[PATCH v2 1/4] ALSA: vmaster: Add snd_ctl_add_followers() helper

[Takashi Iwai <tiwai@suse.de>]

Add a new helper to add multiple vmaster followers in a shot.  The
same function was open-coded in various places, and this helper
replaces them.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/control.h |  3 +++
 sound/core/vmaster.c    | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/sound/control.h b/include/sound/control.h
index 69d950a34ca3..9a4f4f7138da 100644
--- a/include/sound/control.h
+++ b/include/sound/control.h
@@ -262,6 +262,9 @@ snd_ctl_add_follower(struct snd_kcontrol *master, struct snd_kcontrol *follower)
 	return _snd_ctl_add_follower(master, follower, 0);
 }
 
+int snd_ctl_add_followers(struct snd_card *card, struct snd_kcontrol *master,
+			  const char * const *list);
+
 /**
  * snd_ctl_add_follower_uncached - Add a virtual follower control
  * @master: vmaster element
diff --git a/sound/core/vmaster.c b/sound/core/vmaster.c
index d0f11f37889b..378d2c7c3d4a 100644
--- a/sound/core/vmaster.c
+++ b/sound/core/vmaster.c
@@ -280,6 +280,34 @@ int _snd_ctl_add_follower(struct snd_kcontrol *master,
 }
 EXPORT_SYMBOL(_snd_ctl_add_follower);
 
+/**
+ * snd_ctl_add_followers - add multiple followers to vmaster
+ * @card: card instance
+ * @master: the target vmaster kcontrol object
+ * @list: NULL-terminated list of name strings of followers to be added
+ *
+ * Adds the multiple follower kcontrols with the given names.
+ * Returns 0 for success or a negative error code.
+ */
+int snd_ctl_add_followers(struct snd_card *card, struct snd_kcontrol *master,
+			  const char * const *list)
+{
+	struct snd_kcontrol *follower;
+	int err;
+
+	for (; *list; list++) {
+		follower = snd_ctl_find_id_mixer(card, *list);
+		if (follower) {
+			err = snd_ctl_add_follower(master, follower);
+			if (err < 0)
+				return err;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_ctl_add_followers);
+
 /*
  * ctl callbacks for master controls
  */
-- 
2.35.3