usb: hook up device authorization to sysfs

Makes it possible to control the authorization of USB devices through
sysfs's /sys/usb/devices/*/authorize.

Update: per Adrian Bunk's suggestion, make dev_attr_authorized_default static
Signed-off-by: NInaky Perez-Gonzalez <inaky@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/sysfs.c

@@ -413,6 +413,44 @@ usb_descriptor_attr(bDeviceProtocol, "%02x\n")
 usb_descriptor_attr(bNumConfigurations, "%d\n")
 usb_descriptor_attr(bMaxPacketSize0, "%d\n")
 
+
+
+/* show if the device is authorized (1) or not (0) */
+static ssize_t usb_dev_authorized_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct usb_device *usb_dev = to_usb_device(dev);
+	return snprintf(buf, PAGE_SIZE, "%u\n", usb_dev->authorized);
+}
+
+
+/*
+ * Authorize a device to be used in the system
+ *
+ * Writing a 0 deauthorizes the device, writing a 1 authorizes it.
+ */
+static ssize_t usb_dev_authorized_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t size)
+{
+	ssize_t result;
+	struct usb_device *usb_dev = to_usb_device(dev);
+	unsigned val;
+	result = sscanf(buf, "%u\n", &val);
+	if (result != 1)
+		result = -EINVAL;
+	else if (val == 0)
+		result = usb_deauthorize_device(usb_dev);
+	else
+		result = usb_authorize_device(usb_dev);
+	return result < 0? result : size;
+}
+
+static DEVICE_ATTR(authorized, 0644,
+	    usb_dev_authorized_show, usb_dev_authorized_store);
+
+
 static struct attribute *dev_attrs[] = {
 	/* current configuration's attributes */
 	&dev_attr_configuration.attr,
@@ -435,6 +473,7 @@ static struct attribute *dev_attrs[] = {
 	&dev_attr_version.attr,
 	&dev_attr_maxchild.attr,
 	&dev_attr_quirks.attr,
+	&dev_attr_authorized.attr,
 	NULL,
 };
 static struct attribute_group dev_attr_grp = {