usb: interface authorization: SysFS part of USB interface authorization

This introduces an attribute for each interface to
authorize (1) or deauthorize (0) it:
/sys/bus/usb/devices/INTERFACE/authorized

Signed-off-by: Stefan Koch <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/core/sysfs.c

···
 }
 static DEVICE_ATTR_RO(supports_autosuspend);
 
+/*
+ * interface_authorized_show - show authorization status of an USB interface
+ * 1 is authorized, 0 is deauthorized
+ */
+static ssize_t interface_authorized_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+
+	return sprintf(buf, "%u\n", intf->authorized);
+}
+
+/*
+ * interface_authorized_store - authorize or deauthorize an USB interface
+ */
+static ssize_t interface_authorized_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	bool val;
+
+	if (strtobool(buf, &val) != 0)
+		return -EINVAL;
+
+	if (val)
+		usb_authorize_interface(intf);
+	else
+		usb_deauthorize_interface(intf);
+
+	return count;
+}
+static struct device_attribute dev_attr_interface_authorized =
+		__ATTR(authorized, S_IRUGO | S_IWUSR,
+		interface_authorized_show, interface_authorized_store);
+
 static struct attribute *intf_attrs[] = {
 	&dev_attr_bInterfaceNumber.attr,
 	&dev_attr_bAlternateSetting.attr,
···
 	&dev_attr_bInterfaceProtocol.attr,
 	&dev_attr_modalias.attr,
 	&dev_attr_supports_autosuspend.attr,
+	&dev_attr_interface_authorized.attr,
 	NULL,
 };
 static struct attribute_group intf_attr_grp = {