Commit 7fde4d77 authored by Matthias Goebl's avatar Matthias Goebl Committed by David S. Miller

[ISDN]: i4l: Fix DLE handling for i4l-audio

The DLE handling in i4l-audio seems to be broken.

It produces spurious DLEs so asterisk 1.2.24 with chan_modem_i4l
gets irritated, the error message is:
"chan_modem_i4l.c:450 i4l_read: Value of escape is ^ (17)".
-> There shouldn't be a DLE-^.
If a spurious DLE-ETX occurs, the audio connection even dies.
I use a "AVM Fritz!PCI" isdn card.

I found two issues that only appear if ISDN_AUDIO_SKB_DLECOUNT(skb) > 0:
- The loop in isdn_tty.c:isdn_tty_try_read() doesn't escape a DLE if it's
  the last character.

- The loop in isdn_common.c:isdn_readbchan_tty() doesn't copy its characters,
  it only remembers the last one ("last = *p;").

  Compare it with the loop in isdn_common.c:isdn_readbchan(), that *does*
  copy them ("*cp++ = *p;") correctly.
  The special handling of the "last" character made it more difficult.
  I compared it to linux-2.4.19: There was no "last"-handling and both loops
  did escape and copy all characters correctly.
Signed-off-by: default avatarMatthias Goebl <>
Signed-off-by: default avatarDavid S. Miller <>
parent 00409bb0
......@@ -914,6 +914,9 @@ isdn_readbchan_tty(int di, int channel, struct tty_struct *tty, int cisco_hack)
dflag = 0;
count_pull = count_put = 0;
while ((count_pull < skb->len) && (len > 0)) {
/* push every character but the last to the tty buffer directly */
if ( count_put )
tty_insert_flip_char(tty, last, TTY_NORMAL);
if (dev->drv[di]->DLEflag & DLEmask) {
last = DLE;
......@@ -85,6 +85,8 @@ isdn_tty_try_read(modem_info * info, struct sk_buff *skb)
tty_insert_flip_char(tty, DLE, 0);
tty_insert_flip_char(tty, *dp++, 0);
if (*dp == DLE)
tty_insert_flip_char(tty, DLE, 0);
last = *dp;
} else {
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment