2 files changed, 53 insertions, 2 deletions

diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 9195deba9d94..ebb593e9c380 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -113,6 +113,9 @@ static const struct file_operations acpi_button_state_fops = {
         .release = single_release,
 };
 
+static BLOCKING_NOTIFIER_HEAD(acpi_lid_notifier);
+static struct acpi_device *lid_device;
+
 /* --------------------------------------------------------------------------
                               FS Interface (/proc)
    -------------------------------------------------------------------------- */
@@ -229,11 +232,38 @@ static int acpi_button_remove_fs(struct acpi_device *device)
 /* --------------------------------------------------------------------------
                                 Driver Interface
    -------------------------------------------------------------------------- */
+int acpi_lid_notifier_register(struct notifier_block *nb)
+{
+        return blocking_notifier_chain_register(&acpi_lid_notifier, nb);
+}
+EXPORT_SYMBOL(acpi_lid_notifier_register);
+
+int acpi_lid_notifier_unregister(struct notifier_block *nb)
+{
+        return blocking_notifier_chain_unregister(&acpi_lid_notifier, nb);
+}
+EXPORT_SYMBOL(acpi_lid_notifier_unregister);
+
+int acpi_lid_open(void)
+{
+        acpi_status status;
+        unsigned long long state;
+
+        status = acpi_evaluate_integer(lid_device->handle, "_LID", NULL,
+                                       &state);
+        if (ACPI_FAILURE(status))
+                return -ENODEV;
+
+        return !!state;
+}
+EXPORT_SYMBOL(acpi_lid_open);
+
 static int acpi_lid_send_state(struct acpi_device *device)
 {
         struct acpi_button *button = acpi_driver_data(device);
         unsigned long long state;
         acpi_status status;
+        int ret;
 
         status = acpi_evaluate_integer(device->handle, "_LID", NULL, &state);
         if (ACPI_FAILURE(status))
@@ -242,7 +272,12 @@ static int acpi_lid_send_state(struct acpi_device *device)
         /* input layer checks if event is redundant */
         input_report_switch(button->input, SW_LID, !state);
         input_sync(button->input);
-        return 0;
+
+        ret = blocking_notifier_call_chain(&acpi_lid_notifier, state, device);
+        if (ret == NOTIFY_DONE)
+                ret = blocking_notifier_call_chain(&acpi_lid_notifier, state,
+                                                   device);
+        return ret;
 }
 
 static void acpi_button_notify(struct acpi_device *device, u32 event)
@@ -364,8 +399,14 @@ static int acpi_button_add(struct acpi_device *device)
         error = input_register_device(input);
         if (error)
                 goto err_remove_fs;
-        if (button->type == ACPI_BUTTON_TYPE_LID)
+        if (button->type == ACPI_BUTTON_TYPE_LID) {
                 acpi_lid_send_state(device);
+                /*
+                 * This assumes there's only one lid device, or if there are
+                 * more we only care about the last one...
+                 */
+                lid_device = device;
+        }
 
         if (device->wakeup.flags.valid) {
                 /* Button's GPE is run-wake GPE */
diff --git a/include/acpi/button.h b/include/acpi/button.h
new file mode 100644
index 000000000000..bb643a79d651
--- /dev/null
+++ b/include/acpi/button.h
@@ -0,0 +1,10 @@
+#ifndef ACPI_BUTTON_H
+#define ACPI_BUTTON_H
+
+#include <linux/notifier.h>
+
+extern int acpi_lid_notifier_register(struct notifier_block *nb);
+extern int acpi_lid_notifier_unregister(struct notifier_block *nb);
+extern int acpi_lid_open(void);
+
+#endif /* ACPI_BUTTON_H */