ALSA: firewire-lib: obsolete ctx_data.tx.first_dbc with CIP_UNALIGHED_DBC flag

Recent firmware for Fireworks board module have a quirk to start
transmission of CIP with non-zero value for its data block counter.
In current implementation of ALSA firewire stack, the quirk is handled
by 'struct amdtp_stream.ctx_data.tx.first_dbc' with value 0x02. However,
the value comes from reverse engineering. It's better to handle this
quirk without the explicit value.

In a process to parse CIP header, the quirk of data block counter
affects decision of sequence index in sequence-multiplexed data channel;
i.e. MIDI conformant data channel. In Fireworks, the index is decided
by the number of data blocks from top of the same CIP, thus the value
of data block counter is useless.

This commit adds CIP_UNALIGHED_DBC flag and obsoletes the explicit
value for this quirk.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp-am824.c

@@ -315,12 +315,16 @@ static void read_midi_messages(struct amdtp_stream *s,
 			       __be32 *buffer, unsigned int frames)
 {
 	struct amdtp_am824 *p = s->protocol;
-	unsigned int f, port;
 	int len;
 	u8 *b;
+	int f;
 
 	for (f = 0; f < frames; f++) {
-		port = (8 - s->ctx_data.tx.first_dbc + s->data_block_counter + f) % 8;
+		unsigned int port = f;
+
+		if (!(s->flags & CIP_UNALIGHED_DBC))
+			port += s->data_block_counter;
+		port %= 8;
 		b = (u8 *)&buffer[p->midi_position];
 
 		len = b[0] - 0x80;

sound/firewire/amdtp-stream.c

@@ -584,8 +584,7 @@ static int check_cip_header(struct amdtp_stream *s, const __be32 *buf,
 	    s->data_block_counter != UINT_MAX)
 		*dbc = s->data_block_counter;
 
-	if (((s->flags & CIP_SKIP_DBC_ZERO_CHECK) &&
-	     *dbc == s->ctx_data.tx.first_dbc) ||
+	if ((*dbc == 0x00 && (s->flags & CIP_SKIP_DBC_ZERO_CHECK)) ||
 	    s->data_block_counter == UINT_MAX) {
 		lost = false;
 	} else if (!(s->flags & CIP_DBC_IS_END_EVENT)) {

sound/firewire/amdtp-stream.h

@@ -33,6 +33,8 @@
  * @CIP_HEADER_WITHOUT_EOH: Only for in-stream. CIP Header doesn't include
  *	valid EOH.
  * @CIP_NO_HEADERS: a lack of headers in packets
+ * @CIP_UNALIGHED_DBC: Only for in-stream. The value of dbc is not alighed to
+ *	the value of current SYT_INTERVAL; e.g. initial value is not zero.
  */
 enum cip_flags {
 	CIP_NONBLOCKING		= 0x00,
@@ -45,6 +47,7 @@ enum cip_flags {
 	CIP_JUMBO_PAYLOAD	= 0x40,
 	CIP_HEADER_WITHOUT_EOH	= 0x80,
 	CIP_NO_HEADER		= 0x100,
+	CIP_UNALIGHED_DBC	= 0x200,
 };
 
 /**
@@ -119,8 +122,6 @@ struct amdtp_stream {
 			// Fixed interval of dbc between previos/current
 			// packets.
 			unsigned int dbc_interval;
-			// Indicate the value of dbc field in a first packet.
-			unsigned int first_dbc;
 		} tx;
 		struct {
 			// To calculate CIP data blocks and tstamp.

sound/firewire/fireworks/fireworks_stream.c

@@ -146,7 +146,7 @@ int snd_efw_stream_init_duplex(struct snd_efw *efw)
 	    (efw->firmware_version == 0x5070000 ||
 	     efw->firmware_version == 0x5070300 ||
 	     efw->firmware_version == 0x5080000))
-		efw->tx_stream.ctx_data.tx.first_dbc = 0x02;
+		efw->tx_stream.flags |= CIP_UNALIGHED_DBC;
 	/* AudioFire9 always reports wrong dbs. */
 	if (efw->is_af9)
 		efw->tx_stream.flags |= CIP_WRONG_DBS;