tinyalsa: Add sample pcm/mixer plugin and sample sndcardparser

6 files changed, 947 insertions, 0 deletions

diff --git a/Android.bp b/Android.bp
index d6fec57..a36a923 100644
--- a/Android.bp
+++ b/Android.bp
@@ -63,6 +63,12 @@ cc_library {
     },
 }
 
+cc_library_headers {
+    name: "libtinyalsav2_headers",
+    export_include_dirs: ["include"],
+    vendor_available: true,
+}
+
 cc_binary {
     name: "tinyplay2",
     host_supported: true,
diff --git a/examples/plugins/Android.bp b/examples/plugins/Android.bp
new file mode 100644
index 0000000..840480e
--- /dev/null
+++ b/examples/plugins/Android.bp
@@ -0,0 +1,15 @@
+cc_library {
+    name: "libtinyalsav2_example_plugin_pcm",
+    vendor: true,
+    srcs: ["sample_pcm_plugin.c"],
+    cflags: ["-Werror", "-Wno-unused-parameter"],
+    header_libs: ["libtinyalsav2_headers"],
+}
+
+cc_library {
+    name: "libtinyalsav2_example_plugin_mixer",
+    vendor: true,
+    srcs: ["sample_mixer_plugin.c"],
+    cflags: ["-Werror", "-Wno-unused-parameter"],
+    header_libs: ["libtinyalsav2_headers"],
+}
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,
+};
diff --git a/examples/plugins/sample_pcm_plugin.c b/examples/plugins/sample_pcm_plugin.c
new file mode 100644
index 0000000..3b02435
--- /dev/null
+++ b/examples/plugins/sample_pcm_plugin.c
@@ -0,0 +1,331 @@
+/*
+** 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 <limits.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+#include <sound/asound.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <tinyalsa/plugin.h>
+#include <tinyalsa/asoundlib.h>
+
+/* 2 words of uint32_t = 64 bits of mask */
+#define PCM_MASK_SIZE (2)
+#define PCM_FORMAT_BIT(x) (1ULL << x)
+
+struct sample_pcm_priv {
+    FILE *fptr;
+    int session_id;
+    int channels;
+    int bitwidth;
+    int sample_rate;
+    unsigned int period_size;
+    snd_pcm_uframes_t total_size_frames;
+};
+
+struct pcm_plugin_hw_constraints sample_pcm_constrs = {
+    .access = 0,
+    .format = 0,
+    .bit_width = {
+        .min = 16,
+        .max = 32,
+    },
+    .channels = {
+        .min = 1,
+        .max = 8,
+    },
+    .rate = {
+        .min = 8000,
+        .max = 384000,
+    },
+    .periods = {
+        .min = 1,
+        .max = 8,
+    },
+    .period_bytes = {
+        .min = 96,
+        .max = 122880,
+    },
+};
+
+static inline struct snd_interval *param_to_interval(struct snd_pcm_hw_params *p,
+                                                  int n)
+{
+    return &(p->intervals[n - SNDRV_PCM_HW_PARAM_FIRST_INTERVAL]);
+}
+
+static inline int param_is_interval(int p)
+{
+    return (p >= SNDRV_PCM_HW_PARAM_FIRST_INTERVAL) &&
+        (p <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL);
+}
+
+static unsigned int param_get_int(struct snd_pcm_hw_params *p, int n)
+{
+    if (param_is_interval(n)) {
+        struct snd_interval *i = param_to_interval(p, n);
+        if (i->integer)
+            return i->max;
+    }
+    return 0;
+}
+
+static inline struct snd_mask *param_to_mask(struct snd_pcm_hw_params *p, int n)
+{
+    return &(p->masks[n - SNDRV_PCM_HW_PARAM_FIRST_MASK]);
+}
+
+static inline int param_is_mask(int p)
+{
+    return (p >= SNDRV_PCM_HW_PARAM_FIRST_MASK) &&
+        (p <= SNDRV_PCM_HW_PARAM_LAST_MASK);
+}
+
+static inline int snd_mask_val(const struct snd_mask *mask)
+{
+    int i;
+    for (i = 0; i < PCM_MASK_SIZE; i++) {
+        if (mask->bits[i])
+            return ffs(mask->bits[i]) + (i << 5) - 1;
+    }
+    return 0;
+}
+
+static int alsaformat_to_bitwidth(int format)
+{
+    switch (format) {
+    case SNDRV_PCM_FORMAT_S32_LE:
+    case SNDRV_PCM_FORMAT_S24_LE:
+        return 32;
+    case SNDRV_PCM_FORMAT_S8:
+        return 8;
+    case SNDRV_PCM_FORMAT_S24_3LE:
+        return 24;
+    default:
+    case SNDRV_PCM_FORMAT_S16_LE:
+        return 16;
+    };
+}
+
+static int param_get_mask_val(struct snd_pcm_hw_params *p,
+                                        int n)
+{
+    if (param_is_mask(n)) {
+        struct snd_mask *m = param_to_mask(p, n);
+        int val = snd_mask_val(m);
+
+        return alsaformat_to_bitwidth(val);
+    }
+    return 0;
+}
+
+static int sample_session_open(int sess_id, unsigned int mode, struct sample_pcm_priv *priv)
+{
+     char fname[128];
+
+     snprintf(fname, 128, "sample_pcm_data_%d.raw", sess_id);
+     priv->fptr = fopen(fname,"rwb+");
+     if (priv->fptr == NULL) {
+         return -EIO;
+     }
+     rewind(priv->fptr);
+     return 0;
+}
+
+
+static int sample_session_write(struct sample_pcm_priv *priv, void *buff, size_t count)
+{
+    uint8_t *data = (uint8_t *)buff;
+    size_t len;
+
+    len  = fwrite(buff, 1, count, priv->fptr);
+
+    if (len != count)
+        return -EIO;
+
+    return 0;
+}
+
+static int sample_pcm_hw_params(struct pcm_plugin *plugin,
+                             struct snd_pcm_hw_params *params)
+{
+    struct sample_pcm_priv *priv = plugin->priv;
+
+    priv->sample_rate = param_get_int(params, SNDRV_PCM_HW_PARAM_RATE);
+    priv->channels = param_get_int(params, SNDRV_PCM_HW_PARAM_CHANNELS);
+    priv->bitwidth = param_get_mask_val(params, SNDRV_PCM_HW_PARAM_FORMAT);
+
+    return 0;
+}
+
+static int sample_pcm_sw_params(struct pcm_plugin *plugin,
+                             struct snd_pcm_sw_params *sparams)
+{
+    return 0;
+}
+
+static int sample_pcm_sync_ptr(struct pcm_plugin *plugin,
+                            struct snd_pcm_sync_ptr *sync_ptr)
+{
+    return 0;
+}
+
+static int sample_pcm_writei_frames(struct pcm_plugin *plugin, struct snd_xferi *x)
+{
+    struct sample_pcm_priv *priv = plugin->priv;
+    void *buff;
+    size_t count;
+
+    buff = x->buf;
+    count = x->frames * (priv->channels * (priv->bitwidth) / 8);
+
+    return sample_session_write(priv, buff, count);
+}
+
+static int sample_pcm_readi_frames(struct pcm_plugin *plugin, struct snd_xferi *x)
+{
+    return 0;
+}
+
+static int sample_pcm_ttstamp(struct pcm_plugin *plugin, int *tstamp)
+{
+    return 0;
+}
+
+static int sample_pcm_prepare(struct pcm_plugin *plugin)
+{
+    return 0;
+}
+
+static int sample_pcm_start(struct pcm_plugin *plugin)
+{
+    return 0;
+}
+
+static int sample_pcm_drop(struct pcm_plugin *plugin)
+{
+    return 0;
+}
+
+static int sample_pcm_close(struct pcm_plugin *plugin)
+{
+    struct sample_pcm_priv *priv = plugin->priv;
+    int ret = 0;
+
+    fclose(priv->fptr);
+    free(plugin->priv);
+    free(plugin);
+
+    return ret;
+}
+
+static int sample_pcm_poll(struct pcm_plugin *plugin, struct pollfd *pfd,
+        nfds_t nfds, int timeout)
+{
+    return 0;
+}
+
+static void* sample_pcm_mmap(struct pcm_plugin *plugin, void *addr, size_t length, int prot,
+                               int flags, off_t offset)
+{
+    return MAP_FAILED;
+}
+
+static int sample_pcm_munmap(struct pcm_plugin *plugin, void *addr, size_t length)
+{
+    return 0;
+}
+
+int sample_pcm_open(struct pcm_plugin **plugin, unsigned int card,
+                    unsigned int device, unsigned int mode)
+{
+    struct pcm_plugin *sample_pcm_plugin;
+    struct sample_pcm_priv *priv;
+    int ret = 0, session_id = device;
+
+    sample_pcm_plugin = calloc(1, sizeof(struct pcm_plugin));
+    if (!sample_pcm_plugin)
+        return -ENOMEM;
+
+    priv = calloc(1, sizeof(struct sample_pcm_priv));
+    if (!priv) {
+        ret = -ENOMEM;
+        goto err_plugin_free;
+    }
+
+    sample_pcm_constrs.access = (PCM_FORMAT_BIT(SNDRV_PCM_ACCESS_RW_INTERLEAVED) |
+                              PCM_FORMAT_BIT(SNDRV_PCM_ACCESS_RW_NONINTERLEAVED));
+    sample_pcm_constrs.format = (PCM_FORMAT_BIT(SNDRV_PCM_FORMAT_S16_LE) |
+                              PCM_FORMAT_BIT(SNDRV_PCM_FORMAT_S24_LE) |
+                              PCM_FORMAT_BIT(SNDRV_PCM_FORMAT_S24_3LE) |
+                              PCM_FORMAT_BIT(SNDRV_PCM_FORMAT_S32_LE));
+
+    sample_pcm_plugin->card = card;
+    sample_pcm_plugin->mode = mode;
+    sample_pcm_plugin->constraints = &sample_pcm_constrs;
+    sample_pcm_plugin->priv = priv;
+
+    priv->session_id = session_id;
+
+    ret = sample_session_open(session_id, mode, priv);
+    if (ret) {
+        errno = -ret;
+        goto err_priv_free;
+    }
+    *plugin = sample_pcm_plugin;
+    return 0;
+
+err_priv_free:
+    free(priv);
+err_plugin_free:
+    free(sample_pcm_plugin);
+    return ret;
+}
+
+struct pcm_plugin_ops pcm_plugin_ops = {
+    .open = sample_pcm_open,
+    .close = sample_pcm_close,
+    .hw_params = sample_pcm_hw_params,
+    .sw_params = sample_pcm_sw_params,
+    .sync_ptr = sample_pcm_sync_ptr,
+    .writei_frames = sample_pcm_writei_frames,
+    .readi_frames = sample_pcm_readi_frames,
+    .ttstamp = sample_pcm_ttstamp,
+    .prepare = sample_pcm_prepare,
+    .start = sample_pcm_start,
+    .drop = sample_pcm_drop,
+    .mmap = sample_pcm_mmap,
+    .munmap = sample_pcm_munmap,
+    .poll = sample_pcm_poll,
+};
diff --git a/examples/sndcardparser/Android.bp b/examples/sndcardparser/Android.bp
new file mode 100644
index 0000000..9ca8812
--- /dev/null
+++ b/examples/sndcardparser/Android.bp
@@ -0,0 +1,7 @@
+cc_library {
+    name: "libsndcardparser_example",
+    vendor: true,
+    srcs: ["sample_sndcardparser.c"],
+    cflags: ["-Werror"],
+}
+
diff --git a/examples/sndcardparser/sample_sndcardparser.c b/examples/sndcardparser/sample_sndcardparser.c
new file mode 100644
index 0000000..90e3d12
--- /dev/null
+++ b/examples/sndcardparser/sample_sndcardparser.c
@@ -0,0 +1,269 @@
+/*
+** 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 <stdlib.h>
+#include <string.h>
+
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+
+#define VIRTUAL_SND_CARD_ID 100
+#define MAX_PATH 256
+#define BUF_SIZE 1024
+
+enum snd_node_type {
+    NODE_TYPE_HW = 0,
+    NODE_TYPE_PLUGIN,
+    NODE_TYPE_INVALID,
+};
+
+enum {
+    NODE_PCM,
+    NODE_COMPR,
+    NODE_MIXER,
+    NODE_MAX,
+};
+
+struct snd_node_ops {
+    /** Function pointer to get card definition */
+    void* (*open_card)(unsigned int card);
+    /** Function pointer to release card definition */
+    void (*close_card)(void *card);
+    /** Get interger type properties from device definition */
+    int (*get_int)(void *node, const char *prop, int *val);
+    /** Get string type properties from device definition */
+    int (*get_str)(void *node, const char *prop, char **val);
+    /** Function pointer to get mixer definition */
+    void* (*get_mixer)(void *card);
+    /** Function pointer to get PCM definition */
+    void* (*get_pcm)(void *card, unsigned int id);
+    /** Function pointer to get COMPRESS definition */
+    void* (*get_compress)(void *card, unsigned int id);
+};
+
+struct snd_dev_def {
+    unsigned int device;
+    int type;
+    const char *name;
+    const char *so_name;
+    int playback; //used only for pcm node
+    int capture;  //used only for pcm node
+    /* add custom props here */
+};
+
+struct snd_dev_def_card {
+    unsigned int card;
+    char *name;
+
+    /* child device details */
+    int num_pcm_nodes;
+    struct snd_dev_def *pcm_dev_def;
+
+    struct snd_dev_def *mixer_dev_def;
+};
+
+struct snd_dev_def pcm_devs[] = {
+    {100, NODE_TYPE_PLUGIN, "PCM100", "libtinyalsav2_example_plugin_pcm.so", 1, 0},
+    /* Add other plugin info here */
+};
+
+struct snd_dev_def mixer_dev =
+    {VIRTUAL_SND_CARD_ID, NODE_TYPE_PLUGIN, "virtual-snd-card", "libtinyalsav2_example_plugin_mixer.so", 0, 0};
+
+void *snd_card_def_open_card(unsigned int card)
+{
+    struct snd_dev_def_card *card_def = NULL;
+    struct snd_dev_def *pcm_dev_def = NULL;
+    struct snd_dev_def *mixer_dev_def = NULL;
+    int num_pcm = ARRAY_SIZE(pcm_devs);
+    int i;
+
+    if (card != VIRTUAL_SND_CARD_ID)
+        return NULL;
+
+    card_def = calloc(1, sizeof(struct snd_dev_def_card));
+    if (!card_def)
+        return card_def;
+
+    card_def->card = card;
+    card_def->name = strdup("virtual-snd-card");
+
+    /* fill pcm device node info */
+    card_def->num_pcm_nodes = num_pcm;
+    pcm_dev_def = calloc(num_pcm, sizeof(struct snd_dev_def));
+    if (!pcm_dev_def)
+        goto free_card_def;
+
+    for (i = 0; i < num_pcm; i++)
+        memcpy(&pcm_dev_def[i], &pcm_devs[i], sizeof(struct snd_dev_def));
+
+    card_def->pcm_dev_def = pcm_dev_def;
+
+    /* fill mixer device node info */
+    mixer_dev_def = calloc(1, sizeof(struct snd_dev_def));
+    if (!mixer_dev_def)
+        goto free_pcm_dev;
+
+    memcpy(mixer_dev_def, &mixer_dev, sizeof(struct snd_dev_def));
+
+    card_def->mixer_dev_def = mixer_dev_def;
+    return card_def;
+free_pcm_dev:
+    free(pcm_dev_def);
+free_card_def:
+    free(card_def->name);
+    free(card_def);
+    return NULL;
+}
+
+void snd_card_def_close_card(void *card_node)
+{
+    struct snd_dev_def_card *defs = (struct snd_dev_def_card *)card_node;
+    struct snd_dev_def *pcm_dev_def = NULL;
+    struct snd_dev_def *mixer_dev_def = NULL;
+
+    if (!defs)
+        return;
+
+    pcm_dev_def = defs->pcm_dev_def;
+    if (pcm_dev_def)
+        free(pcm_dev_def);
+
+    mixer_dev_def = defs->mixer_dev_def;
+    if (!mixer_dev_def)
+         goto free_defs;
+
+    free(mixer_dev_def);
+free_defs:
+    free(defs->name);
+    free(defs);
+}
+
+void *snd_card_def_get_node(void *card_node, unsigned int id, int type)
+{
+    struct snd_dev_def_card *card_def = (struct snd_dev_def_card *)card_node;
+    struct snd_dev_def *dev_def = NULL;
+    int i;
+
+    if (!card_def)
+        return NULL;
+
+    if (type >= NODE_MAX)
+        return NULL;
+
+    if (type == NODE_MIXER)
+        return card_def->mixer_dev_def;
+
+    if (type == NODE_PCM)
+        dev_def = card_def->pcm_dev_def;
+
+    for (i = 0; i < card_def->num_pcm_nodes; i++) {
+        if (dev_def[i].device == id) {
+            return &dev_def[i];
+        }
+    }
+
+    return NULL;
+}
+
+int snd_card_def_get_int(void *node, const char *prop, int *val)
+{
+    struct snd_dev_def *dev_def = (struct snd_dev_def *)node;
+    int ret = -EINVAL;
+
+    if (!dev_def || !prop || !val)
+        return ret;
+
+    if (!strcmp(prop, "type")) {
+        *val = dev_def->type;
+        return 0;
+    } else if (!strcmp(prop, "id")) {
+        *val = dev_def->device;
+        return 0;
+    } else if (!strcmp(prop, "playback")) {
+        *val = dev_def->playback;
+        return 0;
+    } else if (!strcmp(prop, "capture")) {
+        *val = dev_def->capture;
+        return 0;
+    }
+
+    return ret;
+}
+
+int snd_card_def_get_str(void *node, const char *prop, char **val)
+{
+    struct snd_dev_def *dev_def = (struct snd_dev_def *)node;
+    int ret = -EINVAL;
+
+    if (!dev_def || !prop)
+        return ret;
+
+    if (!strcmp(prop, "so-name")) {
+        if (dev_def->so_name) {
+            *val = (char *)dev_def->so_name;
+            return 0;
+        }
+    }
+
+    if (!strcmp(prop, "name")) {
+        if (dev_def->name) {
+            *val = (char *)dev_def->name;
+            return 0;
+        }
+    }
+
+    return ret;
+}
+
+void *snd_card_def_get_pcm(void *card_node, unsigned int id)
+{
+    return snd_card_def_get_node(card_node, id, NODE_PCM);
+}
+
+void *snd_card_def_get_compress(void *card_node, unsigned int id)
+{
+    return snd_card_def_get_node(card_node, id, NODE_COMPR);
+}
+
+void *snd_card_def_get_mixer(void *card_node)
+{
+    return snd_card_def_get_node(card_node, 1, NODE_MIXER);
+}
+
+struct snd_node_ops snd_card_ops = {
+    .open_card = snd_card_def_open_card,
+    .close_card = snd_card_def_close_card,
+    .get_int = snd_card_def_get_int,
+    .get_str = snd_card_def_get_str,
+    .get_pcm = snd_card_def_get_pcm,
+    .get_compress = snd_card_def_get_compress,
+    .get_mixer = snd_card_def_get_mixer,
+};