tinyalsa: add support for PCM plugins

Update the pcm framework to support plugins. Resolve the pcm device node
to be either kernel device or virtual device and setup function pointers
accordingly. Implement framework functionality for pcm_plugin.c for ease
of plugin development. Plugin itself is compiled as shared object (.so)
and dynamically linked from pcm_plugin.c.

Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>
Signed-off-by: Rohit kumar <rohitkr@codeaurora.org>

1 files changed, 149 insertions, 0 deletions

diff --git a/src/snd_card_plugin.c b/src/snd_card_plugin.c
new file mode 100644
index 0000000..17912a2
--- /dev/null
+++ b/src/snd_card_plugin.c
@@ -0,0 +1,149 @@
+/* snd_card_plugin.c
+** Copyright (c) 2019, The Linux Foundation.
+**
+** 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 "snd_card_plugin.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#define SND_DLSYM(h, p, s, err) \
+do {                            \
+    err = 0;                    \
+    p = dlsym(h, s);            \
+    if (!p)                        \
+        err = -ENODEV;            \
+} while(0)
+
+int snd_utils_get_int(struct snd_node *node, const char *prop, int *val)
+{
+    if (!node || !node->card_node || !node->dev_node)
+        return SND_NODE_TYPE_HW;
+
+    return node->ops->get_int(node->dev_node, prop, val);
+}
+
+int snd_utils_get_str(struct snd_node *node, const char *prop, char **val)
+{
+    if (!node || !node->card_node || !node->dev_node)
+        return SND_NODE_TYPE_HW;
+
+    return node->ops->get_str(node->dev_node, prop, val);
+}
+
+void snd_utils_close_dev_node(struct snd_node *node)
+{
+    if (!node)
+        return;
+
+    if (node->card_node)
+        node->ops->close_card(node->card_node);
+
+    if (node->dl_hdl)
+        dlclose(node->dl_hdl);
+
+    free(node);
+}
+
+enum snd_node_type snd_utils_get_node_type(struct snd_node *node)
+{
+    int val = SND_NODE_TYPE_HW;
+
+    if (!node || !node->card_node || !node->dev_node)
+        return SND_NODE_TYPE_HW;
+
+    node->ops->get_int(node->dev_node, "type", &val);
+
+    return val;
+};
+
+static int snd_utils_resolve_symbols(struct snd_node *node)
+{
+    void *dl = node->dl_hdl;
+    int err;
+    SND_DLSYM(dl, node->ops, "snd_card_ops", err);
+    return err;
+}
+
+static struct snd_node *snd_utils_open_dev_node(unsigned int card,
+                                                unsigned int device,
+                                                int dev_type)
+{
+    struct snd_node *node;
+    int rc = 0;
+
+    node = calloc(1, sizeof(*node));
+    if (!node)
+        return NULL;
+
+    node->dl_hdl = dlopen("libsndcardparser.so", RTLD_NOW);
+    if (!node->dl_hdl) {
+        goto err_dl_open;
+    }
+
+    rc = snd_utils_resolve_symbols(node);
+    if (rc < 0)
+        goto err_resolve_symbols;
+
+    node->card_node = node->ops->open_card(card);
+    if (!node->card_node)
+        goto err_resolve_symbols;
+
+    if (dev_type == NODE_PCM) {
+      node->dev_node = node->ops->get_pcm(node->card_node, device);
+    } else {
+      node->dev_node = node->ops->get_mixer(node->card_node);
+    }
+
+    if (!node->dev_node)
+        goto err_get_node;
+
+    return node;
+
+err_get_node:
+    node->ops->close_card(node->card_node);
+
+err_resolve_symbols:
+    dlclose(node->dl_hdl);
+
+err_dl_open:
+    free(node);
+    return NULL;
+}
+
+struct snd_node* snd_utils_open_pcm(unsigned int card,
+                                    unsigned int device)
+{
+  return snd_utils_open_dev_node(card, device, NODE_PCM);
+}
+
+struct snd_node* snd_utils_open_mixer(unsigned int card)
+{
+  return snd_utils_open_dev_node(card, 0, NODE_MIXER);
+}