ACPI: utils: Introduce helper for _DEP list lookup

The ACPI LPSS driver and the Surface platform driver code use almost the
same code pattern for checking if one ACPI device is present in the list
returned by _DEP for another ACPI device.

To reduce the resulting code duplication, introduce a helper for that
called acpi_device_dep() and invoke it from both places.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 57663065dbf6..abac5cc25477 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -450,6 +450,40 @@ void acpi_handle_list_free(struct acpi_handle_list *list)
 }
 EXPORT_SYMBOL_GPL(acpi_handle_list_free);
 
+/**
+ * acpi_device_dep - Check ACPI device dependency
+ * @target: ACPI handle of the target ACPI device.
+ * @match: ACPI handle to look up in the target's _DEP list.
+ *
+ * Return true if @match is present in the list returned by _DEP for
+ * @target or false otherwise.
+ */
+bool acpi_device_dep(acpi_handle target, acpi_handle match)
+{
+	struct acpi_handle_list dep_devices;
+	bool ret = false;
+	int i;
+
+	if (!acpi_has_method(target, "_DEP"))
+		return false;
+
+	if (!acpi_evaluate_reference(target, "_DEP", NULL, &dep_devices)) {
+		acpi_handle_debug(target, "Failed to evaluate _DEP.\n");
+		return false;
+	}
+
+	for (i = 0; i < dep_devices.count; i++) {
+		if (dep_devices.handles[i] == match) {
+			ret = true;
+			break;
+		}
+	}
+
+	acpi_handle_list_free(&dep_devices);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(acpi_device_dep);
+
 acpi_status
 acpi_get_physical_device_location(acpi_handle handle, struct acpi_pld_info **pld)
 {