6835822 some OSS applications have unacceptably large audio latency

5 files changed, 96 insertions, 14 deletions

diff --git a/usr/src/uts/common/io/audio/impl/audio_client.c b/usr/src/uts/common/io/audio/impl/audio_client.c
index f3514df49b..8ed13f1d41 100644
--- a/usr/src/uts/common/io/audio/impl/audio_client.c
+++ b/usr/src/uts/common/io/audio/impl/audio_client.c
@@ -129,6 +129,15 @@ auclnt_get_nframes(audio_stream_t *sp)
 	return (sp->s_nframes);
 }
 
+void
+auclnt_set_latency(audio_stream_t *sp, unsigned frags, unsigned bytes)
+{
+	mutex_enter(&sp->s_lock);
+	sp->s_hintfrags = (uint16_t)frags;
+	sp->s_hintsz = bytes;
+	mutex_exit(&sp->s_lock);
+}
+
 uint64_t
 auclnt_get_head(audio_stream_t *sp)
 {
diff --git a/usr/src/uts/common/io/audio/impl/audio_client.h b/usr/src/uts/common/io/audio/impl/audio_client.h
index d38b1485a8..197a14bdff 100644
--- a/usr/src/uts/common/io/audio/impl/audio_client.h
+++ b/usr/src/uts/common/io/audio/impl/audio_client.h
@@ -102,6 +102,8 @@ uint64_t auclnt_get_tail(audio_stream_t *);
 unsigned auclnt_get_hidx(audio_stream_t *);
 unsigned auclnt_get_tidx(audio_stream_t *);
 
+void auclnt_set_latency(audio_stream_t *, unsigned, unsigned);
+
 audio_stream_t *auclnt_input_stream(audio_client_t *);
 audio_stream_t *auclnt_output_stream(audio_client_t *);
 
diff --git a/usr/src/uts/common/io/audio/impl/audio_format.c b/usr/src/uts/common/io/audio/impl/audio_format.c
index b7385e336c..81a5f80c4d 100644
--- a/usr/src/uts/common/io/audio/impl/audio_format.c
+++ b/usr/src/uts/common/io/audio/impl/audio_format.c
@@ -839,7 +839,36 @@ auimpl_format_setup(audio_stream_t *sp, audio_parms_t *uparms)
 	sp->s_framesz = info->sampsize * uparms->p_nchan;
 	sp->s_fragfr = (uparms->p_rate / sp->s_engine->e_intrs);
 	sp->s_fragbytes = sp->s_fragfr * sp->s_framesz;
-	sp->s_nfrags = sp->s_allocsz / sp->s_fragbytes;
+
+	/*
+	 * We need to "tune" the buffer and fragment counts for some
+	 * uses...  OSS applications may like to configure a low
+	 * latency, and they rely upon write() to block to prevent too
+	 * much data from being queued up.
+	 */
+	if (sp->s_hintsz) {
+		sp->s_nfrags = sp->s_hintsz / sp->s_fragbytes;
+	} else if (sp->s_hintfrags) {
+		sp->s_nfrags = sp->s_hintfrags;
+	} else {
+		sp->s_nfrags = sp->s_allocsz / sp->s_fragbytes;
+	}
+
+	/*
+	 * Now make sure that the hint works -- we need at least 2 fragments,
+	 * and we need to fit within the room allocated to us.
+	 */
+	if (sp->s_nfrags < 2) {
+		sp->s_nfrags = 2;
+	}
+	while ((sp->s_nfrags * sp->s_fragbytes) > sp->s_allocsz) {
+		sp->s_nfrags--;
+	}
+	/* if the resulting configuration is invalid, note it */
+	if (sp->s_nfrags < 2) {
+		return (EINVAL);
+	}
+
 	sp->s_nframes = sp->s_nfrags * sp->s_fragfr;
 	sp->s_nbytes = sp->s_nframes * sp->s_framesz;
 	*sp->s_user_parms = *uparms;
diff --git a/usr/src/uts/common/io/audio/impl/audio_impl.h b/usr/src/uts/common/io/audio/impl/audio_impl.h
index 7c8099ea88..562ad3eb9a 100644
--- a/usr/src/uts/common/io/audio/impl/audio_impl.h
+++ b/usr/src/uts/common/io/audio/impl/audio_impl.h
@@ -84,7 +84,9 @@ struct audio_stream {
 #define	s_tidx			s_buf.b_tidx
 #define	s_hidx			s_buf.b_hidx
 	ddi_umem_cookie_t	s_cookie;
-	size_t			s_allocsz;
+	uint32_t		s_allocsz;
+	uint32_t		s_hintsz;	/* latency hints */
+	uint16_t		s_hintfrags;
 
 	/*
 	 * Various counters.
diff --git a/usr/src/uts/common/io/audio/impl/audio_oss.c b/usr/src/uts/common/io/audio/impl/audio_oss.c
index cbd08cc407..37ff03fbc7 100644
--- a/usr/src/uts/common/io/audio/impl/audio_oss.c
+++ b/usr/src/uts/common/io/audio/impl/audio_oss.c
@@ -508,6 +508,8 @@ oss_open(audio_client_t *c, int oflag)
 		    ((rv = auclnt_set_channels(osp, OSS_CHANNELS)) != 0)) {
 			goto failed;
 		}
+		/* default to 5 fragments to provide reasonable latency */
+		auclnt_set_latency(osp, 5, 0);
 	}
 
 	if (oflag & FREAD) {
@@ -516,6 +518,8 @@ oss_open(audio_client_t *c, int oflag)
 		    ((rv = auclnt_set_channels(isp, OSS_CHANNELS)) != 0)) {
 			goto failed;
 		}
+		/* default to 5 fragments to provide reasonable latency */
+		auclnt_set_latency(isp, 5, 0);
 	}
 
 	return (0);
@@ -1032,17 +1036,40 @@ sndctl_dsp_sync(audio_client_t *c)
 static int
 sndctl_dsp_setfragment(audio_client_t *c, int *fragp)
 {
-	_NOTE(ARGUNUSED(c));
-	_NOTE(ARGUNUSED(fragp));
+	int	bufsz;
+	int	nfrags;
+	int	fragsz;
+
+	nfrags = (*fragp) >> 16;
+	if ((nfrags >= 0x7fffU) || (nfrags < 2)) {
+		/* use infinite setting... no change */
+		return (0);
+	}
+
+	fragsz = (*fragp) & 0xffff;
+	if (fragsz > 16) {
+		/* basically too big, so, no change */
+		return (0);
+	}
+	bufsz = (1U << fragsz) * nfrags;
+
+	/*
+	 * Now we have our desired buffer size, but we have to
+	 * make sure we have a whole number of fragments >= 2, and
+	 * less than the maximum.
+	 */
+	bufsz = ((*fragp) >> 16) * (1U << (*fragp));
+	if (bufsz >= 65536) {
+		return (0);
+	}
+
+	/*
+	 * We set the latency hints in terms of bytes, not fragments.
+	 */
+	auclnt_set_latency(auclnt_output_stream(c), 0, bufsz);
+	auclnt_set_latency(auclnt_input_stream(c), 0, bufsz);
+
 	/*
-	 * We don't really implement this "properly" at this time.
-	 * The problems with this ioctl are various: the API insists
-	 * that fragment sizes be a power of two -- and we can't cope
-	 * with accurately reporting fragment sizes in the face of
-	 * mixing and format conversion.
-	 *
-	 * Well behaved applications should really not use this API.
-	 *
 	 * According to the OSS API documentation, the values provided
 	 * are nothing more than a "hint" and not to be relied upon
 	 * anyway.  And we aren't obligated to report the actual
@@ -1051,6 +1078,17 @@ sndctl_dsp_setfragment(audio_client_t *c, int *fragp)
 	return (0);
 }
 
+static int
+sndctl_dsp_policy(audio_client_t *c, int *policy)
+{
+	int	hint = *policy;
+	if ((hint >= 2) && (hint <= 10)) {
+		auclnt_set_latency(auclnt_input_stream(c), hint, 0);
+		auclnt_set_latency(auclnt_output_stream(c), hint, 0);
+	}
+	return (0);
+}
+
 /*
  * A word about recsrc, and playtgt ioctls: We don't allow ordinary DSP
  * applications to change port configurations, because these could have a
@@ -1723,7 +1761,6 @@ oss_ioctl(audio_client_t *c, int cmd, intptr_t arg, int mode, cred_t *credp,
 	case SNDCTL_DSP_GET_RECSRC_NAMES:
 		rv = sndctl_dsp_get_recsrc_names(c, (oss_mixer_enuminfo *)data);
 		break;
-	case SNDCTL_DSP_SUBDIVIDE:
 	case SNDCTL_DSP_SETFRAGMENT:
 		rv = sndctl_dsp_setfragment(c, (int *)data);
 		break;
@@ -1757,12 +1794,15 @@ oss_ioctl(audio_client_t *c, int cmd, intptr_t arg, int mode, cred_t *credp,
 	case SNDCTL_DSP_SETRECVOL:
 		rv = sndctl_dsp_setrecvol(c, (int *)data);
 		break;
+	case SNDCTL_DSP_SUBDIVIDE:	/* Ignored */
 	case SNDCTL_DSP_SETDUPLEX:	/* Ignored */
 	case SNDCTL_DSP_LOW_WATER:	/* Ignored */
-	case SNDCTL_DSP_POLICY:		/* Ignored */
 	case SNDCTL_DSP_PROFILE:	/* Ignored */
 		rv = 0;
 		break;
+	case SNDCTL_DSP_POLICY:
+		rv = sndctl_dsp_policy(c, (int *)data);
+		break;
 	case SNDCTL_DSP_GETBLKSIZE:
 		rv = sndctl_dsp_getblksize(c, (int *)data);
 		break;