Staging: most: add MOST driver's aim-sound module

This patch adds the aim-sound module of the MOST driver to the kernel's
driver staging area. This module is part of the MOST driver and handles
user space interaction by means of ALSA devices.

This patch is needed in order to have access to MOST synchronous data
through ALSA devices.
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/Kconfig

@@ -17,4 +17,6 @@ source "drivers/staging/most/aim-cdev/Kconfig"
 
 source "drivers/staging/most/aim-network/Kconfig"
 
+source "drivers/staging/most/aim-sound/Kconfig"
+
 endif

drivers/staging/most/Makefile

 obj-$(CONFIG_MOSTCORE)	+= mostcore/
 obj-$(CONFIG_AIM_CDEV)	+= aim-cdev/
 obj-$(CONFIG_AIM_NETWORK)	+= aim-network/
+obj-$(CONFIG_AIM_SOUND)	+= aim-sound/

drivers/staging/most/aim-sound/Kconfig

+#
+# MOST ALSA configuration
+#
+
+config AIM_SOUND
+	tristate "ALSA AIM"
+	depends on SND
+	---help---
+	  Say Y here if you want to commumicate via ALSA/sound devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called aim_sound.

drivers/staging/most/aim-sound/Makefile

+obj-$(CONFIG_AIM_SOUND) += aim_sound.o
+
+aim_sound-objs := sound.o
+ccflags-y += -Idrivers/staging/most/mostcore/

drivers/staging/most/aim-sound/sound.c

+/*
+ * sound.c - Audio Application Interface Module for Mostcore
+ *
+ * Copyright (C) 2015 Microchip Technology Germany II GmbH & Co. KG
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * This file is licensed under GPLv2.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <linux/sched.h>
+#include <linux/kthread.h>
+#include <mostcore.h>
+
+#define DRIVER_NAME "sound"
+
+static struct list_head dev_list;
+
+/**
+ * struct channel - private structure to keep channel specific data
+ * @substream: stores the substream structure
+ * @iface: interface for which the channel belongs to
+ * @cfg: channel configuration
+ * @card: registered sound card
+ * @list: list for private use
+ * @id: channel index
+ * @period_pos: current period position (ring buffer)
+ * @buffer_pos: current buffer position (ring buffer)
+ * @is_stream_running: identifies whether a stream is running or not
+ * @opened: set when the stream is opened
+ * @playback_task: playback thread
+ * @playback_waitq: waitq used by playback thread
+ */
+struct channel {
+	struct snd_pcm_substream *substream;
+	struct most_interface *iface;
+	struct most_channel_config *cfg;
+	struct snd_card *card;
+	struct list_head list;
+	int id;
+	unsigned int period_pos;
+	unsigned int buffer_pos;
+	bool is_stream_running;
+
+	struct task_struct *playback_task;
+	wait_queue_head_t playback_waitq;
+
+	void (*copy_fn)(void *alsa, void *most, unsigned int bytes);
+};
+
+#define MOST_PCM_INFO (SNDRV_PCM_INFO_MMAP | \
+		       SNDRV_PCM_INFO_MMAP_VALID | \
+		       SNDRV_PCM_INFO_BATCH | \
+		       SNDRV_PCM_INFO_INTERLEAVED | \
+		       SNDRV_PCM_INFO_BLOCK_TRANSFER)
+
+/**
+ * Initialization of struct snd_pcm_hardware
+ */
+static struct snd_pcm_hardware pcm_hardware_template = {
+	.info               = MOST_PCM_INFO,
+	.rates              = SNDRV_PCM_RATE_48000,
+	.rate_min           = 48000,
+	.rate_max           = 48000,
+	.channels_min       = 1,
+	.channels_max       = 8,
+};
+
+#define swap16(val) ( \
+	(((u16)(val) << 8) & (u16)0xFF00) | \
+	(((u16)(val) >> 8) & (u16)0x00FF))
+
+#define swap32(val) ( \
+	(((u32)(val) << 24) & (u32)0xFF000000) | \
+	(((u32)(val) <<  8) & (u32)0x00FF0000) | \
+	(((u32)(val) >>  8) & (u32)0x0000FF00) | \
+	(((u32)(val) >> 24) & (u32)0x000000FF))
+
+static void swap_copy16(u16 *dest, const u16 *source, unsigned int bytes)
+{
+	unsigned int i = 0;
+
+	while (i < (bytes / 2)) {
+		dest[i] = swap16(source[i]);
+		i++;
+	}
+}
+
+static void swap_copy24(u8 *dest, const u8 *source, unsigned int bytes)
+{
+	unsigned int i = 0;
+
+	while (i < bytes - 2) {
+		dest[i] = source[i + 2];
+		dest[i + 1] = source[i + 1];
+		dest[i + 2] = source[i];
+		i += 3;
+	}
+}
+
+static void swap_copy32(u32 *dest, const u32 *source, unsigned int bytes)
+{
+	unsigned int i = 0;
+
+	while (i < bytes / 4) {
+		dest[i] = swap32(source[i]);
+		i++;
+	}
+}
+
+static void alsa_to_most_memcpy(void *alsa, void *most, unsigned int bytes)
+{
+	memcpy(most, alsa, bytes);
+}
+
+static void alsa_to_most_copy16(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy16(most, alsa, bytes);
+}
+
+static void alsa_to_most_copy24(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy24(most, alsa, bytes);
+}
+
+static void alsa_to_most_copy32(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy32(most, alsa, bytes);
+}
+
+static void most_to_alsa_memcpy(void *alsa, void *most, unsigned int bytes)
+{
+	memcpy(alsa, most, bytes);
+}
+
+static void most_to_alsa_copy16(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy16(alsa, most, bytes);
+}
+
+static void most_to_alsa_copy24(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy24(alsa, most, bytes);
+}
+
+static void most_to_alsa_copy32(void *alsa, void *most, unsigned int bytes)
+{
+	swap_copy32(alsa, most, bytes);
+}
+
+/**
+ * get_channel - get pointer to channel
+ * @iface: interface structure
+ * @channel_id: channel ID
+ *
+ * This traverses the channel list and returns the channel matching the
+ * ID and interface.
+ *
+ * Returns pointer to channel on success or NULL otherwise.
+ */
+static struct channel *get_channel(struct most_interface *iface,
+				   int channel_id)
+{
+	struct channel *channel, *tmp;
+
+	list_for_each_entry_safe(channel, tmp, &dev_list, list) {
+		if ((channel->iface == iface) && (channel->id == channel_id))
+			return channel;
+	}
+
+	return NULL;
+}
+
+/**
+ * copy_data - implements data copying function
+ * @channel: channel
+ * @mbo: MBO from core
+ *
+ * Copy data from/to ring buffer to/from MBO and update the buffer position
+ */
+static bool copy_data(struct channel *channel, struct mbo *mbo)
+{
+	struct snd_pcm_runtime *const runtime = channel->substream->runtime;
+	unsigned int const frame_bytes = channel->cfg->subbuffer_size;
+	unsigned int const buffer_size = runtime->buffer_size;
+	unsigned int frames;
+	unsigned int fr0;
+
+	if (channel->cfg->direction & MOST_CH_RX)
+		frames = mbo->processed_length / frame_bytes;
+	else
+		frames = mbo->buffer_length / frame_bytes;
+	fr0 = min(buffer_size - channel->buffer_pos, frames);
+
+	channel->copy_fn(runtime->dma_area + channel->buffer_pos * frame_bytes,
+			 mbo->virt_address,
+			 fr0 * frame_bytes);
+
+	if (frames > fr0) {
+		/* wrap around at end of ring buffer */
+		channel->copy_fn(runtime->dma_area,
+				 mbo->virt_address + fr0 * frame_bytes,
+				 (frames - fr0) * frame_bytes);
+	}
+
+	channel->buffer_pos += frames;
+	if (channel->buffer_pos >= buffer_size)
+		channel->buffer_pos -= buffer_size;
+	channel->period_pos += frames;
+	if (channel->period_pos >= runtime->period_size) {
+		channel->period_pos -= runtime->period_size;
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * playback_thread - function implements the playback thread
+ * @data: private data
+ *
+ * Thread which does the playback functionality in a loop. It waits for a free
+ * MBO from mostcore for a particular channel and copy the data from ring buffer
+ * to MBO. Submit the MBO back to mostcore, after copying the data.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int playback_thread(void *data)
+{
+	struct channel *const channel = data;
+
+	pr_info("playback thread started\n");
+
+	while (!kthread_should_stop()) {
+		struct mbo *mbo = NULL;
+		bool period_elapsed = false;
+		int ret;
+
+		wait_event_interruptible(
+			channel->playback_waitq,
+			kthread_should_stop() ||
+			(mbo = most_get_mbo(channel->iface, channel->id)));
+
+		if (!mbo)
+			continue;
+
+		if (channel->is_stream_running)
+			period_elapsed = copy_data(channel, mbo);
+		else
+			memset(mbo->virt_address, 0, mbo->buffer_length);
+
+		ret = most_submit_mbo(mbo);
+		if (ret)
+			channel->is_stream_running = false;
+
+		if (period_elapsed)
+			snd_pcm_period_elapsed(channel->substream);
+	}
+
+	return 0;
+}
+
+/**
+ * pcm_open - implements open callback function for PCM middle layer
+ * @substream: pointer to ALSA PCM substream
+ *
+ * This is called when a PCM substream is opened. At least, the function should
+ * initialize the runtime->hw record.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_open(struct snd_pcm_substream *substream)
+{
+	struct channel *channel = substream->private_data;
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct most_channel_config *cfg = channel->cfg;
+
+	pr_info("pcm_open(), %s\n", substream->name);
+
+	channel->substream = substream;
+
+	if (cfg->direction == MOST_CH_TX) {
+		init_waitqueue_head(&channel->playback_waitq);
+		channel->playback_task = kthread_run(&playback_thread, channel,
+						     "most_audio_playback");
+		if (IS_ERR(channel->playback_task))
+			return PTR_ERR(channel->playback_task);
+	}
+
+	if (most_start_channel(channel->iface, channel->id)) {
+		pr_err("most_start_channel() failed!\n");
+		if (cfg->direction == MOST_CH_TX)
+			kthread_stop(channel->playback_task);
+		return -EBUSY;
+	}
+
+	runtime->hw = pcm_hardware_template;
+	runtime->hw.buffer_bytes_max = cfg->num_buffers * cfg->buffer_size;
+	runtime->hw.period_bytes_min = cfg->buffer_size;
+	runtime->hw.period_bytes_max = cfg->buffer_size;
+	runtime->hw.periods_min = 1;
+	runtime->hw.periods_max = cfg->num_buffers;
+
+	return 0;
+}
+
+/**
+ * pcm_close - implements close callback function for PCM middle layer
+ * @substream: sub-stream pointer
+ *
+ * Obviously, this is called when a PCM substream is closed. Any private
+ * instance for a PCM substream allocated in the open callback will be
+ * released here.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_close(struct snd_pcm_substream *substream)
+{
+	struct channel *channel = substream->private_data;
+
+	pr_info("pcm_close(), %s\n", substream->name);
+
+	if (channel->cfg->direction == MOST_CH_TX)
+		kthread_stop(channel->playback_task);
+	most_stop_channel(channel->iface, channel->id);
+
+	return 0;
+}
+
+/**
+ * pcm_hw_params - implements hw_params callback function for PCM middle layer
+ * @substream: sub-stream pointer
+ * @hw_params: contains the hardware parameters set by the application
+ *
+ * This is called when the hardware parameters is set by the application, that
+ * is, once when the buffer size, the period size, the format, etc. are defined
+ * for the PCM substream. Many hardware setups should be done is this callback,
+ * including the allocation of buffers.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_hw_params(struct snd_pcm_substream *substream,
+			 struct snd_pcm_hw_params *hw_params)
+{
+	pr_info("pcm_hw_params()\n");
+
+	return snd_pcm_lib_alloc_vmalloc_buffer(substream,
+						params_buffer_bytes(hw_params));
+}
+
+/**
+ * pcm_hw_free - implements hw_free callback function for PCM middle layer
+ * @substream: substream pointer
+ *
+ * This is called to release the resources allocated via hw_params.
+ * This function will be always called before the close callback is called.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_hw_free(struct snd_pcm_substream *substream)
+{
+	pr_info("pcm_hw_free()\n");
+
+	return snd_pcm_lib_free_vmalloc_buffer(substream);
+}
+
+/**
+ * pcm_prepare - implements prepare callback function for PCM middle layer
+ * @substream: substream pointer
+ *
+ * This callback is called when the PCM is "prepared". Format rate, sample rate,
+ * etc., can be set here. This callback can be called many times at each setup.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_prepare(struct snd_pcm_substream *substream)
+{
+	struct channel *channel = substream->private_data;
+	struct snd_pcm_runtime *runtime = substream->runtime;
+	struct most_channel_config *cfg = channel->cfg;
+	int width = snd_pcm_format_physical_width(runtime->format);
+
+	channel->copy_fn = NULL;
+
+	if (cfg->direction == MOST_CH_TX) {
+		if (snd_pcm_format_big_endian(runtime->format) || width == 8)
+			channel->copy_fn = alsa_to_most_memcpy;
+		else if (width == 16)
+			channel->copy_fn = alsa_to_most_copy16;
+		else if (width == 24)
+			channel->copy_fn = alsa_to_most_copy24;
+		else if (width == 32)
+			channel->copy_fn = alsa_to_most_copy32;
+	} else {
+		if (snd_pcm_format_big_endian(runtime->format) || width == 8)
+			channel->copy_fn = most_to_alsa_memcpy;
+		else if (width == 16)
+			channel->copy_fn = most_to_alsa_copy16;
+		else if (width == 24)
+			channel->copy_fn = most_to_alsa_copy24;
+		else if (width == 32)
+			channel->copy_fn = most_to_alsa_copy32;
+	}
+
+	if (!channel->copy_fn) {
+		pr_err("unsupported format\n");
+		return -EINVAL;
+	}
+
+	channel->period_pos = 0;
+	channel->buffer_pos = 0;
+
+	return 0;
+}
+
+/**
+ * pcm_trigger - implements trigger callback function for PCM middle layer
+ * @substream: substream pointer
+ * @cmd: action to perform
+ *
+ * This is called when the PCM is started, stopped or paused. The action will be
+ * specified in the second argument, SNDRV_PCM_TRIGGER_XXX
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	struct channel *channel = substream->private_data;
+
+	switch (cmd) {
+	case SNDRV_PCM_TRIGGER_START:
+		channel->is_stream_running = true;
+		return 0;
+
+	case SNDRV_PCM_TRIGGER_STOP:
+		channel->is_stream_running = false;
+		return 0;
+
+	default:
+		pr_info("pcm_trigger(), invalid\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+/**
+ * pcm_pointer - implements pointer callback function for PCM middle layer
+ * @substream: substream pointer
+ *
+ * This callback is called when the PCM middle layer inquires the current
+ * hardware position on the buffer. The position must be returned in frames,
+ * ranging from 0 to buffer_size-1.
+ */
+static snd_pcm_uframes_t pcm_pointer(struct snd_pcm_substream *substream)
+{
+	struct channel *channel = substream->private_data;
+
+	return channel->buffer_pos;
+}
+
+/**
+ * Initialization of struct snd_pcm_ops
+ */
+static struct snd_pcm_ops pcm_ops = {
+	.open       = pcm_open,
+	.close      = pcm_close,
+	.ioctl      = snd_pcm_lib_ioctl,
+	.hw_params  = pcm_hw_params,
+	.hw_free    = pcm_hw_free,
+	.prepare    = pcm_prepare,
+	.trigger    = pcm_trigger,
+	.pointer    = pcm_pointer,
+	.page       = snd_pcm_lib_get_vmalloc_page,
+	.mmap       = snd_pcm_lib_mmap_vmalloc,
+};
+
+
+int split_arg_list(char *buf, char **card_name, char **pcm_format)
+{
+	*card_name = strsep(&buf, ".");
+	if (!*card_name)
+		return -EIO;
+	*pcm_format = strsep(&buf, ".\n");
+	if (!*pcm_format)
+		return -EIO;
+	return 0;
+}
+
+int audio_set_pcm_format(char *pcm_format, struct most_channel_config *cfg)
+{
+	if (!strcmp(pcm_format, "1x8")) {
+		if (cfg->subbuffer_size != 1)
+			goto error;
+		pr_info("PCM format is 8-bit mono\n");
+		pcm_hardware_template.formats = SNDRV_PCM_FMTBIT_S8;
+	} else if (!strcmp(pcm_format, "2x16")) {
+		if (cfg->subbuffer_size != 4)
+			goto error;
+		pr_info("PCM format is 16-bit stereo\n");
+		pcm_hardware_template.formats = SNDRV_PCM_FMTBIT_S16_LE |
+						SNDRV_PCM_FMTBIT_S16_BE;
+	} else if (!strcmp(pcm_format, "2x24")) {
+		if (cfg->subbuffer_size != 6)
+			goto error;
+		pr_info("PCM format is 24-bit stereo\n");
+		pcm_hardware_template.formats = SNDRV_PCM_FMTBIT_S24_3LE |
+						SNDRV_PCM_FMTBIT_S24_3BE;
+	} else if (!strcmp(pcm_format, "2x32")) {
+		if (cfg->subbuffer_size != 8)
+			goto error;
+		pr_info("PCM format is 32-bit stereo\n");
+		pcm_hardware_template.formats = SNDRV_PCM_FMTBIT_S32_LE |
+						SNDRV_PCM_FMTBIT_S32_BE;
+	} else {
+		pr_err("PCM format %s not supported\n", pcm_format);
+		return -EIO;
+	}
+	return 0;
+error:
+	pr_err("Audio resolution doesn't fit subbuffer size\n");
+	return -EINVAL;
+}
+
+/**
+ * audio_probe_channel - probe function of the driver module
+ * @iface: pointer to interface instance
+ * @channel_id: channel index/ID
+ * @cfg: pointer to actual channel configuration
+ * @parent: pointer to kobject (needed for sysfs hook-up)
+ * @arg_list: string that provides the name of the device to be created in /dev
+ *	      plus the desired audio resolution
+ *
+ * Creates sound card, pcm device, sets pcm ops and registers sound card.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int audio_probe_channel(struct most_interface *iface, int channel_id,
+			       struct most_channel_config *cfg,
+			       struct kobject *parent, char *arg_list)
+{
+	struct channel *channel;
+	struct snd_card *card;
+	struct snd_pcm *pcm;
+	int playback_count = 0;
+	int capture_count = 0;
+	int ret;
+	int direction;
+	char *card_name;
+	char *pcm_format;
+
+	pr_info("sound_probe_channel()\n");
+
+	if (!iface)
+		return -EINVAL;
+
+	if (cfg->data_type != MOST_CH_SYNC) {
+		pr_err("Incompatible channel type\n");
+		return -EINVAL;
+	}
+
+	if (get_channel(iface, channel_id)) {
+		pr_err("channel (%s:%d) is already linked\n",
+		       iface->description, channel_id);
+		return -EINVAL;
+	}
+
+	if (cfg->direction == MOST_CH_TX) {
+		playback_count = 1;
+		direction = SNDRV_PCM_STREAM_PLAYBACK;
+	} else {
+		capture_count = 1;
+		direction = SNDRV_PCM_STREAM_CAPTURE;
+	}
+
+	ret = split_arg_list(arg_list, &card_name, &pcm_format);
+	if (ret < 0) {
+		pr_info("PCM format missing\n");
+		return ret;
+	}
+	if (audio_set_pcm_format(pcm_format, cfg))
+		return ret;
+
+	ret = snd_card_new(NULL, -1, card_name, THIS_MODULE,
+			   sizeof(*channel), &card);
+	if (ret < 0)
+		return ret;
+
+	channel = card->private_data;
+	channel->card = card;
+	channel->cfg = cfg;
+	channel->iface = iface;
+	channel->id = channel_id;
+
+	snprintf(card->driver, sizeof(card->driver), "%s", DRIVER_NAME);
+	snprintf(card->shortname, sizeof(card->shortname), "MOST:%d",
+		 card->number);
+	snprintf(card->longname, sizeof(card->longname), "%s at %s, ch %d",
+		 card->shortname, iface->description, channel_id);
+
+	ret = snd_pcm_new(card, card_name, 0, playback_count,
+			  capture_count, &pcm);
+	if (ret < 0)
+		goto err_free_card;
+
+	pcm->private_data = channel;
+
+	snd_pcm_set_ops(pcm, direction, &pcm_ops);
+
+	ret = snd_card_register(card);
+	if (ret < 0)
+		goto err_free_card;
+
+	list_add_tail(&channel->list, &dev_list);
+
+	return 0;
+
+err_free_card:
+	snd_card_free(card);
+	return ret;
+}
+
+/**
+ * audio_disconnect_channel - function to disconnect a channel
+ * @iface: pointer to interface instance
+ * @channel_id: channel index
+ *
+ * This frees allocated memory and removes the sound card from ALSA
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int audio_disconnect_channel(struct most_interface *iface,
+				    int channel_id)
+{
+	struct channel *channel;
+
+	pr_info("sound_disconnect_channel()\n");
+
+	channel = get_channel(iface, channel_id);
+	if (!channel) {
+		pr_err("sound_disconnect_channel(), invalid channel %d\n",
+		       channel_id);
+		return -EINVAL;
+	}
+
+	list_del(&channel->list);
+	snd_card_free(channel->card);
+
+	return 0;
+}
+
+/**
+ * audio_rx_completion - completion handler for rx channels
+ * @mbo: pointer to buffer object that has completed
+ *
+ * This searches for the channel this MBO belongs to and copy the data from MBO
+ * to ring buffer
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int audio_rx_completion(struct mbo *mbo)
+{
+	struct channel *channel = get_channel(mbo->ifp, mbo->hdm_channel_id);
+	bool period_elapsed = false;
+
+	if (!channel) {
+		pr_err("sound_rx_completion(), invalid channel %d\n",
+		       mbo->hdm_channel_id);
+		return -EINVAL;
+	}
+
+	if (channel->is_stream_running)
+		period_elapsed = copy_data(channel, mbo);
+
+	most_put_mbo(mbo);
+
+	if (period_elapsed)
+		snd_pcm_period_elapsed(channel->substream);
+
+	return 0;
+}
+
+/**
+ * audio_tx_completion - completion handler for tx channels
+ * @iface: pointer to interface instance
+ * @channel_id: channel index/ID
+ *
+ * This searches the channel that belongs to this combination of interface
+ * pointer and channel ID and wakes a process sitting in the wait queue of
+ * this channel.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int audio_tx_completion(struct most_interface *iface, int channel_id)
+{
+	struct channel *channel = get_channel(iface, channel_id);
+
+	if (!channel) {
+		pr_err("sound_tx_completion(), invalid channel %d\n",
+		       channel_id);
+		return -EINVAL;
+	}
+
+	wake_up_interruptible(&channel->playback_waitq);
+
+	return 0;
+}
+
+/**
+ * Initialization of the struct most_aim
+ */
+static struct most_aim audio_aim = {
+	.name = DRIVER_NAME,
+	.probe_channel = audio_probe_channel,
+	.disconnect_channel = audio_disconnect_channel,
+	.rx_completion = audio_rx_completion,
+	.tx_completion = audio_tx_completion,
+};
+
+static int __init audio_init(void)
+{
+	pr_info("init()\n");
+
+	INIT_LIST_HEAD(&dev_list);
+
+	return most_register_aim(&audio_aim);
+}
+
+static void __exit audio_exit(void)
+{
+	struct channel *channel, *tmp;
+
+	pr_info("exit()\n");
+
+	list_for_each_entry_safe(channel, tmp, &dev_list, list) {
+		list_del(&channel->list);
+		snd_card_free(channel->card);
+	}
+
+	most_deregister_aim(&audio_aim);
+}
+
+module_init(audio_init);
+module_exit(audio_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Gromm <christian.gromm@microchip.com>");
+MODULE_DESCRIPTION("Audio Application Interface Module for MostCore");