1 files changed, 307 insertions, 0 deletions

diff --git a/dummy/dummy.c b/dummy/dummy.c
new file mode 100644
index 0000000..5f19564
--- /dev/null
+++ b/dummy/dummy.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * Dummy Audio Path for AVIRT
+ * 
+ * Original systimer code:
+ * Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ *
+ * Adapt to use AVIRT
+ * Copyright (c) 2010-2018 Fiberdyne Systems Pty Ltd
+ *  
+ * dummy.c - Dummy Audio Path driver implementation for AVIRT
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <sound/avirt.h>
+
+MODULE_AUTHOR("James O'Shannessy <james.oshannessy@fiberdyne.com.au>");
+MODULE_AUTHOR("Mark Farrugia <mark.farrugia@fiberdyne.com.au>");
+MODULE_DESCRIPTION("Dummy Audio Path for AVIRT");
+MODULE_LICENSE("GPL v2");
+
+#define AP_UID "ap_dummy"
+
+#define AP_INFOK(fmt, args...) DINFO(AP_UID, fmt, ##args)
+#define AP_PRINTK(fmt, args...) DDEBUG(AP_UID, fmt, ##args)
+#define AP_ERRORK(fmt, args...) DERROR(AP_UID, fmt, ##args)
+
+#define DUMMY_SAMPLE_RATE 48000
+#define DUMMY_BLOCKSIZE 512
+#define DUMMY_PERIODS_MIN 1
+#define DUMMY_PERIODS_MAX 8
+
+#define get_dummy_ops(substream) \
+	(*(const struct dummy_timer_ops **)(substream)->runtime->private_data)
+
+static struct snd_avirt_coreinfo *coreinfo;
+
+/*******************************************************************************
+ * System Timer Interface
+ *
+ * This is used to call the ALSA PCM callbacks required to notify AVIRT of the 
+ * 'periods elapsed', so that buffers can keep getting transmitted here
+ * 
+ * (Borrowed from the default ALSA 'dummy' driver (sound/driver/dummy.c))
+ ******************************************************************************/
+struct dummy_timer_ops {
+	int (*create)(struct snd_pcm_substream *);
+	void (*free)(struct snd_pcm_substream *);
+	int (*prepare)(struct snd_pcm_substream *);
+	int (*start)(struct snd_pcm_substream *);
+	int (*stop)(struct snd_pcm_substream *);
+	snd_pcm_uframes_t (*pointer)(struct snd_pcm_substream *);
+};
+
+struct dummy_systimer_pcm {
+	/* ops must be the first item */
+	const struct dummy_timer_ops *timer_ops;
+	spinlock_t lock;
+	struct timer_list timer;
+	unsigned long base_time;
+	unsigned int frac_pos; /* fractional sample position (based HZ) */
+	unsigned int frac_period_rest;
+	unsigned int frac_buffer_size; /* buffer_size * HZ */
+	unsigned int frac_period_size; /* period_size * HZ */
+	unsigned int rate;
+	int elapsed;
+	struct snd_pcm_substream *substream;
+};
+
+static void dummy_systimer_rearm(struct dummy_systimer_pcm *dpcm)
+{
+	mod_timer(&dpcm->timer, jiffies + (dpcm->frac_period_rest + dpcm->rate -
+					   1) / dpcm->rate);
+}
+
+static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm)
+{
+	unsigned long delta;
+
+	delta = jiffies - dpcm->base_time;
+	if (!delta)
+		return;
+	dpcm->base_time += delta;
+	delta *= dpcm->rate;
+	dpcm->frac_pos += delta;
+	while (dpcm->frac_pos >= dpcm->frac_buffer_size)
+		dpcm->frac_pos -= dpcm->frac_buffer_size;
+	while (dpcm->frac_period_rest <= delta) {
+		dpcm->elapsed++;
+		dpcm->frac_period_rest += dpcm->frac_period_size;
+	}
+	dpcm->frac_period_rest -= delta;
+}
+
+static int dummy_systimer_start(struct snd_pcm_substream *substream)
+{
+	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
+	spin_lock(&dpcm->lock);
+	dpcm->base_time = jiffies;
+	dummy_systimer_rearm(dpcm);
+	spin_unlock(&dpcm->lock);
+	return 0;
+}
+
+static int dummy_systimer_stop(struct snd_pcm_substream *substream)
+{
+	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
+	spin_lock(&dpcm->lock);
+	del_timer(&dpcm->timer);
+	spin_unlock(&dpcm->lock);
+	return 0;
+}
+
+static int dummy_systimer_prepare(struct snd_pcm_substream *substream)
+{
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct dummy_systimer_pcm *dpcm = runtime->private_data;
+
+	dpcm->frac_pos = 0;
+	dpcm->rate = runtime->rate;
+	dpcm->frac_buffer_size = runtime->buffer_size * HZ;
+	dpcm->frac_period_size = runtime->period_size * HZ;
+	dpcm->frac_period_rest = dpcm->frac_period_size;
+	dpcm->elapsed = 0;
+
+	return 0;
+}
+
+static void dummy_systimer_callback(struct timer_list *t)
+{
+	struct dummy_systimer_pcm *dpcm = from_timer(dpcm, t, timer);
+	unsigned long flags;
+	int elapsed = 0;
+
+	spin_lock_irqsave(&dpcm->lock, flags);
+	dummy_systimer_update(dpcm);
+	dummy_systimer_rearm(dpcm);
+	elapsed = dpcm->elapsed;
+	dpcm->elapsed = 0;
+	spin_unlock_irqrestore(&dpcm->lock, flags);
+	if (elapsed)
+		snd_avirt_pcm_period_elapsed(dpcm->substream);
+}
+
+static snd_pcm_uframes_t
+	dummy_systimer_pointer(struct snd_pcm_substream *substream)
+{
+	struct dummy_systimer_pcm *dpcm = substream->runtime->private_data;
+	snd_pcm_uframes_t pos;
+
+	spin_lock(&dpcm->lock);
+	dummy_systimer_update(dpcm);
+	pos = dpcm->frac_pos / HZ;
+	spin_unlock(&dpcm->lock);
+	return pos;
+}
+
+static int dummy_systimer_create(struct snd_pcm_substream *substream)
+{
+	struct dummy_systimer_pcm *dpcm;
+
+	dpcm = kzalloc(sizeof(*dpcm), GFP_KERNEL);
+	if (!dpcm)
+		return -ENOMEM;
+	substream->runtime->private_data = dpcm;
+	timer_setup(&dpcm->timer, dummy_systimer_callback, 0);
+	spin_lock_init(&dpcm->lock);
+	dpcm->substream = substream;
+	return 0;
+}
+
+static void dummy_systimer_free(struct snd_pcm_substream *substream)
+{
+	kfree(substream->runtime->private_data);
+}
+
+static const struct dummy_timer_ops dummy_systimer_ops = {
+	.create = dummy_systimer_create,
+	.free = dummy_systimer_free,
+	.prepare = dummy_systimer_prepare,
+	.start = dummy_systimer_start,
+	.stop = dummy_systimer_stop,
+	.pointer = dummy_systimer_pointer,
+};
+
+/*******************************************************************************
+ * Audio Path ALSA PCM Callbacks
+ ******************************************************************************/
+static int dummy_pcm_open(struct snd_pcm_substream *substream)
+{
+	const struct dummy_timer_ops *ops;
+	int err;
+
+	ops = &dummy_systimer_ops;
+	err = ops->create(substream);
+	if (err < 0)
+		return err;
+	get_dummy_ops(substream) = ops;
+
+	return 0;
+}
+
+static int dummy_pcm_close(struct snd_pcm_substream *substream)
+{
+	get_dummy_ops(substream)->free(substream);
+	return 0;
+}
+
+static snd_pcm_uframes_t dummy_pcm_pointer(struct snd_pcm_substream *substream)
+{
+	return get_dummy_ops(substream)->pointer(substream);
+}
+
+static int dummy_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+	case SNDRV_PCM_TRIGGER_RESUME:
+		return get_dummy_ops(substream)->start(substream);
+	case SNDRV_PCM_TRIGGER_STOP:
+	case SNDRV_PCM_TRIGGER_SUSPEND:
+		return get_dummy_ops(substream)->stop(substream);
+	}
+	return -EINVAL;
+}
+
+static int dummy_pcm_prepare(struct snd_pcm_substream *substream)
+{
+	return get_dummy_ops(substream)->prepare(substream);
+}
+
+static struct snd_pcm_ops dummyap_pcm_ops = {
+	.open = dummy_pcm_open,
+	.close = dummy_pcm_close,
+	.prepare = dummy_pcm_prepare,
+	.pointer = dummy_pcm_pointer,
+	.trigger = dummy_pcm_trigger,
+};
+
+/*******************************************************************************
+ * Dummy Audio Path AVIRT registration
+ ******************************************************************************/
+static int dummy_configure(struct snd_card *card,
+			   struct config_group *snd_avirt_stream_group,
+			   unsigned int stream_count)
+{
+	// Do something with streams
+
+	struct list_head *entry;
+	list_for_each (entry, &snd_avirt_stream_group->cg_children) {
+		struct config_item *item =
+			container_of(entry, struct config_item, ci_entry);
+		struct snd_avirt_stream *stream =
+			snd_avirt_stream_from_config_item(item);
+		AP_INFOK("stream name:%s device:%d channels:%d", stream->name,
+			 stream->device, stream->channels);
+	}
+
+	return 0;
+}
+
+static struct snd_pcm_hardware dummyap_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 = DUMMY_SAMPLE_RATE,
+	.rate_max = DUMMY_SAMPLE_RATE,
+	.periods_min = DUMMY_PERIODS_MIN,
+	.periods_max = DUMMY_PERIODS_MAX,
+};
+
+static struct snd_avirt_audiopath dummyap_module = {
+	.uid = "ap_dummy",
+	.name = "Dummy Audio Path",
+	.version = { 0, 0, 1 },
+	.hw = &dummyap_hw,
+	.pcm_ops = &dummyap_pcm_ops,
+	.configure = dummy_configure,
+};
+
+static int __init dummy_init(void)
+{
+	int err = 0;
+
+	pr_info("init()\n");
+
+	err = snd_avirt_audiopath_register(&dummyap_module, &coreinfo);
+	if ((err < 0) || (!coreinfo)) {
+		pr_err("%s: coreinfo is NULL!\n", __func__);
+		return err;
+	}
+
+	return err;
+}
+
+static void __exit dummy_exit(void)
+{
+	pr_info("exit()\n");
+
+	snd_avirt_audiopath_deregister(&dummyap_module);
+}
+
+module_init(dummy_init);
+module_exit(dummy_exit);