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Subject[PATCH 23/24] Bluetooth: Refactor write_room() calculation
Date
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>
---
net/bluetooth/rfcomm/tty.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index af775f3..3f44195 100644
--- 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;
}
--
1.8.1.2


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