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isdn/gigaset: unclog bas_gigaset AT response pipe

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Recover from a lost HD_RECEIVEATDATA_ACK message by sending a
zero-length HD_READ_ATMESSAGE command when ev_layer sends "+++".

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tilman Schmidt 2010-09-30 13:35:31 +00:00 committed by David S. Miller
parent 60798c68be
commit 4cb5e42f61
1 changed files with 22 additions and 0 deletions
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22
drivers/isdn/gigaset/bas-gigaset.c
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@ -1896,6 +1896,28 @@ static int gigaset_write_cmd(struct cardstate *cs, struct cmdbuf_t *cb)
* The next command will reopen the AT channel automatically.
*/
if (cb->len == 3 && !memcmp(cb->buf, "+++", 3)) {
/* If an HD_RECEIVEATDATA_ACK message remains unhandled
* because of an error, the base never sends another one.
* The response channel is thus effectively blocked.
* Closing and reopening the AT channel does *not* clear
* this condition.
* As a stopgap measure, submit a zero-length AT read
* before closing the AT channel. This has the undocumented
* effect of triggering a new HD_RECEIVEATDATA_ACK message
* from the base if necessary.
* The subsequent AT channel close then discards any pending
* messages.
*/
spin_lock_irqsave(&cs->lock, flags);
if (!(cs->hw.bas->basstate & BS_ATRDPEND)) {
kfree(cs->hw.bas->rcvbuf);
cs->hw.bas->rcvbuf = NULL;
cs->hw.bas->rcvbuf_size = 0;
cs->hw.bas->retry_cmd_in = 0;
atread_submit(cs, 0);
}
spin_unlock_irqrestore(&cs->lock, flags);
rc = req_submit(cs->bcs, HD_CLOSE_ATCHANNEL, 0, BAS_TIMEOUT);
if (cb->wake_tasklet)
tasklet_schedule(cb->wake_tasklet);