Adding groundwork for loopback

Added a skeleton for the loopback audiopath.

Signed-off-by: James O'Shannessy <james.oshannessy@fiberdyne.com.au>

1 files changed, 112 insertions, 0 deletions

diff --git a/loopback/loopback.c b/loopback/loopback.c
new file mode 100644
index 0000000..57f3c34
--- /dev/null
+++ b/loopback/loopback.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ALSA Virtual Soundcard
+ *
+ * loopback_audiopath.c - AVIRT sample Audio Path definition
+ *
+ * Copyright (C) 2010-2018 Fiberdyne Systems Pty Ltd
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <avirt/core.h>
+
+MODULE_AUTHOR("JOSHANNE <james.oshannessy@fiberdyne.com.au>");
+MODULE_AUTHOR("MFARRUGI <mark.farrugia@fiberdyne.com.au>");
+MODULE_DESCRIPTION("Sample Audio Path Module Interface");
+MODULE_LICENSE("GPL v2");
+
+static struct avirt_coreinfo *coreinfo;
+
+/*******************************************************************************
+ * Audio Path ALSA PCM Callbacks
+ ******************************************************************************/
+static int loopback_pcm_open(struct snd_pcm_substream *substream)
+{
+	return 0;
+}
+
+static int loopback_pcm_close(struct snd_pcm_substream *substream)
+{
+	return 0;
+}
+
+static snd_pcm_uframes_t
+	loopback_pcm_pointer(struct snd_pcm_substream *substream)
+{
+	return 0;
+}
+
+static int loopback_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+	case SNDRV_PCM_TRIGGER_RESUME:
+	case SNDRV_PCM_TRIGGER_STOP:
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+		return 0;
+	}
+	return -EINVAL;
+}
+
+static int loopback_pcm_prepare(struct snd_pcm_substream *substream)
+{
+	return 0;
+}
+
+static struct snd_pcm_ops loopbackap_pcm_ops = {
+	.open = loopback_pcm_open,
+	.close = loopback_pcm_close,
+	.prepare = loopback_pcm_prepare,
+	.pointer = loopback_pcm_pointer,
+	.trigger = loopback_pcm_trigger,
+};
+
+/*******************************************************************************
+ * Loopback Audio Path AVIRT registration
+ ******************************************************************************/
+static struct snd_pcm_hardware loopbackap_hw = {
+	.formats = SNDRV_PCM_FMTBIT_S16_LE,
+	.info = (SNDRV_PCM_INFO_INTERLEAVED // Channel interleaved audio
+		 | SNDRV_PCM_INFO_BLOCK_TRANSFER | SNDRV_PCM_INFO_MMAP |
+		 SNDRV_PCM_INFO_MMAP_VALID),
+	.rates = SNDRV_PCM_RATE_48000,
+	.rate_min = 48000,
+	.rate_max = 48000,
+	.periods_min = 1,
+	.periods_max = 8,
+};
+
+static struct avirt_audiopath loopbackap_module = {
+	.name = "Loopback Audio Path",
+	.version = { 0, 0, 1 },
+	.value = 10,
+	.hw = &loopbackap_hw,
+	.pcm_ops = &loopbackap_pcm_ops,
+	.blocksize = 512,
+};
+
+static int __init loopback_init(void)
+{
+	int err = 0;
+
+	pr_info("init()\n");
+
+	err = avirt_register_audiopath(&loopbackap_module, &coreinfo);
+	if ((err < 0) || (!coreinfo)) {
+		pr_err("%s: coreinfo is NULL!\n", __func__);
+		return err;
+	}
+
+	return err;
+}
+
+static void __exit loopback_exit(void)
+{
+	pr_info("exit()\n");
+
+	avirt_deregister_audiopath(&loopbackap_module);
+}
+
+module_init(loopback_init);
+module_exit(loopback_exit);