Re: [FFADO-devel] [PATCH 42/44] bebob/firewire-lib: Add a quirk of wrong dbc in empty packet for M-Audio special Firewire series

[Euan de Kock <euan@dekock.net>]

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Thanks for the update. This bit me last night, and I just commented out the check to keep working.

I'll try and retest it tonight with this version. (On a Echo Audiofire Pre8 with firmware  < 5)

Regards,

Euan deKock.

On 23 March 2014 10:16:58 AM AWST, Takashi Sakamoto <o-takashi@sakamocchi.jp> wrote:
>I realize this patch includes a bug to cause wrong detection of packet 
>discontinuity.
>
>> @@ -745,6 +745,8 @@ static void handle_in_packet(struct amdtp_stream
>*s,
>>
>>   	/* Check data block counter continuity */
>>   	data_block_counter = cip_header[0] & AMDTP_DBC_MASK;
>> +	if (data_blocks == 0 && (s->flags & CIP_EMPTY_HAS_WRONG_DBC))
>> +		data_block_counter = s->data_block_counter;
>>   	if (!(s->flags & CIP_DBC_IS_END_EVENT)) {
>>   		lost = data_block_counter != s->data_block_counter;
>>   	} else {
>
>These lines should be:
>
> > +	if (data_blocks == 0 && (s->flags & CIP_EMPTY_HAS_WRONG_DBC) &&
> > +         s->data_block_counter != UINT_MAX)
> > +		data_block_counter = s->data_block_counter;
>
>
>When CIP_SKIP_INIT_DBC_CHECK is enabled, initial value of 
>s->data_block_counter is set to UINT_MAX. An intention of this is to 
>skip detecting discontinuity for a first packet [31/44].
>
>This initial value has a bad effect when CIP_EMPTY_HAS_WRONG_DBC is
>enabled.
>
>A first packet is an empty packet. When this packet is handled, 
>data_block_counter is set to initial value of s->data_block_counter 
>(UINT_MAX). Later, s->data_block_counter is set to 0xff with bitmask in
>
>below lines.
>
>         if (s->flags & CIP_DBC_IS_END_EVENT)
>                 s->data_block_counter = data_block_counter;
>         else
>                 s->data_block_counter =
>                             (data_block_counter + data_blocks) & 0xff;
>
>When a packet with data blocks is handled later, s->data_block_counter 
>is 0xff, not UINT_MAX. This causes discontinuity detection because this
>
>packet has 0x00 in itx dbc in below lines.
>
>         if (lost && s->data_block_counter != UINT_MAX) {
>                 dev_info(&s->unit->device,
>                          "Detect discontinuity of CIP: %02X %02X\n",
>                          s->data_block_counter, data_block_counter);
>
>See this log:
>[ 2933.102892] 01020000 9002FFFF 02
>[ 2933.102894] 01020000 9002FFFF 02
>[ 2933.102896] 01020000 9002FFFF 02
>[ 2933.102899] 01020000 9002FFFF 02
>[ 2933.102901] 01020000 9002FFFF 02
>[ 2933.102903] 01020000 9002FFFF 02
>[ 2933.104871] 01110000 900258B5 8A
>[ 2933.104877] snd-bebob fw1.0: Detect discontinuity of CIP: FF 00
>
>I'm sorry to post a patch including a bug.
>
>
>Regards
>
>Takashi Sakamoto
>o-takashi@sakamocchi.jp
>
>
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------------------------------------------------------------------------------
Learn Graph Databases - Download FREE O'Reilly Book
"Graph Databases" is the definitive new guide to graph databases and their
applications. Written by three acclaimed leaders in the field,
this first edition is now available. Download your free book today!
http://p.sf.net/sfu/13534_NeoTech

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