drivers/most/most_snd.c - kernel/common - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * sound.c - Sound component for Mostcore
  *
  * Copyright (C) 2015 Microchip Technology Germany II GmbH & Co. KG
  */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/module.h>
 #include <linux/printk.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
 #include <sound/pcm_params.h>
 #include <linux/sched.h>
 #include <linux/kthread.h>
 #include <linux/most.h>

 #define DRIVER_NAME "sound"
 #define STRING_SIZE	80

 static struct most_component comp;

 /**
  * 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 snd_pcm_hardware pcm_hardware;
 	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);
 };

 struct sound_adapter {
 	struct list_head dev_list;
 	struct most_interface *iface;
 	struct snd_card *card;
 	struct list_head list;
 	bool registered;
 	int pcm_dev_idx;
 };

 static struct list_head adpt_list;

 #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)

 static void swap_copy16(u16 *dest, const u16 *source, unsigned int bytes)
 {
 	unsigned int i = 0;

 	while (i < (bytes / 2)) {
 		dest[i] = swab16(source[i]);
 		i++;
 	}
 }

 static void swap_copy24(u8 *dest, const u8 *source, unsigned int bytes)
 {
 	unsigned int i = 0;

 	if (bytes < 2)
 		return;
 	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] = swab32(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 sound_adapter *adpt = iface->priv;
 	struct channel *channel;

 	list_for_each_entry(channel, &adpt->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;

 	while (!kthread_should_stop()) {
 		struct mbo *mbo = NULL;
 		bool period_elapsed = false;

 		wait_event_interruptible(
 			channel->playback_waitq,
 			kthread_should_stop() ||
 			(channel->is_stream_running &&
 			 (mbo = most_get_mbo(channel->iface, channel->id,
 					     &comp))));
 		if (!mbo)
 			continue;

 		if (channel->is_stream_running)
 			period_elapsed = copy_data(channel, mbo);
 		else
 			memset(mbo->virt_address, 0, mbo->buffer_length);

 		most_submit_mbo(mbo);
 		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;
 	int ret;

 	channel->substream = substream;

 	if (cfg->direction == MOST_CH_TX) {
 		channel->playback_task = kthread_run(playback_thread, channel,
 						     "most_audio_playback");
 		if (IS_ERR(channel->playback_task)) {
 			pr_err("Couldn't start thread\n");
 			return PTR_ERR(channel->playback_task);
 		}
 	}

 	ret = most_start_channel(channel->iface, channel->id, &comp);
 	if (ret) {
 		pr_err("most_start_channel() failed!\n");
 		if (cfg->direction == MOST_CH_TX)
 			kthread_stop(channel->playback_task);
 		return ret;
 	}

 	runtime->hw = channel->pcm_hardware;
 	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;

 	if (channel->cfg->direction == MOST_CH_TX)
 		kthread_stop(channel->playback_task);
 	most_stop_channel(channel->iface, channel->id, &comp);
 	return 0;
 }

 /**
  * 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)
 		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;
 		wake_up_interruptible(&channel->playback_waitq);
 		return 0;

 	case SNDRV_PCM_TRIGGER_STOP:
 		channel->is_stream_running = false;
 		return 0;

 	default:
 		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 const struct snd_pcm_ops pcm_ops = {
 	.open       = pcm_open,
 	.close      = pcm_close,
 	.prepare    = pcm_prepare,
 	.trigger    = pcm_trigger,
 	.pointer    = pcm_pointer,
 };

 static int split_arg_list(char *buf, u16 *ch_num, char **sample_res)
 {
 	char *num;
 	int ret;

 	num = strsep(&buf, "x");
 	if (!num)
 		goto err;
 	ret = kstrtou16(num, 0, ch_num);
 	if (ret)
 		goto err;
 	*sample_res = strsep(&buf, ".\n");
 	if (!*sample_res)
 		goto err;
 	return 0;

 err:
 	pr_err("Bad PCM format\n");
 	return -EINVAL;
 }

 static const struct sample_resolution_info {
 	const char *sample_res;
 	int bytes;
 	u64 formats;
 } sinfo[] = {
 	{ "8", 1, SNDRV_PCM_FMTBIT_S8 },
 	{ "16", 2, SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S16_BE },
 	{ "24", 3, SNDRV_PCM_FMTBIT_S24_3LE | SNDRV_PCM_FMTBIT_S24_3BE },
 	{ "32", 4, SNDRV_PCM_FMTBIT_S32_LE | SNDRV_PCM_FMTBIT_S32_BE },
 };

 static int audio_set_hw_params(struct snd_pcm_hardware *pcm_hw,
 			       u16 ch_num, char *sample_res,
 			       struct most_channel_config *cfg)
 {
 	int i;

 	for (i = 0; i < ARRAY_SIZE(sinfo); i++) {
 		if (!strcmp(sample_res, sinfo[i].sample_res))
 			goto found;
 	}
 	pr_err("Unsupported PCM format\n");
 	return -EINVAL;

 found:
 	if (!ch_num) {
 		pr_err("Bad number of channels\n");
 		return -EINVAL;
 	}

 	if (cfg->subbuffer_size != ch_num * sinfo[i].bytes) {
 		pr_err("Audio resolution doesn't fit subbuffer size\n");
 		return -EINVAL;
 	}

 	pcm_hw->info = MOST_PCM_INFO;
 	pcm_hw->rates = SNDRV_PCM_RATE_48000;
 	pcm_hw->rate_min = 48000;
 	pcm_hw->rate_max = 48000;
 	pcm_hw->buffer_bytes_max = cfg->num_buffers * cfg->buffer_size;
 	pcm_hw->period_bytes_min = cfg->buffer_size;
 	pcm_hw->period_bytes_max = cfg->buffer_size;
 	pcm_hw->periods_min = 1;
 	pcm_hw->periods_max = cfg->num_buffers;
 	pcm_hw->channels_min = ch_num;
 	pcm_hw->channels_max = ch_num;
 	pcm_hw->formats = sinfo[i].formats;
 	return 0;
 }

 static void release_adapter(struct sound_adapter *adpt)
 {
 	struct channel *channel, *tmp;

 	list_for_each_entry_safe(channel, tmp, &adpt->dev_list, list) {
 		list_del(&channel->list);
 		kfree(channel);
 	}
 	if (adpt->card)
 		snd_card_free(adpt->card);
 	list_del(&adpt->list);
 	kfree(adpt);
 }

 /**
  * 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
  * @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,
 			       char *device_name, char *arg_list)
 {
 	struct channel *channel;
 	struct sound_adapter *adpt;
 	struct snd_pcm *pcm;
 	int playback_count = 0;
 	int capture_count = 0;
 	int ret;
 	int direction;
 	u16 ch_num;
 	char *sample_res;
 	char arg_list_cpy[STRING_SIZE];

 	if (cfg->data_type != MOST_CH_SYNC) {
 		pr_err("Incompatible channel type\n");
 		return -EINVAL;
 	}
 	strscpy(arg_list_cpy, arg_list, STRING_SIZE);
 	ret = split_arg_list(arg_list_cpy, &ch_num, &sample_res);
 	if (ret < 0)
 		return ret;

 	list_for_each_entry(adpt, &adpt_list, list) {
 		if (adpt->iface != iface)
 			continue;
 		if (adpt->registered)
 			return -ENOSPC;
 		adpt->pcm_dev_idx++;
 		goto skip_adpt_alloc;
 	}
 	adpt = kzalloc(sizeof(*adpt), GFP_KERNEL);
 	if (!adpt)
 		return -ENOMEM;

 	adpt->iface = iface;
 	INIT_LIST_HEAD(&adpt->dev_list);
 	iface->priv = adpt;
 	list_add_tail(&adpt->list, &adpt_list);
 	ret = snd_card_new(iface->driver_dev, -1, "INIC", THIS_MODULE,
 			   sizeof(*channel), &adpt->card);
 	if (ret < 0)
 		goto err_free_adpt;
 	snprintf(adpt->card->driver, sizeof(adpt->card->driver),
 		 "%s", DRIVER_NAME);
 	snprintf(adpt->card->shortname, sizeof(adpt->card->shortname),
 		 "Microchip INIC");
 	snprintf(adpt->card->longname, sizeof(adpt->card->longname),
 		 "%s at %s", adpt->card->shortname, iface->description);
 skip_adpt_alloc:
 	if (get_channel(iface, channel_id)) {
 		pr_err("channel (%s:%d) is already linked\n",
 		       iface->description, channel_id);
 		return -EEXIST;
 	}

 	if (cfg->direction == MOST_CH_TX) {
 		playback_count = 1;
 		direction = SNDRV_PCM_STREAM_PLAYBACK;
 	} else {
 		capture_count = 1;
 		direction = SNDRV_PCM_STREAM_CAPTURE;
 	}
 	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
 	if (!channel) {
 		ret = -ENOMEM;
 		goto err_free_adpt;
 	}
 	channel->card = adpt->card;
 	channel->cfg = cfg;
 	channel->iface = iface;
 	channel->id = channel_id;
 	init_waitqueue_head(&channel->playback_waitq);
 	list_add_tail(&channel->list, &adpt->dev_list);

 	ret = audio_set_hw_params(&channel->pcm_hardware, ch_num, sample_res,
 				  cfg);
 	if (ret)
 		goto err_free_adpt;

 	ret = snd_pcm_new(adpt->card, device_name, adpt->pcm_dev_idx,
 			  playback_count, capture_count, &pcm);

 	if (ret < 0)
 		goto err_free_adpt;

 	pcm->private_data = channel;
 	strscpy(pcm->name, device_name, sizeof(pcm->name));
 	snd_pcm_set_ops(pcm, direction, &pcm_ops);
 	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, NULL, 0, 0);
 	return 0;

 err_free_adpt:
 	release_adapter(adpt);
 	return ret;
 }

 static int audio_create_sound_card(void)
 {
 	int ret;
 	struct sound_adapter *adpt;

 	list_for_each_entry(adpt, &adpt_list, list) {
 		if (!adpt->registered)
 			goto adpt_alloc;
 	}
 	return -ENODEV;
 adpt_alloc:
 	ret = snd_card_register(adpt->card);
 	if (ret < 0) {
 		release_adapter(adpt);
 		return ret;
 	}
 	adpt->registered = true;
 	return 0;
 }

 /**
  * 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;
 	struct sound_adapter *adpt = iface->priv;

 	channel = get_channel(iface, channel_id);
 	if (!channel)
 		return -EINVAL;

 	list_del(&channel->list);

 	kfree(channel);
 	if (list_empty(&adpt->dev_list))
 		release_adapter(adpt);
 	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)
 		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)
 		return -EINVAL;

 	wake_up_interruptible(&channel->playback_waitq);
 	return 0;
 }

 /**
  * Initialization of the struct most_component
  */
 static struct most_component comp = {
 	.mod = THIS_MODULE,
 	.name = DRIVER_NAME,
 	.probe_channel = audio_probe_channel,
 	.disconnect_channel = audio_disconnect_channel,
 	.rx_completion = audio_rx_completion,
 	.tx_completion = audio_tx_completion,
 	.cfg_complete = audio_create_sound_card,
 };

 static int __init audio_init(void)
 {
 	int ret;

 	INIT_LIST_HEAD(&adpt_list);

 	ret = most_register_component(&comp);
 	if (ret) {
 		pr_err("Failed to register %s\n", comp.name);
 		return ret;
 	}
 	ret = most_register_configfs_subsys(&comp);
 	if (ret) {
 		pr_err("Failed to register %s configfs subsys\n", comp.name);
 		most_deregister_component(&comp);
 	}
 	return ret;
 }

 static void __exit audio_exit(void)
 {
 	most_deregister_configfs_subsys(&comp);
 	most_deregister_component(&comp);
 }

 module_init(audio_init);
 module_exit(audio_exit);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Christian Gromm <[email protected]>");
 MODULE_DESCRIPTION("Sound Component Module for Mostcore");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* sound.c - Sound component for Mostcore
	*
	* Copyright (C) 2015 Microchip Technology Germany II GmbH & Co. KG
	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/module.h>
	#include <linux/printk.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <sound/core.h>
	#include <sound/pcm.h>
	#include <sound/pcm_params.h>
	#include <linux/sched.h>
	#include <linux/kthread.h>
	#include <linux/most.h>

	#define DRIVER_NAME "sound"
	#define STRING_SIZE 80

	static struct most_component comp;

	/**
	* 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 snd_pcm_hardware pcm_hardware;
	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);
	};

	struct sound_adapter {
	struct list_head dev_list;
	struct most_interface *iface;
	struct snd_card *card;
	struct list_head list;
	bool registered;
	int pcm_dev_idx;
	};

	static struct list_head adpt_list;

	#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)

	static void swap_copy16(u16 dest, const u16 source, unsigned int bytes)
	{
	unsigned int i = 0;

	while (i < (bytes / 2)) {
	dest[i] = swab16(source[i]);
	i++;
	}
	}

	static void swap_copy24(u8 dest, const u8 source, unsigned int bytes)
	{
	unsigned int i = 0;

	if (bytes < 2)
	return;
	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] = swab32(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 sound_adapter *adpt = iface->priv;
	struct channel *channel;

	list_for_each_entry(channel, &adpt->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;

	while (!kthread_should_stop()) {
	struct mbo *mbo = NULL;
	bool period_elapsed = false;

	wait_event_interruptible(
	channel->playback_waitq,
	kthread_should_stop() \|\|
	(channel->is_stream_running &&
	(mbo = most_get_mbo(channel->iface, channel->id,
	&comp))));
	if (!mbo)
	continue;

	if (channel->is_stream_running)
	period_elapsed = copy_data(channel, mbo);
	else
	memset(mbo->virt_address, 0, mbo->buffer_length);

	most_submit_mbo(mbo);
	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;
	int ret;

	channel->substream = substream;

	if (cfg->direction == MOST_CH_TX) {
	channel->playback_task = kthread_run(playback_thread, channel,
	"most_audio_playback");
	if (IS_ERR(channel->playback_task)) {
	pr_err("Couldn't start thread\n");
	return PTR_ERR(channel->playback_task);
	}
	}

	ret = most_start_channel(channel->iface, channel->id, &comp);
	if (ret) {
	pr_err("most_start_channel() failed!\n");
	if (cfg->direction == MOST_CH_TX)
	kthread_stop(channel->playback_task);
	return ret;
	}

	runtime->hw = channel->pcm_hardware;
	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;

	if (channel->cfg->direction == MOST_CH_TX)
	kthread_stop(channel->playback_task);
	most_stop_channel(channel->iface, channel->id, &comp);
	return 0;
	}

	/**
	* 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)
	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;
	wake_up_interruptible(&channel->playback_waitq);
	return 0;

	case SNDRV_PCM_TRIGGER_STOP:
	channel->is_stream_running = false;
	return 0;

	default:
	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 const struct snd_pcm_ops pcm_ops = {
	.open = pcm_open,
	.close = pcm_close,
	.prepare = pcm_prepare,
	.trigger = pcm_trigger,
	.pointer = pcm_pointer,
	};

	static int split_arg_list(char buf, u16 ch_num, char **sample_res)
	{
	char *num;
	int ret;

	num = strsep(&buf, "x");
	if (!num)
	goto err;
	ret = kstrtou16(num, 0, ch_num);
	if (ret)
	goto err;
	*sample_res = strsep(&buf, ".\n");
	if (!*sample_res)
	goto err;
	return 0;

	err:
	pr_err("Bad PCM format\n");
	return -EINVAL;
	}

	static const struct sample_resolution_info {
	const char *sample_res;
	int bytes;
	u64 formats;
	} sinfo[] = {
	{ "8", 1, SNDRV_PCM_FMTBIT_S8 },
	{ "16", 2, SNDRV_PCM_FMTBIT_S16_LE \| SNDRV_PCM_FMTBIT_S16_BE },
	{ "24", 3, SNDRV_PCM_FMTBIT_S24_3LE \| SNDRV_PCM_FMTBIT_S24_3BE },
	{ "32", 4, SNDRV_PCM_FMTBIT_S32_LE \| SNDRV_PCM_FMTBIT_S32_BE },
	};

	static int audio_set_hw_params(struct snd_pcm_hardware *pcm_hw,
	u16 ch_num, char *sample_res,
	struct most_channel_config *cfg)
	{
	int i;

	for (i = 0; i < ARRAY_SIZE(sinfo); i++) {
	if (!strcmp(sample_res, sinfo[i].sample_res))
	goto found;
	}
	pr_err("Unsupported PCM format\n");
	return -EINVAL;

	found:
	if (!ch_num) {
	pr_err("Bad number of channels\n");
	return -EINVAL;
	}

	if (cfg->subbuffer_size != ch_num * sinfo[i].bytes) {
	pr_err("Audio resolution doesn't fit subbuffer size\n");
	return -EINVAL;
	}

	pcm_hw->info = MOST_PCM_INFO;
	pcm_hw->rates = SNDRV_PCM_RATE_48000;
	pcm_hw->rate_min = 48000;
	pcm_hw->rate_max = 48000;
	pcm_hw->buffer_bytes_max = cfg->num_buffers * cfg->buffer_size;
	pcm_hw->period_bytes_min = cfg->buffer_size;
	pcm_hw->period_bytes_max = cfg->buffer_size;
	pcm_hw->periods_min = 1;
	pcm_hw->periods_max = cfg->num_buffers;
	pcm_hw->channels_min = ch_num;
	pcm_hw->channels_max = ch_num;
	pcm_hw->formats = sinfo[i].formats;
	return 0;
	}

	static void release_adapter(struct sound_adapter *adpt)
	{
	struct channel channel, tmp;

	list_for_each_entry_safe(channel, tmp, &adpt->dev_list, list) {
	list_del(&channel->list);
	kfree(channel);
	}
	if (adpt->card)
	snd_card_free(adpt->card);
	list_del(&adpt->list);
	kfree(adpt);
	}

	/**
	* 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
	* @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,
	char device_name, char arg_list)
	{
	struct channel *channel;
	struct sound_adapter *adpt;
	struct snd_pcm *pcm;
	int playback_count = 0;
	int capture_count = 0;
	int ret;
	int direction;
	u16 ch_num;
	char *sample_res;
	char arg_list_cpy[STRING_SIZE];

	if (cfg->data_type != MOST_CH_SYNC) {
	pr_err("Incompatible channel type\n");
	return -EINVAL;
	}
	strscpy(arg_list_cpy, arg_list, STRING_SIZE);
	ret = split_arg_list(arg_list_cpy, &ch_num, &sample_res);
	if (ret < 0)
	return ret;

	list_for_each_entry(adpt, &adpt_list, list) {
	if (adpt->iface != iface)
	continue;
	if (adpt->registered)
	return -ENOSPC;
	adpt->pcm_dev_idx++;
	goto skip_adpt_alloc;
	}
	adpt = kzalloc(sizeof(*adpt), GFP_KERNEL);
	if (!adpt)
	return -ENOMEM;

	adpt->iface = iface;
	INIT_LIST_HEAD(&adpt->dev_list);
	iface->priv = adpt;
	list_add_tail(&adpt->list, &adpt_list);
	ret = snd_card_new(iface->driver_dev, -1, "INIC", THIS_MODULE,
	sizeof(*channel), &adpt->card);
	if (ret < 0)
	goto err_free_adpt;
	snprintf(adpt->card->driver, sizeof(adpt->card->driver),
	"%s", DRIVER_NAME);
	snprintf(adpt->card->shortname, sizeof(adpt->card->shortname),
	"Microchip INIC");
	snprintf(adpt->card->longname, sizeof(adpt->card->longname),
	"%s at %s", adpt->card->shortname, iface->description);
	skip_adpt_alloc:
	if (get_channel(iface, channel_id)) {
	pr_err("channel (%s:%d) is already linked\n",
	iface->description, channel_id);
	return -EEXIST;
	}

	if (cfg->direction == MOST_CH_TX) {
	playback_count = 1;
	direction = SNDRV_PCM_STREAM_PLAYBACK;
	} else {
	capture_count = 1;
	direction = SNDRV_PCM_STREAM_CAPTURE;
	}
	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
	if (!channel) {
	ret = -ENOMEM;
	goto err_free_adpt;
	}
	channel->card = adpt->card;
	channel->cfg = cfg;
	channel->iface = iface;
	channel->id = channel_id;
	init_waitqueue_head(&channel->playback_waitq);
	list_add_tail(&channel->list, &adpt->dev_list);

	ret = audio_set_hw_params(&channel->pcm_hardware, ch_num, sample_res,
	cfg);
	if (ret)
	goto err_free_adpt;

	ret = snd_pcm_new(adpt->card, device_name, adpt->pcm_dev_idx,
	playback_count, capture_count, &pcm);

	if (ret < 0)
	goto err_free_adpt;

	pcm->private_data = channel;
	strscpy(pcm->name, device_name, sizeof(pcm->name));
	snd_pcm_set_ops(pcm, direction, &pcm_ops);
	snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_VMALLOC, NULL, 0, 0);
	return 0;

	err_free_adpt:
	release_adapter(adpt);
	return ret;
	}

	static int audio_create_sound_card(void)
	{
	int ret;
	struct sound_adapter *adpt;

	list_for_each_entry(adpt, &adpt_list, list) {
	if (!adpt->registered)
	goto adpt_alloc;
	}
	return -ENODEV;
	adpt_alloc:
	ret = snd_card_register(adpt->card);
	if (ret < 0) {
	release_adapter(adpt);
	return ret;
	}
	adpt->registered = true;
	return 0;
	}

	/**
	* 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;
	struct sound_adapter *adpt = iface->priv;

	channel = get_channel(iface, channel_id);
	if (!channel)
	return -EINVAL;

	list_del(&channel->list);

	kfree(channel);
	if (list_empty(&adpt->dev_list))
	release_adapter(adpt);
	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)
	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)
	return -EINVAL;

	wake_up_interruptible(&channel->playback_waitq);
	return 0;
	}

	/**
	* Initialization of the struct most_component
	*/
	static struct most_component comp = {
	.mod = THIS_MODULE,
	.name = DRIVER_NAME,
	.probe_channel = audio_probe_channel,
	.disconnect_channel = audio_disconnect_channel,
	.rx_completion = audio_rx_completion,
	.tx_completion = audio_tx_completion,
	.cfg_complete = audio_create_sound_card,
	};

	static int __init audio_init(void)
	{
	int ret;

	INIT_LIST_HEAD(&adpt_list);

	ret = most_register_component(&comp);
	if (ret) {
	pr_err("Failed to register %s\n", comp.name);
	return ret;
	}
	ret = most_register_configfs_subsys(&comp);
	if (ret) {
	pr_err("Failed to register %s configfs subsys\n", comp.name);
	most_deregister_component(&comp);
	}
	return ret;
	}

	static void __exit audio_exit(void)
	{
	most_deregister_configfs_subsys(&comp);
	most_deregister_component(&comp);
	}

	module_init(audio_init);
	module_exit(audio_exit);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Christian Gromm <[email protected]>");
	MODULE_DESCRIPTION("Sound Component Module for Mostcore");