ALSA: firewire-lib: fix to process MIDI conformant data channel for AM824 format

In IEC 61883-6, 8 MIDI data streams are multiplexed into single MIDI
conformant data channel. The index of stream is calculated by modulo 8
of the value of data block counter. Therefore data block processing
layer requires valid value of data block counter.

In recent changes of ALSA IEC 61883-1/6 engine, the value of data block
counter is changed before calling data block processing layer. This
brings miss detection of MIDI messages in non-blocking transmission
method is used.

This commit fixes the bug by changing chached data block counter after
calling data block processing layer.

Fixes: e335425b6596 ("ALSA: firewire-lib: split helper function to check incoming CIP header")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index b341bd86605e63be50fbc805b89b79cabe538add..91b8902418400f886afcd6a7bf797cb6f765af99 100644 (file)
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -614,11 +614,10 @@ static int check_cip_header(struct amdtp_stream *s, const __be32 *buf,
 static int parse_ir_ctx_header(struct amdtp_stream *s, unsigned int cycle,
                               const __be32 *ctx_header,
                               unsigned int *payload_length,
-                              unsigned int *data_blocks,
+                              unsigned int *data_blocks, unsigned int *dbc,
                               unsigned int *syt, unsigned int index)
 {
        const __be32 *cip_header;
-       unsigned int dbc;
        int err;
 
        *payload_length = be32_to_cpu(ctx_header[0]) >> ISO_DATA_LENGTH_SHIFT;
@@ -633,32 +632,28 @@ static int parse_ir_ctx_header(struct amdtp_stream *s, unsigned int cycle,
        if (!(s->flags & CIP_NO_HEADER)) {
                cip_header = ctx_header + 2;
                err = check_cip_header(s, cip_header, *payload_length,
-                                      data_blocks, &dbc, syt);
+                                      data_blocks, dbc, syt);
                if (err < 0) {
                        if (err != -EAGAIN)
                                return err;
 
                        *data_blocks = 0;
-                       dbc = s->data_block_counter;
                }
        } else {
                cip_header = NULL;
                err = 0;
                *data_blocks = *payload_length / sizeof(__be32) /
                               s->data_block_quadlets;
-               dbc = s->data_block_counter;
+               *dbc = s->data_block_counter;
                *syt = 0;
        }
 
        if (err >= 0 && s->flags & CIP_DBC_IS_END_EVENT)
-               s->data_block_counter = dbc;
+               s->data_block_counter = *dbc;
 
        trace_amdtp_packet(s, cycle, cip_header, *payload_length, *data_blocks,
                           index);
 
-       if (err >= 0 && !(s->flags & CIP_DBC_IS_END_EVENT))
-               s->data_block_counter = (dbc + *data_blocks) & 0xff;
-
        return err;
 }
 
@@ -761,7 +756,8 @@ static void in_stream_callback(struct fw_iso_context *context, u32 tstamp,
        for (i = 0; i < packets; i++) {
                u32 cycle;
                unsigned int payload_length;
-               unsigned int data_block;
+               unsigned int data_blocks;
+               unsigned int dbc;
                unsigned int syt;
                __be32 *buffer;
                unsigned int pcm_frames = 0;
@@ -771,13 +767,19 @@ static void in_stream_callback(struct fw_iso_context *context, u32 tstamp,
 
                cycle = compute_cycle_count(ctx_header[1]);
                err = parse_ir_ctx_header(s, cycle, ctx_header, &payload_length,
-                                         &data_block, &syt, i);
+                                         &data_blocks, &dbc, &syt, i);
                if (err < 0 && err != -EAGAIN)
                        break;
+
                if (err >= 0) {
                        buffer = s->buffer.packets[s->packet_index].buffer;
                        pcm_frames = s->process_data_blocks(s, buffer,
-                                                           data_block, &syt);
+                                                           data_blocks, &syt);
+
+                       if (!(s->flags & CIP_DBC_IS_END_EVENT)) {
+                               s->data_block_counter =
+                                               (dbc + data_blocks) & 0xff;
+                       }
                }
 
                if (queue_in_packet(s, &params) < 0)