[PATCH 1/3] ALSA: control: Introduce snd_ctl_find_id_mixer_locked()

[Richard Fitzgerald <rf@opensource.cirrus.com>]

Adds wrapper function snd_ctl_find_id_mixer_locked(). This is
identical to snd_ctl_find_id_mixer() except that it can be called
from code that is already holding controls_rwsem.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 include/sound/control.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/sound/control.h b/include/sound/control.h
index 9a4f4f7138da..c1659036c4a7 100644
--- a/include/sound/control.h
+++ b/include/sound/control.h
@@ -167,6 +167,29 @@ snd_ctl_find_id_mixer(struct snd_card *card, const char *name)
 	return snd_ctl_find_id(card, &id);
 }
 
+/**
+ * snd_ctl_find_id_mixer_locked - find the control instance with the given name string
+ * @card: the card instance
+ * @name: the name string
+ *
+ * Finds the control instance with the given name and
+ * @SNDRV_CTL_ELEM_IFACE_MIXER. Other fields are set to zero.
+ *
+ * This is merely a wrapper to snd_ctl_find_id_locked().
+ * The caller must down card->controls_rwsem before calling this function.
+ *
+ * Return: The pointer of the instance if found, or %NULL if not.
+ */
+static inline struct snd_kcontrol *
+snd_ctl_find_id_mixer_locked(struct snd_card *card, const char *name)
+{
+	struct snd_ctl_elem_id id = {};
+
+	id.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
+	strscpy(id.name, name, sizeof(id.name));
+	return snd_ctl_find_id_locked(card, &id);
+}
+
 int snd_ctl_create(struct snd_card *card);
 
 int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn);
-- 
2.39.2