Takashi Sakamoto wrote:
Generally, the devices can synchronize to handle 'presentation timestamp' in CIP packets. This commit adds functionality to pick up this timestamp from in-packets transmitted by the device, then use it for out packets.
In current implementation, this module generated the timestamp by itself. This is 'SYT Match' mode. Then this drive acts as synchronization master. This commit allows this module to act as synchronization slave.
This commit restricts this mechanism is only available in blocking mode because handling the timestamp in non-blocking mode is more complicated than in blocking mode.
+++ b/sound/firewire/amdtp.c @@ -72,6 +73,10 @@ int amdtp_stream_init(struct amdtp_stream *s, struct fw_unit *unit,
- s->sync_slave = ERR_PTR(-1);
This pointer does not report any actual error code either.
@@ -626,7 +631,7 @@ static void handle_out_packet(struct amdtp_stream *s, unsigned int syt) {
- struct snd_pcm_substream *pcm;
- struct snd_pcm_substream *pcm = NULL;
Why this change in this patch?
@@ -768,6 +773,15 @@ static void in_stream_callback(struct fw_iso_context *context, u32 cycle,
/* Process sync slave stream */if ((s->flags & CIP_BLOCKING) &&(s->flags & CIP_SYNC_TO_DEVICE) &&s->sync_slave->callbacked) {
It might be easier to check just s->sync_slave instead of multiple flags.
- /* when sync to device, flush the packets for slave stream */
- if ((s->flags & CIP_BLOCKING) &&
(s->flags & CIP_SYNC_TO_DEVICE) && s->sync_slave->callbacked)
Same here.
+/* this is executed one time */ +static void amdtp_stream_callback(struct fw_iso_context *context, u32 cycle,
This name is rather generic; this is not "the" callback, but the "initial" or "first" callback.
...
- return;
+}
This is not necessary here.
+static inline void amdtp_stream_set_sync(enum cip_flags sync_mode,
struct amdtp_stream *master,struct amdtp_stream *slave)+{
- /* clear sync flag */
- master->flags &= ~CIP_SYNC_TO_DEVICE;
- slave->flags &= ~CIP_SYNC_TO_DEVICE;
This needs to be done only if sync_mode != CIP_SYNC_TO_DEVICE.
Regards, Clemens