[Bluetooth] Add address and channel attribute to RFCOMM TTY device

Export the remote device address and channel of RFCOMM TTY device
via sysfs attributes. This allows udev to create better naming rules
for configured RFCOMM devices.
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/rfcomm/tty.c

@@ -189,6 +189,23 @@ static struct device *rfcomm_get_device(struct rfcomm_dev *dev)
 	return conn ? &conn->dev : NULL;
 }
 
+static ssize_t show_address(struct device *tty_dev, struct device_attribute *attr, char *buf)
+{
+	struct rfcomm_dev *dev = dev_get_drvdata(tty_dev);
+	bdaddr_t bdaddr;
+	baswap(&bdaddr, &dev->dst);
+	return sprintf(buf, "%s\n", batostr(&bdaddr));
+}
+
+static ssize_t show_channel(struct device *tty_dev, struct device_attribute *attr, char *buf)
+{
+	struct rfcomm_dev *dev = dev_get_drvdata(tty_dev);
+	return sprintf(buf, "%d\n", dev->channel);
+}
+
+static DEVICE_ATTR(address, S_IRUGO, show_address, NULL);
+static DEVICE_ATTR(channel, S_IRUGO, show_channel, NULL);
+
 static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
 {
 	struct rfcomm_dev *dev;
@@ -281,6 +298,14 @@ static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
 		return err;
 	}
 
+	dev_set_drvdata(dev->tty_dev, dev);
+
+	if (device_create_file(dev->tty_dev, &dev_attr_address) < 0)
+		BT_ERR("Failed to create address attribute");
+
+	if (device_create_file(dev->tty_dev, &dev_attr_channel) < 0)
+		BT_ERR("Failed to create channel attribute");
+
 	return dev->id;
 }