From: Andre Noll <maan@systemlinux.org>
Date: Sun, 31 May 2009 10:34:39 +0000 (+0200)
Subject: alsa_write: Avoid EAGAIN.
X-Git-Tag: v0.3.5~42
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=e7b866a338a22ad07c8e60d405616a8065be89b1;p=paraslash.git

alsa_write: Avoid EAGAIN.

Before writing to the sound device, use snd_pcm_avail_update() to
check how many frames alsa will accept and write only that many
frames.
---

diff --git a/alsa_write.c b/alsa_write.c
index f01b8cf3..cf0f335b 100644
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -166,19 +166,19 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 {
 	struct private_alsa_write_data *pad = wn->private_data;
 	struct writer_node_group *wng = wn->wng;
-	size_t frames, bytes = *wng->loaded - wn->written;
+	size_t bytes = *wng->loaded - wn->written;
 	unsigned char *data = (unsigned char*)*wng->bufp + wn->written;
 	struct timeval tv;
-	snd_pcm_sframes_t ret;
+	snd_pcm_sframes_t ret, frames, avail;
 
 	if (*wng->input_error < 0 && (!pad->handle || bytes < pad->bytes_per_frame)) {
 		wn->written = *wng->loaded;
 		return *wng->input_error;
 	}
 	if (!bytes) /* no data available */
-		goto out;
+		return 0;
 	if (tv_diff(now, &pad->next_chunk, NULL) < 0)
-		goto out;
+		return 0;
 	if (!pad->handle) {
 		int err = alsa_init(pad, wn->conf);
 		if (err < 0)
@@ -186,30 +186,29 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 	}
 	frames = bytes / pad->bytes_per_frame;
 	if (!frames) /* less than a single frame available */
-		goto out;
+		return 0;
+	avail = snd_pcm_avail_update(pad->handle);
+	if (avail <= 0)
+		goto delay;
+	frames = PARA_MIN(frames, avail);
 	ret = snd_pcm_writei(pad->handle, data, frames);
-	if (ret == -EPIPE) {
-		PARA_WARNING_LOG("EPIPE\n");
-		snd_pcm_prepare(pad->handle);
-		return 1;
-	}
-	if (ret < 0 && ret != -EAGAIN) {
-		PARA_WARNING_LOG("alsa error (%zu frames, ret = %d\n",
-			frames, (int)ret);
+	if (ret < 0) {
+		PARA_WARNING_LOG("%s\n", snd_strerror(-ret));
+		if (ret == -EPIPE) {
+			snd_pcm_prepare(pad->handle);
+			return 0;
+		}
+		if (ret == -EAGAIN)
+			goto delay;
 		return -E_ALSA_WRITE;
 	}
-	if (ret == -EAGAIN)
-		PARA_DEBUG_LOG("EAGAIN\n");
-	else
-		wn->written += ret * pad->bytes_per_frame;
-	if (ret == frames) /* we wrote everything, try again immediately */
-		pad->next_chunk	= *now;
-	else { /* wait until 50% buffer space is available */
-		ms2tv(pad->buffer_time / 2000, &tv);
-		tv_add(now, &tv, &pad->next_chunk);
-	}
-out:
+	wn->written += ret * pad->bytes_per_frame;
 	return 1;
+delay:
+	/* wait until 50% buffer space is available */
+	ms2tv(pad->buffer_time / 2000, &tv);
+	tv_add(now, &tv, &pad->next_chunk);
+	return 0;
 }
 
 static void alsa_close(struct writer_node *wn)