From 1d456811ce4643889c9d6ad581bfe7e1c6ddd08e Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Sun, 12 Jan 2014 09:22:29 -0300 Subject: [PATCH] upstream: [media] em28xx-audio: don't wait for lock in non-block mode Pulseaudio has the bad habit of stopping a streaming audio if a device, opened in non-block mode, waits. It is impossible to avoid em28xx to wait, as it will send commands via I2C, and other I2C operations may be happening (firmware transfers, Remote Controller polling, etc). Yet, as each em28xx subdriver locks em28xx-dev to protect the access to the hardware, it is possible to minimize the audio glitches by returning -EAGAIN to pulseaudio, if the lock is already taken by another subdriver. Reported-by: Antti Palosaari Tested-by: Antti Palosaari Signed-off-by: Mauro Carvalho Chehab --- drivers/media/usb/em28xx/em28xx-audio.c | 48 +++++++++++++++++++++++++++++---- 1 file changed, 43 insertions(+), 5 deletions(-) diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c index f6fcee3..f004680 100644 --- a/drivers/media/usb/em28xx/em28xx-audio.c +++ b/drivers/media/usb/em28xx/em28xx-audio.c @@ -258,6 +258,13 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream) runtime->hw = snd_em28xx_hw_capture; if ((dev->alt == 0 || dev->audio_ifnum) && dev->adev.users == 0) { + int nonblock = !!(substream->f_flags & O_NONBLOCK); + + if (nonblock) { + if (!mutex_trylock(&dev->lock)) + return -EAGAIN; + } else + mutex_lock(&dev->lock); if (dev->audio_ifnum) dev->alt = 1; else @@ -269,7 +276,6 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream) /* Sets volume, mute, etc */ dev->mute = 0; - mutex_lock(&dev->lock); ret = em28xx_audio_analog_set(dev); if (ret < 0) goto err; @@ -441,11 +447,19 @@ static int em28xx_vol_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *value) { struct em28xx *dev = snd_kcontrol_chip(kcontrol); + struct snd_pcm_substream *substream = dev->adev.capture_pcm_substream; u16 val = (0x1f - (value->value.integer.value[0] & 0x1f)) | (0x1f - (value->value.integer.value[1] & 0x1f)) << 8; + int nonblock = 0; int rc; - mutex_lock(&dev->lock); + if (substream) + nonblock = !!(substream->f_flags & O_NONBLOCK); + if (nonblock) { + if (!mutex_trylock(&dev->lock)) + return -EAGAIN; + } else + mutex_lock(&dev->lock); rc = em28xx_read_ac97(dev, kcontrol->private_value); if (rc < 0) goto err; @@ -470,9 +484,17 @@ static int em28xx_vol_get(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *value) { struct em28xx *dev = snd_kcontrol_chip(kcontrol); + struct snd_pcm_substream *substream = dev->adev.capture_pcm_substream; + int nonblock = 0; int val; - mutex_lock(&dev->lock); + if (substream) + nonblock = !!(substream->f_flags & O_NONBLOCK); + if (nonblock) { + if (!mutex_trylock(&dev->lock)) + return -EAGAIN; + } else + mutex_lock(&dev->lock); val = em28xx_read_ac97(dev, kcontrol->private_value); mutex_unlock(&dev->lock); if (val < 0) @@ -494,9 +516,17 @@ static int em28xx_vol_put_mute(struct snd_kcontrol *kcontrol, { struct em28xx *dev = snd_kcontrol_chip(kcontrol); u16 val = value->value.integer.value[0]; + struct snd_pcm_substream *substream = dev->adev.capture_pcm_substream; + int nonblock = 0; int rc; - mutex_lock(&dev->lock); + if (substream) + nonblock = !!(substream->f_flags & O_NONBLOCK); + if (nonblock) { + if (!mutex_trylock(&dev->lock)) + return -EAGAIN; + } else + mutex_lock(&dev->lock); rc = em28xx_read_ac97(dev, kcontrol->private_value); if (rc < 0) goto err; @@ -524,9 +554,17 @@ static int em28xx_vol_get_mute(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *value) { struct em28xx *dev = snd_kcontrol_chip(kcontrol); + struct snd_pcm_substream *substream = dev->adev.capture_pcm_substream; + int nonblock = 0; int val; - mutex_lock(&dev->lock); + if (substream) + nonblock = !!(substream->f_flags & O_NONBLOCK); + if (nonblock) { + if (!mutex_trylock(&dev->lock)) + return -EAGAIN; + } else + mutex_lock(&dev->lock); val = em28xx_read_ac97(dev, kcontrol->private_value); mutex_unlock(&dev->lock); if (val < 0) -- 2.7.4