ALSA: control: Provide a helper to look for the preferred subdevice

Instead of open-coding the search over the control file loop, provide
a helper function for the preferred subdevice assigned to the current
process.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 24 insertions, 3 deletions

diff --git a/sound/core/control.c b/sound/core/control.c
index bb96a467e88d..cd246a0bcd55 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -50,7 +50,7 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
         unsigned long flags;
         struct snd_card *card;
         struct snd_ctl_file *ctl;
-        int err;
+        int i, err;
 
         err = nonseekable_open(inode, file);
         if (err < 0)
@@ -79,8 +79,8 @@ static int snd_ctl_open(struct inode *inode, struct file *file)
         init_waitqueue_head(&ctl->change_sleep);
         spin_lock_init(&ctl->read_lock);
         ctl->card = card;
-        ctl->prefer_pcm_subdevice = -1;
-        ctl->prefer_rawmidi_subdevice = -1;
+        for (i = 0; i < SND_CTL_SUBDEV_ITEMS; i++)
+                ctl->preferred_subdevice[i] = -1;
         ctl->pid = get_pid(task_pid(current));
         file->private_data = ctl;
         write_lock_irqsave(&card->ctl_files_rwlock, flags);
@@ -1607,6 +1607,27 @@ static int snd_ctl_fasync(int fd, struct file * file, int on)
         return fasync_helper(fd, file, on, &ctl->fasync);
 }
 
+/* return the preferred subdevice number if already assigned;
+ * otherwise return -1
+ */
+int snd_ctl_get_preferred_subdevice(struct snd_card *card, int type)
+{
+        struct snd_ctl_file *kctl;
+        int subdevice = -1;
+
+        read_lock(&card->ctl_files_rwlock);
+        list_for_each_entry(kctl, &card->ctl_files, list) {
+                if (kctl->pid == task_pid(current)) {
+                        subdevice = kctl->preferred_subdevice[type];
+                        if (subdevice != -1)
+                                break;
+                }
+        }
+        read_unlock(&card->ctl_files_rwlock);
+        return subdevice;
+}
+EXPORT_SYMBOL_GPL(snd_ctl_get_preferred_subdevice);
+
 /*
  * ioctl32 compat
  */