1 files changed, 319 insertions, 0 deletions
diff --git a/examples/plugins/sample_mixer_plugin.c b/examples/plugins/sample_mixer_plugin.c
new file mode 100644
index 0000000..e1a7567
--- /dev/null
+++ b/examples/plugins/sample_mixer_plugin.c
@@ -0,0 +1,319 @@
+/*
+** Copyright (c) 2021, The Linux Foundation. All rights reserved.
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above
+**     copyright notice, this list of conditions and the following
+**     disclaimer in the documentation and/or other materials provided
+**     with the distribution.
+**   * Neither the name of The Linux Foundation nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
+** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
+** ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
+** BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+** CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+** SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+** BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+** OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+** IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+**/
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sound/asound.h>
+#include <tinyalsa/plugin.h>
+#include <tinyalsa/asoundlib.h>
+
+#define SAMPLE_MIXER_PRIV_GET_CTL_PTR(p, idx) (p->ctls + idx)
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+
+static const char *const sample_enum_text[] = {"One", "Two", "Three"};
+
+struct sample_mixer_priv {
+    struct snd_control *ctls;
+    int ctl_count;
+
+    struct snd_value_enum sample_enum;
+
+    mixer_event_callback event_cb;
+};
+
+static int sample_mixer_int_ctl_get(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+    return 0;
+}
+
+static int sample_mixer_int_ctl_put(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+/*
+ *   Integer values can be retrieved using:
+ *   uint32_t val1 = (uint32_t)ev->value.integer.value[0];
+ *   uint32_t val2 = (uint32_t)ev->value.integer.value[1];
+ *   uint32_t val3 = (uint32_t)ev->value.integer.value[2];
+ */
+    return 0;
+}
+
+static int sample_mixer_byte_array_ctl_get(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+    return 0;
+}
+
+static int sample_mixer_byte_array_ctl_put(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+/*
+ *   Byte array payload can be retrieved using:
+ *   void *payload = ev->value.bytes.data;
+ */
+
+    return 0;
+}
+
+static int sample_mixer_tlv_ctl_get(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_tlv *ev)
+{
+    return 0;
+}
+
+static int sample_mixer_tlv_ctl_put(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_tlv *tlv)
+{
+/*
+ *   TLV payload and len can be retrieved using:
+ *   void *payload = &tlv->tlv[0];
+ *   size_t tlv_size = tlv->length;
+ */
+
+    return 0;
+}
+
+static int sample_mixer_enum_ctl_get(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+    return 0;
+}
+
+static int sample_mixer_enum_ctl_put(struct mixer_plugin *plugin,
+                struct snd_control *ctl, struct snd_ctl_elem_value *ev)
+{
+/*
+ *    Enum value can be retrieved using:
+ *    unsigned int val = ev->value.enumerated.item[0];
+ */
+    return 0;
+}
+
+static struct snd_value_int sample_mixer_ctl_value_int =
+    SND_VALUE_INTEGER(3, 0, 1000, 100);
+
+/* 512 max bytes for non-tlv byte controls */
+static struct snd_value_bytes byte_array_ctl_bytes =
+    SND_VALUE_BYTES(512);
+
+static struct snd_value_tlv_bytes sample_mixer_tlv_ctl_bytes =
+    SND_VALUE_TLV_BYTES(1024, sample_mixer_tlv_ctl_get, sample_mixer_tlv_ctl_put);
+
+static void create_integer_ctl(struct sample_mixer_priv *priv,
+                int ctl_idx, int pval, void *pdata)
+{
+    struct snd_control *ctl = SAMPLE_MIXER_PRIV_GET_CTL_PTR(priv, ctl_idx);
+    char *ctl_name = strdup("Sample integer control");
+
+    /* pval and pdata can be retrieved using snd_control during get()/put() */
+    INIT_SND_CONTROL_INTEGER(ctl, ctl_name, sample_mixer_int_ctl_get,
+                    sample_mixer_int_ctl_put, sample_mixer_ctl_value_int, pval, pdata);
+}
+
+static void create_byte_array_ctl(struct sample_mixer_priv *priv,
+    int ctl_idx, int pval, void *pdata)
+{
+    struct snd_control *ctl = SAMPLE_MIXER_PRIV_GET_CTL_PTR(priv, ctl_idx);
+    char *ctl_name = strdup("Sample byte array control");
+
+    INIT_SND_CONTROL_BYTES(ctl, ctl_name, sample_mixer_byte_array_ctl_get,
+            sample_mixer_byte_array_ctl_put, byte_array_ctl_bytes,
+            pval, pdata);
+}
+
+static void create_tlv_ctl(struct sample_mixer_priv *priv,
+                int ctl_idx, int pval, void *pdata)
+{
+    struct snd_control *ctl = SAMPLE_MIXER_PRIV_GET_CTL_PTR(priv, ctl_idx);
+    char *ctl_name = strdup("Sample tlv control");
+
+    INIT_SND_CONTROL_TLV_BYTES(ctl, ctl_name, sample_mixer_tlv_ctl_bytes,
+                    pval, pdata);
+}
+
+static void create_enum_ctl(struct sample_mixer_priv *priv,
+            int ctl_idx, struct snd_value_enum *e,
+            int pval, void *pdata)
+{
+    struct snd_control *ctl = SAMPLE_MIXER_PRIV_GET_CTL_PTR(priv, ctl_idx);
+    char *ctl_name = strdup("Sample enum control");
+
+    INIT_SND_CONTROL_ENUM(ctl, ctl_name, sample_mixer_enum_ctl_get,
+                    sample_mixer_enum_ctl_put, e, pval, pdata);
+}
+
+static int sample_mixer_form_ctls(struct sample_mixer_priv *priv, int ctl_idx)
+{
+    create_integer_ctl(priv, ctl_idx, 0, NULL);
+    ctl_idx++;
+    create_byte_array_ctl(priv, ctl_idx, 0, NULL);
+    ctl_idx++;
+    create_tlv_ctl(priv, ctl_idx, 0, NULL);
+    ctl_idx++;
+    create_enum_ctl(priv, ctl_idx, &priv->sample_enum, 0, NULL);
+    ctl_idx++;
+
+    return 0;
+}
+
+static ssize_t sample_mixer_read_event(struct mixer_plugin *plugin,
+                              struct snd_ctl_event *ev, size_t size)
+{
+    /* Fill snd_ctl_event *ev before sending.
+     * Return : sizeof(struct snd_ctl_event),
+     *          0 in case no event present.
+     */
+
+    return 0;
+}
+
+static int sample_mixer_subscribe_events(struct mixer_plugin *plugin,
+                                  mixer_event_callback event_cb)
+{
+    struct sample_mixer_priv *priv = plugin->priv;
+
+    priv->event_cb = event_cb;
+   /* event_cb is the callback function which needs to be called
+    * when an event occurs. This will unblock poll() on mixer fd
+    * which is called from mixer_wait_event().
+    * Once poll is unblocked, clients can call mixer_read_event()
+    * During unsubscribe(), event_cb is NULL.
+    */
+    return 0;
+}
+
+static int sample_mixer_alloc_ctls(struct sample_mixer_priv *priv)
+{
+    int ret = 0, i;
+
+    priv->ctls = calloc(priv->ctl_count, sizeof(*priv->ctls));
+    if (!priv->ctls) {
+        return -ENOMEM;
+    }
+
+    priv->sample_enum.items = ARRAY_SIZE(sample_enum_text);
+    priv->sample_enum.texts = calloc(priv->sample_enum.items, sizeof(*priv->sample_enum.texts));
+
+    for (i = 0; i < ARRAY_SIZE(sample_enum_text); i++)
+        priv->sample_enum.texts[i] = strdup(sample_enum_text[i]);
+
+    return sample_mixer_form_ctls(priv, 0);
+}
+
+static void sample_mixer_free_ctls(struct sample_mixer_priv *priv)
+{
+    int num_enums, i;
+    struct snd_control *ctl = NULL;
+
+    for (i = 0; i < priv->ctl_count; i++) {
+        ctl = SAMPLE_MIXER_PRIV_GET_CTL_PTR(priv, i);
+        if (ctl->name)
+            free((void *)ctl->name);
+    }
+
+    num_enums = priv->sample_enum.items;
+
+    for (i = 0; i < num_enums; i++)
+        free(priv->sample_enum.texts[i]);
+
+    free(priv->sample_enum.texts);
+    priv->ctl_count = 0;
+
+    if (priv->ctls) {
+        free(priv->ctls);
+        priv->ctls = NULL;
+    }
+}
+
+static void sample_mixer_close(struct mixer_plugin **plugin)
+{
+    struct mixer_plugin *mp = *plugin;
+    struct sample_mixer_priv *priv = mp->priv;
+
+    /* unblock mixer event during close */
+    if (priv->event_cb)
+        priv->event_cb(mp);
+    sample_mixer_subscribe_events(mp, NULL);
+    sample_mixer_free_ctls(priv);
+    free(priv);
+    free(*plugin);
+    *plugin = NULL;
+}
+
+int sample_mixer_open(struct mixer_plugin **plugin, unsigned int card)
+{
+    struct mixer_plugin *mp;
+    struct sample_mixer_priv *priv;
+    int i, ret = 0;
+    int ctl_cnt = 4;
+
+    mp = calloc(1, sizeof(*mp));
+    if (!mp) {
+        return -ENOMEM;
+    }
+
+    priv = calloc(1, sizeof(*priv));
+    if (!priv) {
+        ret = -ENOMEM;
+        goto err_priv_alloc;
+    }
+
+    priv->ctl_count = ctl_cnt;
+    ret = sample_mixer_alloc_ctls(priv);
+    if (ret)
+        goto err_ctls_alloc;
+
+    /* Register the controls */
+    mp->controls = priv->ctls;
+    mp->num_controls = priv->ctl_count;
+    mp->priv = priv;
+    *plugin = mp;
+
+    return 0;
+
+err_ctls_alloc:
+    sample_mixer_free_ctls(priv);
+    free(priv);
+
+err_priv_alloc:
+    free(mp);
+    return ret;
+}
+
+struct mixer_plugin_ops mixer_plugin_ops = {
+    .open = sample_mixer_open,
+    .close = sample_mixer_close,
+    .subscribe_events = sample_mixer_subscribe_events,
+    .read_event = sample_mixer_read_event,
+};