Bluetooth: Refactor write_room() calculation

Compute the amount of space available for a single write()
within rfcomm_room(); clamp to 0 for negative values. Note
this patch does not change the result of the computation.

Report the amount of room returned in the debug printk.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Tested-By: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index af775f35c019f088e4467837e0887170e269e72c..3f44195c04ad8ec212d6734b3bbce3129018f62b 100644 (file)
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -348,11 +348,18 @@ static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
 }
 
 /* ---- Send buffer ---- */
-static inline unsigned int rfcomm_room(struct rfcomm_dlc *dlc)
+static inline unsigned int rfcomm_room(struct rfcomm_dev *dev)
 {
-       /* We can't let it be zero, because we don't get a callback
-          when tx_credits becomes nonzero, hence we'd never wake up */
-       return dlc->mtu * (dlc->tx_credits?:1);
+       struct rfcomm_dlc *dlc = dev->dlc;
+
+       /* The limit is bogus; the number of packets which can
+        * currently be sent by the krfcommd thread has no relevance
+        * to the number of packets which can be queued on the dlc's
+        * tx queue.
+        */
+       int limit = dlc->mtu * (dlc->tx_credits?:1);
+
+       return max(0, limit - atomic_read(&dev->wmem_alloc));
 }
 
 static void rfcomm_wfree(struct sk_buff *skb)
@@ -809,16 +816,12 @@ static int rfcomm_tty_write(struct tty_struct *tty, const unsigned char *buf, in
 static int rfcomm_tty_write_room(struct tty_struct *tty)
 {
        struct rfcomm_dev *dev = (struct rfcomm_dev *) tty->driver_data;
-       int room;
+       int room = 0;
 
-       BT_DBG("tty %p", tty);
-
-       if (!dev || !dev->dlc)
-               return 0;
+       if (dev && dev->dlc)
+               room = rfcomm_room(dev);
 
-       room = rfcomm_room(dev->dlc) - atomic_read(&dev->wmem_alloc);
-       if (room < 0)
-               room = 0;
+       BT_DBG("tty %p room %d", tty, room);
 
        return room;
 }