ALSA: virtio: handling control and I/O messages for the PCM device

The driver implements a message-based transport for I/O substream
operations. Before the start of the substream, the hardware buffer is
sliced into I/O messages, the number of which is equal to the current
number of periods. The size of each message is equal to the current
size of one period.

I/O messages are organized in an ordered queue. The completion of the
I/O message indicates an elapsed period (the only exception is the end
of the stream for the capture substream). Upon completion, the message
is automatically re-added to the end of the queue.

Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Link: https://lore.kernel.org/r/20210302164709.3142702-6-anton.yakovlev@opensynergy.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 32 insertions, 0 deletions

diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c
index e16567e2e214..2dcd763efa29 100644
--- a/sound/virtio/virtio_pcm.c
+++ b/sound/virtio/virtio_pcm.c
@@ -353,6 +353,8 @@ int virtsnd_pcm_parse_cfg(struct virtio_snd *snd)
 		vss->snd = snd;
 		vss->sid = i;
 		INIT_WORK(&vss->elapsed_period, virtsnd_pcm_period_elapsed);
+		init_waitqueue_head(&vss->msg_empty);
+		spin_lock_init(&vss->lock);
 
 		rc = virtsnd_pcm_build_hw(vss, &info[i]);
 		if (rc)
@@ -477,3 +479,33 @@ int virtsnd_pcm_build_devs(struct virtio_snd *snd)
 
 	return 0;
 }
+
+/**
+ * virtsnd_pcm_event() - Handle the PCM device event notification.
+ * @snd: VirtIO sound device.
+ * @event: VirtIO sound event.
+ *
+ * Context: Interrupt context.
+ */
+void virtsnd_pcm_event(struct virtio_snd *snd, struct virtio_snd_event *event)
+{
+	struct virtio_pcm_substream *vss;
+	u32 sid = le32_to_cpu(event->data);
+
+	if (sid >= snd->nsubstreams)
+		return;
+
+	vss = &snd->substreams[sid];
+
+	switch (le32_to_cpu(event->hdr.code)) {
+	case VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED:
+		/* TODO: deal with shmem elapsed period */
+		break;
+	case VIRTIO_SND_EVT_PCM_XRUN:
+		spin_lock(&vss->lock);
+		if (vss->xfer_enabled)
+			vss->xfer_xrun = true;
+		spin_unlock(&vss->lock);
+		break;
+	}
+}