ALSA: firewire-lib: flush completed packets when reading PCM position

By flushing all completed but not yet reported packets before reading
the PCM hardware position, the granularity of the pointer is improved
from the interrupt interval to the packet size.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/firewire/amdtp.c

@@ -531,6 +531,20 @@ err_unlock:
 }
 EXPORT_SYMBOL(amdtp_out_stream_start);
 
+/**
+ * amdtp_out_stream_pcm_pointer - get the PCM buffer position
+ * @s: the AMDTP output stream that transports the PCM data
+ *
+ * Returns the current buffer position, in frames.
+ */
+unsigned long amdtp_out_stream_pcm_pointer(struct amdtp_out_stream *s)
+{
+	fw_iso_context_flush_completions(s->context);
+
+	return ACCESS_ONCE(s->pcm_buffer_pointer);
+}
+EXPORT_SYMBOL(amdtp_out_stream_pcm_pointer);
+
 /**
  * amdtp_out_stream_update - update the stream after a bus reset
  * @s: the AMDTP output stream