[PATCH v2 5/6] sound/usb: pcm changes to use media token api

From: Shuah Khan
Date: Tue Oct 14 2014 - 10:59:37 EST

Change snd_usb_capture_ops trigger to hold audio token prior
starting endpoints for SNDRV_PCM_TRIGGER_START request and
release after stopping endpoints for SNDRV_PCM_TRIGGER_STOP
request. Audio token is released from snd_usb_capture_ops
close interface to cover the case where an application exits
without stopping capture. Audio token get request will succeed
if it is free or when a media application with the same task
pid or task gid makes the request. This covers the cases when
a media application first hold the tuner nd audio token and
then requests SNDRV_PCM_TRIGGER_START either from the same
thread or a another thread in the same process group.

Signed-off-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
sound/usb/pcm.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index c62a165..d23abeb 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -21,6 +21,7 @@
#include <linux/usb.h>
#include <linux/usb/audio.h>
#include <linux/usb/audio-v2.h>
+#include <linux/media_tknres.h>

#include <sound/core.h>
#include <sound/pcm.h>
@@ -1220,6 +1221,7 @@ static int snd_usb_pcm_close(struct snd_pcm_substream *substream, int direction)

subs->pcm_substream = NULL;
+ media_put_audio_tkn(&subs->dev->dev);

return 0;
@@ -1573,6 +1575,12 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream

switch (cmd) {
+ err = media_get_audio_tkn(&subs->dev->dev);
+ if (err == -EBUSY) {
+ dev_info(&subs->dev->dev, "%s device is busy\n",
+ __func__);
+ return err;
+ }
err = start_endpoints(subs, false);
if (err < 0)
return err;
@@ -1583,6 +1591,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
stop_endpoints(subs, false);
subs->running = 0;
+ media_put_audio_tkn(&subs->dev->dev);
return 0;
subs->data_endpoint->retire_data_urb = NULL;

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