sound: pcm: record a substream's owner process

Record the pid of the task that opened a PCM substream. For sound
cards with hardware mixing, this allows determining which process
is associated with a specific substream's volume control.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index de6d981de5d6..c83a4a79f16b 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -348,6 +348,8 @@ struct snd_pcm_group {		/* keep linked substreams */
         int count;
 };
 
+struct pid;
+
 struct snd_pcm_substream {
         struct snd_pcm *pcm;
         struct snd_pcm_str *pstr;
@@ -379,6 +381,7 @@ struct snd_pcm_substream {
         atomic_t mmap_count;
         unsigned int f_flags;
         void (*pcm_release)(struct snd_pcm_substream *);
+        struct pid *pid;
 #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
         /* -- OSS things -- */
         struct snd_pcm_oss_substream oss;