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, 154 insertions, 0 deletions

diff --git a/include/tinyalsa/plugin.h b/include/tinyalsa/plugin.h
new file mode 100644
index 0000000..87bdaa0
--- /dev/null
+++ b/include/tinyalsa/plugin.h
@@ -0,0 +1,154 @@
+/* plugin.h
+** Copyright (c) 2019-2020, 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.
+**/
+
+#ifndef TINYALSA_PLUGIN_H
+#define TINYALSA_PLUGIN_H
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <sound/asound.h>
+ * entry point function.
+ * @ingroup libtinyalsa-pcm
+ */
+#define PCM_PLUGIN_OPEN_FN_PTR()                        \
+    int (*plugin_open_fn) (struct pcm_plugin **plugin,  \
+                           unsigned int card,           \
+                           unsigned int device,         \
+                           int mode);
+/** Forward declaration of the structure to hold pcm
+ * plugin related data/information.
+ */
+struct pcm_plugin;
+struct snd_node;
+
+/** Operations that are required to be registered by the plugin.
+ * @ingroup libtinyalsa-pcm
+ */
+struct pcm_plugin_ops {
+    /** open the pcm plugin */
+    int (*open) (struct pcm_plugin **plugin, unsigned int card,
+                 unsigned int device, unsigned int flags);
+    /** close the pcm plugin */
+    int (*close) (struct pcm_plugin *plugin);
+    /** Set the PCM hardware parameters to the plugin */
+    int (*hw_params) (struct pcm_plugin *plugin,
+                      struct snd_pcm_hw_params *params);
+    /** Set the PCM software parameters to the plugin */
+    int (*sw_params) (struct pcm_plugin *plugin,
+                      struct snd_pcm_sw_params *params);
+    /** Synchronize the pointer */
+    int (*sync_ptr) (struct pcm_plugin *plugin,
+                     struct snd_pcm_sync_ptr *sync_ptr);
+    /** Write frames to plugin to be rendered to output */
+    int (*writei_frames) (struct pcm_plugin *plugin,
+                          struct snd_xferi *x);
+    /** Read frames from plugin captured from input */
+    int (*readi_frames) (struct pcm_plugin *plugin,
+                         struct snd_xferi *x);
+    /** Obtain the timestamp for the PCM */
+    int (*ttstamp) (struct pcm_plugin *plugin,
+                    int *tstamp);
+    /** Prepare the plugin for data transfer */
+    int (*prepare) (struct pcm_plugin *plugin);
+    /** Start data transfer from/to the plugin */
+    int (*start) (struct pcm_plugin *plugin);
+    /** Drop pcm frames */
+    int (*drop) (struct pcm_plugin *plugin);
+    /** Any custom or alsa specific ioctl implementation */
+    int (*ioctl) (struct pcm_plugin *plugin,
+                  int cmd, void *arg);
+};
+
+/** Minimum and maximum values for hardware parameter constraints.
+ * @ingroup libtinyalsa-pcm
+ */
+struct pcm_plugin_min_max {
+    /** Minimum value for the hardware parameter */
+    unsigned int min;
+    /** Maximum value for the hardware parameter */
+    unsigned int max;
+};
+
+/** Encapsulate the hardware parameter constraints
+ * @ingroup libtinyalsa-pcm
+ */
+struct pcm_plugin_hw_constraints {
+    /** Value for SNDRV_PCM_HW_PARAM_ACCESS param */
+    uint64_t access;
+    /** Value for SNDRV_PCM_HW_PARAM_FORMAT param.
+     * As of this implementation ALSA supports 52 formats */
+    uint64_t format;
+    /** Value for SNDRV_PCM_HW_PARAM_SAMPLE_BITS param */
+    struct pcm_plugin_min_max bit_width;
+    /** Value for SNDRV_PCM_HW_PARAM_CHANNELS param */
+    struct pcm_plugin_min_max channels;
+    /** Value for SNDRV_PCM_HW_PARAM_RATE param */
+    struct pcm_plugin_min_max rate;
+    /** Value for SNDRV_PCM_HW_PARAM_PERIODS param */
+    struct pcm_plugin_min_max periods;
+    /** Value for SNDRV_PCM_HW_PARAM_PERIOD_BYTES param */
+    struct pcm_plugin_min_max period_bytes;
+};
+
+struct pcm_plugin {
+    /** Card number for the pcm device */
+    unsigned int card;
+    /** device number for the pcm device */
+    unsigned int device;
+    /** pointer to the contraints registered by the plugin */
+    struct pcm_plugin_hw_constraints *constraints;
+    /** Indicates read/write mode, etc.. */
+    int mode;
+    /* Pointer to hold the plugin's private data */
+    void *priv;
+    /* Tracks the plugin state */
+    unsigned int state;
+};
+
+
+/** Operations defined by the plugin.
+ * */
+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);
+    /** Reserved for other nodes such as compress */
+    void* reserved[4];
+};
+#endif /* end of TINYALSA_PLUGIN_H */