Rework transport protocol

Use a more simple tranport protocol for the realtime data. Use a piece
of shared memory and a socket where we use a 1byte read/write to trigger
remote actions. Also use a ringbuffer for events.

spa/include/spa/ringbuffer.h

@@ -29,6 +29,8 @@ typedef struct _SpaRingbuffer SpaRingbuffer;
 #define SPA_RINGBUFFER_URI             "http://spaplug.in/ns/ringbuffer"
 #define SPA_RINGBUFFER_PREFIX          SPA_RINGBUFFER_URI "#"
 
+#include <string.h>
+
 #include <spa/defs.h>
 #include <spa/barrier.h>
 
@@ -115,7 +117,7 @@ spa_ringbuffer_get_read_offset (SpaRingbuffer *rbuf,
  * Fill @areas with pointers to read from. The total amount of
  * bytes that can be read can be obtained by summing the areas len fields.
  */
-static inline void
+static inline size_t
 spa_ringbuffer_get_read_areas (SpaRingbuffer      *rbuf,
                                SpaRingbufferArea   areas[2])
 {
@@ -134,6 +136,22 @@ spa_ringbuffer_get_read_areas (SpaRingbuffer      *rbuf,
     areas[0].len = avail;
     areas[1].len = 0;
   }
+  return avail;
+}
+
+static inline void
+spa_ringbuffer_read_data (SpaRingbuffer      *rbuf,
+                          void               *buffer,
+                          SpaRingbufferArea   areas[2],
+                          void               *data,
+                          size_t              size)
+{
+  if (SPA_LIKELY (size < areas[0].len))
+    memcpy (data, buffer + areas[0].offset, size);
+  else {
+    memcpy (data, buffer + areas[0].offset, areas[0].len);
+    memcpy (data + areas[0].len, buffer, size - areas[0].len);
+  }
 }
 
 /**
@@ -173,7 +191,7 @@ spa_ringbuffer_get_write_offset (SpaRingbuffer *rbuf,
  * Fill @areas with pointers to write to. The total amount of
  * bytes that can be written can be obtained by summing the areas len fields.
  */
-static inline void
+static inline size_t
 spa_ringbuffer_get_write_areas (SpaRingbuffer      *rbuf,
                                 SpaRingbufferArea   areas[2])
 {
@@ -192,6 +210,22 @@ spa_ringbuffer_get_write_areas (SpaRingbuffer      *rbuf,
     areas[0].len = avail;
     areas[1].len = 0;
   }
+  return avail;
+}
+
+static inline void
+spa_ringbuffer_write_data (SpaRingbuffer      *rbuf,
+                           void               *buffer,
+                           SpaRingbufferArea   areas[2],
+                           void               *data,
+                           size_t              size)
+{
+  if (SPA_LIKELY (size < areas[0].len))
+    memcpy (buffer + areas[0].offset, data, size);
+  else {
+    memcpy (buffer + areas[0].offset, data, areas[0].len);
+    memcpy (buffer, data + areas[0].len, size - areas[0].len);
+  }
 }
 
 /**
@@ -210,6 +244,7 @@ spa_ringbuffer_write_advance (SpaRingbuffer      *rbuf,
   rbuf->writeindex = (rbuf->writeindex + len) & rbuf->mask2;
 }
 
+
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif

spa/plugins/alsa/alsa-source.c

@@ -698,7 +698,7 @@ spa_alsa_source_node_port_pull_output (SpaNode           *node,
 
     info[i].buffer_id = b->outbuf->id;
     info[i].status = SPA_RESULT_OK;
-    spa_log_debug (this->log, "pull buffer %u", b->outbuf->id);
+    spa_log_trace (this->log, "pull buffer %u", b->outbuf->id);
   }
   if (have_error)
     return SPA_RESULT_ERROR;
@@ -728,7 +728,7 @@ spa_alsa_source_node_port_reuse_buffer (SpaNode         *node,
   if (buffer_id >= this->n_buffers)
     return SPA_RESULT_INVALID_BUFFER_ID;
 
-  spa_log_debug (this->log, "recycle buffer %u", buffer_id);
+  spa_log_trace (this->log, "recycle buffer %u", buffer_id);
   recycle_buffer (this, buffer_id);
 
   return SPA_RESULT_OK;

spa/plugins/alsa/alsa-utils.c

@@ -221,14 +221,20 @@ set_swparams (SpaALSAState *state)
 
   CHECK (snd_pcm_sw_params_set_silence_threshold (hndl, params, 0U), "set_silence_threshold");
 
+#if 1
   /* allow the transfer when at least period_size samples can be processed */
   /* or disable this mechanism when period event is enabled (aka interrupt like style processing) */
   CHECK (snd_pcm_sw_params_set_avail_min (hndl, params,
         props->period_event ? state->buffer_frames : state->period_frames), "set_avail_min");
+
   /* enable period events when requested */
   if (props->period_event) {
     CHECK (snd_pcm_sw_params_set_period_event (hndl, params, 1), "set_period_event");
   }
+#else
+  CHECK (snd_pcm_sw_params_set_avail_min (hndl, params, 0), "set_avail_min");
+#endif
+
   /* write the parameters to the playback device */
   CHECK (snd_pcm_sw_params (hndl, params), "sw_params");
 
@@ -328,8 +334,7 @@ pull_frames_ringbuffer (SpaALSAState *state,
   src = SPA_MEMBER (b->outbuf->datas[0].data, b->outbuf->datas[0].offset, void);
   dst = SPA_MEMBER (my_areas[0].addr, offset * state->frame_size, uint8_t);
 
-  spa_ringbuffer_get_read_areas (&b->rb->ringbuffer, areas);
-  avail = areas[0].len + areas[1].len;
+  avail = spa_ringbuffer_get_read_areas (&b->rb->ringbuffer, areas);
   size = SPA_MIN (avail, frames * state->frame_size);
 
   spa_log_debug (state->log, "%zd %zd %zd %zd %zd %zd",
@@ -337,13 +342,11 @@ pull_frames_ringbuffer (SpaALSAState *state,
       areas[1].offset, areas[1].len, offset, size);
 
   if (size > 0) {
-    areas[0].len = SPA_MIN (areas[0].len, size);
-    areas[1].len = SPA_MIN (areas[1].len, size - areas[0].len);
-
-    memcpy (dst, src + areas[0].offset, areas[0].len);
-    if (areas[1].len)
-      memcpy (dst + areas[0].len, src + areas[1].offset, areas[1].len);
-
+    spa_ringbuffer_read_data (&b->rb->ringbuffer,
+                              src,
+                              areas,
+                              dst,
+                              size);
     spa_ringbuffer_read_advance (&b->rb->ringbuffer, size);
     frames = size / state->frame_size;
   } else {
@@ -371,6 +374,7 @@ mmap_write (SpaALSAState *state)
   snd_pcm_status_t *status;
   SpaNodeEventNeedInput ni;
 
+#if 0
   snd_pcm_status_alloca (&status);
 
   if ((err = snd_pcm_status (hndl, status)) < 0) {
@@ -379,6 +383,12 @@ mmap_write (SpaALSAState *state)
   }
 
   avail = snd_pcm_status_get_avail (status);
+#else
+  if ((avail = snd_pcm_avail_update (hndl)) < 0) {
+    spa_log_error (state->log, "snd_pcm_avail_update error: %s", snd_strerror (avail));
+    return -1;
+  }
+#endif
 
   ni.event.type = SPA_NODE_EVENT_TYPE_NEED_INPUT;
   ni.event.size = sizeof (ni);
@@ -403,7 +413,6 @@ mmap_write (SpaALSAState *state)
       if (err != -EPIPE && err != -ESTRPIPE)
         return -1;
     }
-    spa_log_debug (state->log, "write %zd/%zd/%zd %u", frames, size, avail, state->ready.length);
     size -= frames;
   }
   return 0;
@@ -552,6 +561,7 @@ spa_alsa_start (SpaALSAState *state, bool xrun_recover)
     spa_log_error (state->log, "Invalid poll descriptors count %d", state->poll.n_fds);
     return SPA_RESULT_ERROR;
   }
+
   if ((err = snd_pcm_poll_descriptors (state->hndl, (struct pollfd *)state->fds, state->poll.n_fds)) < 0) {
     spa_log_error (state->log, "snd_pcm_poll_descriptors: %s", snd_strerror(err));
     return SPA_RESULT_ERROR;