usb: Add support for indicating whether a port is removable

Userspace may want to make policy decisions based on whether or not a
given USB device is removable. Add a per-device member and support
for exposing it in sysfs. Information sources to populate it will be
added later.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-usb

@@ -182,3 +182,14 @@ Description:
 		USB2 hardware LPM is enabled for the device. Developer can
 		write y/Y/1 or n/N/0 to the file to enable/disable the
 		feature.
+
+What:		/sys/bus/usb/devices/.../removable
+Date:		February 2012
+Contact:	Matthew Garrett <mjg@redhat.com>
+Description:
+		Some information about whether a given USB device is
+		physically fixed to the platform can be inferred from a
+		combination of hub decriptor bits and platform-specific data
+		such as ACPI. This file will read either "removable" or
+		"fixed" if the information is available, and "unknown"
+		otherwise.

drivers/usb/core/sysfs.c

@@ -230,6 +230,28 @@ show_urbnum(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(urbnum, S_IRUGO, show_urbnum, NULL);
 
+static ssize_t
+show_removable(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_device *udev;
+	char *state;
+
+	udev = to_usb_device(dev);
+
+	switch (udev->removable) {
+	case USB_DEVICE_REMOVABLE:
+		state = "removable";
+		break;
+	case USB_DEVICE_FIXED:
+		state = "fixed";
+		break;
+	default:
+		state = "unknown";
+	}
+
+	return sprintf(buf, "%s\n", state);
+}
+static DEVICE_ATTR(removable, S_IRUGO, show_removable, NULL);
 
 #ifdef	CONFIG_PM
 
@@ -626,6 +648,7 @@ static struct attribute *dev_attrs[] = {
 	&dev_attr_avoid_reset_quirk.attr,
 	&dev_attr_authorized.attr,
 	&dev_attr_remove.attr,
+	&dev_attr_removable.attr,
 	NULL,
 };
 static struct attribute_group dev_attr_grp = {

include/linux/usb.h

@@ -376,6 +376,12 @@ struct usb_bus {
 
 struct usb_tt;
 
+enum usb_device_removable {
+	USB_DEVICE_REMOVABLE_UNKNOWN = 0,
+	USB_DEVICE_REMOVABLE,
+	USB_DEVICE_FIXED,
+};
+
 /**
  * struct usb_device - kernel's representation of a USB device
  * @devnum: device number; address on a USB bus
@@ -432,6 +438,7 @@ struct usb_tt;
  * @wusb_dev: if this is a Wireless USB device, link to the WUSB
  *	specific data for the device.
  * @slot_id: Slot ID assigned by xHCI
+ * @removable: Device can be physically removed from this port
  *
  * Notes:
  * Usbcore drivers should not set usbdev->state directly.  Instead use
@@ -509,6 +516,7 @@ struct usb_device {
 #endif
 	struct wusb_dev *wusb_dev;
 	int slot_id;
+	enum usb_device_removable removable;
 };
 #define	to_usb_device(d) container_of(d, struct usb_device, dev)