Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 475c9079bf85..f2f9873bb5c3 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -29,6 +29,7 @@
 #include <linux/dynamic_debug.h>
 
 #include "internal.h"
+#include "sleep.h"
 
 #define _COMPONENT		ACPI_BUS_COMPONENT
 ACPI_MODULE_NAME("utils");
@@ -709,6 +710,36 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, int rev, u64 funcs)
 }
 EXPORT_SYMBOL(acpi_check_dsm);
 
+/**
+ * acpi_dev_present - Detect presence of a given ACPI device in the system.
+ * @hid: Hardware ID of the device.
+ *
+ * Return %true if the device was present at the moment of invocation.
+ * Note that if the device is pluggable, it may since have disappeared.
+ *
+ * For this function to work, acpi_bus_scan() must have been executed
+ * which happens in the subsys_initcall() subsection. Hence, do not
+ * call from a subsys_initcall() or earlier (use acpi_get_devices()
+ * instead). Calling from module_init() is fine (which is synonymous
+ * with device_initcall()).
+ */
+bool acpi_dev_present(const char *hid)
+{
+	struct acpi_device_bus_id *acpi_device_bus_id;
+	bool found = false;
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry(acpi_device_bus_id, &acpi_bus_id_list, node)
+		if (!strcmp(acpi_device_bus_id->bus_id, hid)) {
+			found = true;
+			break;
+		}
+	mutex_unlock(&acpi_device_lock);
+
+	return found;
+}
+EXPORT_SYMBOL(acpi_dev_present);
+
 /*
  * acpi_backlight= handling, this is done here rather then in video_detect.c
  * because __setup cannot be used in modules.