HID: alps: allow incoming reports when only the trackstick is opened

If userspace only reads the trackstick node, and no one is listening to
the touchpad nor the hidraw node then, the device is not powered on.

Add open/close callbacks to allow users to disable the touchpad in Gnome
while keeping the trackstick active.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1559632
Link: https://gitlab.gnome.org/GNOME/mutter/issues/128
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-alps.c

@@ -660,6 +660,20 @@ static int T4_init(struct hid_device *hdev, struct alps_dev *pri_data)
 	return ret;
 }
 
+static int alps_sp_open(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+
+	return hid_hw_open(hid);
+}
+
+static void alps_sp_close(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+
+	hid_hw_close(hid);
+}
+
 static int alps_input_configured(struct hid_device *hdev, struct hid_input *hi)
 {
 	struct alps_dev *data = hid_get_drvdata(hdev);
@@ -733,6 +747,10 @@ static int alps_input_configured(struct hid_device *hdev, struct hid_input *hi)
 		input2->id.version = input->id.version;
 		input2->dev.parent = input->dev.parent;
 
+		input_set_drvdata(input2, hdev);
+		input2->open = alps_sp_open;
+		input2->close = alps_sp_close;
+
 		__set_bit(EV_KEY, input2->evbit);
 		data->sp_btn_cnt = (data->sp_btn_info & 0x0F);
 		for (i = 0; i < data->sp_btn_cnt; i++)