Re: [Bluez-devel] Regarding a2recv

["Henryk Plötz" <henryk@ploetzli.ch>]

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Moin,

Am Thu, 5 May 2005 13:45:12 +0100 (BST) schrieb Mayank Batra:

> Did you try what I suggested you in my mail titled 'A
> small Query' ?

Ah no, but luckily Brad did. However, that wasn't the problem. The
problem was that a2recv didn't correctly fill out the transaction
label. When responding to a request one must use the same transaction
label that the other side used.

I don't fully understand the logic behind what init_request() in
a2recv.c does to the transaction_label, but it's most likely wrong.

I therefore introduced a function init_response() that takes the header
of the command that was received and creates a positive response header.
init_request() is then used nowhere anymore, so I #if 0'd it. I also
went through a hcidump of the (now working) stream setup phase and
compared it to the AVDTP spec. Most of it looks correct now, except for
Open Stream Response and Start Stream Response, which are too long (I'm
not sure what to do about that as the additional byte(s) are reserved in
the struct open_stream_rsp and struct start_stream_rsp for the case of
an error).

So now I made it to "Sent start stream confirm" but not further as the
audio dongle doesn't seem to start streaming. The last three packets I
see in an hcidump are

1115349894.700415 > ACL data: handle 41 flags 0x02 dlen 7
    L2CAP(d): cid 0x0040 len 3 [psm 25]
      AVDTP(s): Start cmd: transaction 5
        ACP SEID 1
1115349894.700472 < ACL data: handle 41 flags 0x02 dlen 8
    L2CAP(d): cid 0x0041 len 4 [psm 25]
      AVDTP(m): ver 1 ext cc 2 pt 7 seqn 0 time 1090519040 ssrc 40962
1115349894.709416 > HCI Event: Number of Completed Packets (0x13) plen 5
  0000: 01 29 00 01 00                                    .)...

(The second packet is actually an almost proper Start Stream Response 
that's only decoded wrong by hcidump. hcidump -R shows
1115349894.700472 < 0000: 02 29 20 08 00 04 00 41  00 52 07 00 00
which is correct, except for the two trailing zeros.)

After that things sit still for about 6 seconds and then I get

1115351711.667759 > HCI Event: Disconn Complete (0x05) plen 4
  0000: 00 28 00 08                                       .(..

I have attached a dump of the whole process (and the beginning of 
the reconnections that the dongle tries after the failure).

Anyways: I have committed the changed transaction_label handling to 
CVS, so please check that it doesn't break your already working 
devices.

-- 
Henryk Plötz
Grüße aus Berlin
~~~~~~~ Un-CDs, nein danke! http://www.heise.de/ct/cd-register/ ~~~~~~~
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