ALSA: PCM: User contol API implementation

Introduced a new helper function snd_pcm_add_usr_ctls() to
create control elements representing the user control for each
PCM (sub)stream

Signed-off-by: Jayasena Sangaraboina <jsanga@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>

include/sound/pcm.h

@@ -519,6 +519,7 @@ struct snd_pcm_str {
 #endif
 	struct snd_kcontrol *chmap_kctl; /* channel-mapping controls */
 	struct snd_kcontrol *vol_kctl; /* volume controls */
+	struct snd_kcontrol *usr_kctl; /* user controls */
 	struct device dev;
 };
 
@@ -1435,6 +1436,30 @@ int snd_pcm_add_volume_ctls(struct snd_pcm *pcm, int stream,
 			   unsigned long private_value,
 			   struct snd_pcm_volume **info_ret);
 
+/*
+ * PCM User control API
+ */
+/* array element of usr elem */
+struct snd_pcm_usr_elem {
+	int val[128];
+};
+
+/* pp information; retrieved via snd_kcontrol_chip() */
+struct snd_pcm_usr {
+	struct snd_pcm *pcm;	/* assigned PCM instance */
+	int stream;		/* PLAYBACK or CAPTURE */
+	struct snd_kcontrol *kctl;
+	const struct snd_pcm_usr_elem *usr;
+	int max_length;
+	void *private_data;	/* optional: private data pointer */
+};
+
+int snd_pcm_add_usr_ctls(struct snd_pcm *pcm, int stream,
+			 const struct snd_pcm_usr_elem *usr,
+			 int max_length, int max_control_str_len,
+			 unsigned long private_value,
+			 struct snd_pcm_usr **info_ret);
+
 /* printk helpers */
 #define pcm_err(pcm, fmt, args...) \
 	dev_err((pcm)->card->dev, fmt, ##args)

sound/core/pcm.c

@@ -1143,6 +1143,10 @@ static int snd_pcm_dev_disconnect(struct snd_device *device)
 			snd_ctl_remove(pcm->card, pcm->streams[cidx].vol_kctl);
 			pcm->streams[cidx].vol_kctl = NULL;
 		}
+		if (pcm->streams[cidx].usr_kctl) {
+			snd_ctl_remove(pcm->card, pcm->streams[cidx].usr_kctl);
+			pcm->streams[cidx].usr_kctl = NULL;
+		}
 	}
 	mutex_unlock(&pcm->open_mutex);
 	mutex_unlock(&register_mutex);

sound/core/pcm_lib.c

@@ -42,6 +42,7 @@
 #endif
 
 #define STRING_LENGTH_OF_INT 12
+#define MAX_USR_CTRL_CNT 128
 
 /*
  * fill ring buffer with silence
@@ -2728,3 +2729,95 @@ int snd_pcm_add_volume_ctls(struct snd_pcm *pcm, int stream,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(snd_pcm_add_volume_ctls);
+
+static int pcm_usr_ctl_info(struct snd_kcontrol *kcontrol,
+			    struct snd_ctl_elem_info *uinfo)
+{
+	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
+	uinfo->count = MAX_USR_CTRL_CNT;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = INT_MAX;
+	return 0;
+}
+
+static void pcm_usr_ctl_private_free(struct snd_kcontrol *kcontrol)
+{
+	struct snd_pcm_usr *info = snd_kcontrol_chip(kcontrol);
+	info->pcm->streams[info->stream].usr_kctl = NULL;
+	kfree(info);
+}
+
+/**
+ * snd_pcm_add_usr_ctls - create user control elements
+ * @pcm: the assigned PCM instance
+ * @stream: stream direction
+ * @max_length: the max length of the user parameter of stream
+ * @private_value: the value passed to each kcontrol's private_value field
+ * @info_ret: store struct snd_pcm_usr instance if non-NULL
+ *
+ * Create usr control elements assigned to the given PCM stream(s).
+ * Returns zero if succeed, or a negative error value.
+ */
+int snd_pcm_add_usr_ctls(struct snd_pcm *pcm, int stream,
+			 const struct snd_pcm_usr_elem *usr,
+			 int max_length, int max_kctrl_str_len,
+			 unsigned long private_value,
+			 struct snd_pcm_usr **info_ret)
+{
+	struct snd_pcm_usr *info;
+	struct snd_kcontrol_new knew = {
+		.iface = SNDRV_CTL_ELEM_IFACE_MIXER,
+		.access = SNDRV_CTL_ELEM_ACCESS_READWRITE,
+		.info = pcm_usr_ctl_info,
+	};
+	int err;
+	char *buf;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		pr_err("%s: snd_pcm_usr alloc failed\n", __func__);
+		return -ENOMEM;
+	}
+	info->pcm = pcm;
+	info->stream = stream;
+	info->usr = usr;
+	info->max_length = max_length;
+	buf = kzalloc(max_kctrl_str_len, GFP_KERNEL);
+	if (!buf) {
+		pr_err("%s: buffer allocation failed\n", __func__);
+		kfree(info);
+		return -ENOMEM;
+	}
+	knew.name = buf;
+	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
+		snprintf(buf, max_kctrl_str_len, "%s %d %s",
+			"Playback", pcm->device, "User kcontrol");
+	else
+		snprintf(buf, max_kctrl_str_len, "%s %d %s",
+			"Capture", pcm->device, "User kcontrol");
+	knew.device = pcm->device;
+	knew.count = pcm->streams[stream].substream_count;
+	knew.private_value = private_value;
+	info->kctl = snd_ctl_new1(&knew, info);
+	if (!info->kctl) {
+		kfree(info);
+		kfree(knew.name);
+		pr_err("%s: snd_ctl_new failed\n", __func__);
+		return -ENOMEM;
+	}
+	info->kctl->private_free = pcm_usr_ctl_private_free;
+	err = snd_ctl_add(pcm->card, info->kctl);
+	if (err < 0) {
+		kfree(info);
+		kfree(knew.name);
+		pr_err("%s: snd_ctl_add failed:%d\n", __func__,
+			err);
+		return -ENOMEM;
+	}
+	pcm->streams[stream].usr_kctl = info->kctl;
+	if (info_ret)
+		*info_ret = info;
+	kfree(knew.name);
+	return 0;
+}
+EXPORT_SYMBOL(snd_pcm_add_usr_ctls);