Fix issues with ALSA OSS backend for firefox and chrome.

1) When read() or write() fails due to EAGAIN because no buffer is available or
   buffer is full, return 0 instead of failure. Else clients may simply close
   the device and re-open it instantly chopping the audio.
2) Implement OSS delay function to fix an issue with negative delays.
3) Use at least 16ms of HW buffer by default to avoid jitter.

Approved by:	pi, jbeich

1 files changed, 126 insertions, 3 deletions

diff --git a/audio/alsa-plugins/files/patch-oss_pcm__oss.c b/audio/alsa-plugins/files/patch-oss_pcm__oss.c
index 79966ae29fb8..ab9d39d01951 100644
--- a/audio/alsa-plugins/files/patch-oss_pcm__oss.c
+++ b/audio/alsa-plugins/files/patch-oss_pcm__oss.c
@@ -1,4 +1,4 @@
---- oss/pcm_oss.c.orig	2016-07-26 13:27:23 UTC
+--- oss/pcm_oss.c.orig	2019-07-04 14:37:07 UTC
 +++ oss/pcm_oss.c
 @@ -22,7 +22,11 @@
  #include <sys/ioctl.h>
@@ -12,7 +12,55 @@
  
  #define ARRAY_SIZE(x)	(sizeof(x) / sizeof(*(x)))
  
-@@ -258,7 +262,7 @@ static int oss_drain(snd_pcm_ioplug_t *i
+@@ -74,11 +78,19 @@ static snd_pcm_sframes_t oss_write(snd_p
+ 	size *= oss->frame_bytes;
+ 	result = write(oss->fd, buf, size);
+ #ifdef __FreeBSD__
+-	if (result == -1)
+-		return -errno;
++	if (result == -1) {
++		if (errno == EAGAIN)
++			return 0;
++		else
++			return -errno;
++	}
+ #else
+-	if (result <= 0)
+-		return result;
++	if (result <= 0) {
++		if (result == -EAGAIN)
++			return 0;
++		else
++			return result;
++	}
+ #endif
+ 	return result / oss->frame_bytes;
+ }
+@@ -97,11 +109,19 @@ static snd_pcm_sframes_t oss_read(snd_pc
+ 	size *= oss->frame_bytes;
+ 	result = read(oss->fd, buf, size);
+ #ifdef __FreeBSD__
+-	if (result == -1)
+-		return -errno;
++	if (result == -1) {
++		if (errno == EAGAIN)
++			return 0;
++		else
++			return -errno;
++	}
+ #else
+-	if (result <= 0)
+-		return result;
++	if (result <= 0) {
++		if (result == -EAGAIN)
++			return 0;
++		else
++			return result;
++	}
+ #endif
+ 	return result / oss->frame_bytes;
+ }
+@@ -258,10 +278,29 @@ static int oss_drain(snd_pcm_ioplug_t *i
  #endif
  
  	if (io->stream == SND_PCM_STREAM_PLAYBACK)
@@ -21,7 +69,29 @@
  	return 0;
  }
  
-@@ -272,7 +276,7 @@ static int oss_prepare(snd_pcm_ioplug_t 
++static int oss_delay(snd_pcm_ioplug_t *io, snd_pcm_sframes_t *delayp)
++{
++	snd_pcm_oss_t *oss = io->private_data;
++	int tmp;
++
++	if (oss->fd < 0)
++		return -EBADFD;
++
++	if (io->stream == SND_PCM_STREAM_PLAYBACK) {
++		if (ioctl(oss->fd, SNDCTL_DSP_GETODELAY, &tmp) < 0 || tmp < 0)
++			tmp = 0;
++	} else {
++		tmp = 0;
++	}
++	*delayp = snd_pcm_bytes_to_frames(io->pcm, tmp);
++
++	return (0);
++}
++
+ #ifndef __FreeBSD__
+ static int oss_prepare(snd_pcm_ioplug_t *io)
+ {
+@@ -272,7 +311,7 @@ static int oss_prepare(snd_pcm_ioplug_t 
  	fprintf(stderr, "%s()\n", __func__);
  #endif
  
@@ -30,3 +100,56 @@
  
  	tmp = io->channels;
  	if (ioctl(oss->fd, SNDCTL_DSP_CHANNELS, &tmp) < 0) {
+@@ -380,20 +419,26 @@ static int oss_hw_params(snd_pcm_ioplug_
+ 
+ 	ioctl(oss->fd, SNDCTL_DSP_RESET);
+ 
+-#define blksz_aligned()		((1 << blksz_shift) -			\
+-				((1 << blksz_shift) % oss->frame_bytes))
+-	blksz_shift = 16;
+-	tmp = io->period_size * oss->frame_bytes;
++	/* use a 16ms HW buffer by default */
++	tmp = ((16 * io->rate) / 1000) * oss->frame_bytes;
+ 
+-	while (blksz_shift > 4 && blksz_aligned() > tmp)
+-		blksz_shift--;
++	/* round up to nearest power of two */
++	while (tmp & (tmp - 1))
++		tmp += tmp & ~(tmp - 1);
++
++	/* get logarithmic value */
++	for (blksz_shift = 0; blksz_shift < 24; blksz_shift++) {
++		if (tmp == (1 << blksz_shift))
++			break;
++	}
+ 
+-	blkcnt = 2;
+ 	tmp = io->buffer_size * oss->frame_bytes;
+ 
+-	while (blkcnt < 4096 && (blksz_aligned() * blkcnt) < tmp &&
+-	    ((1 << blksz_shift) * blkcnt) < 131072)
+-		blkcnt <<= 1;
++	/* compute HW buffer big enough to hold SW buffer */
++	for (blkcnt = FREEBSD_OSS_BLKCNT_MIN; blkcnt != FREEBSD_OSS_BLKCNT_MAX; blkcnt *= 2) {
++		if ((blkcnt << blksz_shift) >= tmp)
++			break;
++	}
+ 
+ 	tmp = blksz_shift | (blkcnt << 16);
+ 	if (ioctl(oss->fd, SNDCTL_DSP_SETFRAGMENT, &tmp) < 0) {
+@@ -767,6 +812,7 @@ static const snd_pcm_ioplug_callback_t o
+ 	.prepare = oss_prepare,
+ #endif
+ 	.drain = oss_drain,
++	.delay = oss_delay,
+ };
+ 
+ static const snd_pcm_ioplug_callback_t oss_capture_callback = {
+@@ -780,6 +826,7 @@ static const snd_pcm_ioplug_callback_t o
+ 	.prepare = oss_prepare,
+ #endif
+ 	.drain = oss_drain,
++	.delay = oss_delay,
+ };
+ 
+