-	return c.count;
+	return __acpi_dev_get_resources(adev, list, preproc, preproc_data,
+					METHOD_NAME__CRS);
 }
 EXPORT_SYMBOL_GPL(acpi_dev_get_resources);