/*
 * u_audio.c -- interface to USB gadget "ALSA sound card" utilities
 *
 * Copyright (C) 2016
 * Author: Ruslan Bilovol <ruslan.bilovol@gmail.com>
 *
 * Sound card implementation was cut-and-pasted with changes
 * from f_uac2.c and has:
 *    Copyright (C) 2011
 *    Yadwinder Singh (yadi.brar01@gmail.com)
 *    Jaswinder Singh (jaswinder.singh@linaro.org)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 */

#include <linux/module.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>

#include "u_audio.h"

#define BUFF_SIZE_MAX   (PAGE_SIZE * 16)
#define PRD_SIZE_MAX    PAGE_SIZE
#define MIN_PERIODS     4

struct uac_req {
        struct uac_rtd_params *pp; /* parent param */
        struct usb_request *req;
};

/* Runtime data params for one stream */
struct uac_rtd_params {
        struct snd_uac_chip *uac; /* parent chip */
        bool ep_enabled; /* if the ep is enabled */
        /* Size of the ring buffer */
        size_t dma_bytes;
        unsigned char *dma_area;

        struct snd_pcm_substream *ss;

        /* Ring buffer */
        ssize_t hw_ptr;

        void *rbuf;

        size_t period_size;

        unsigned max_psize;     /* MaxPacketSize of endpoint */
        struct uac_req *ureq;

        spinlock_t lock;
};

struct snd_uac_chip {
        struct g_audio *audio_dev;

        struct uac_rtd_params p_prm;
        struct uac_rtd_params c_prm;

        struct snd_card *card;
        struct snd_pcm *pcm;

        /* timekeeping for the playback endpoint */
        unsigned int p_interval;
        unsigned int p_residue;

        /* pre-calculated values for playback iso completion */
        unsigned int p_pktsize;
        unsigned int p_pktsize_residue;
        unsigned int p_framesize;
};

static struct snd_pcm_hardware uac_pcm_hardware = {
        .info = SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER
                 | SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID
                 | SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME,
        .rates = SNDRV_PCM_RATE_CONTINUOUS,
        .periods_max = BUFF_SIZE_MAX / PRD_SIZE_MAX,
        .buffer_bytes_max = BUFF_SIZE_MAX,
        .period_bytes_max = PRD_SIZE_MAX,
        .periods_min = MIN_PERIODS,
};

static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
{
        unsigned pending;
        unsigned long flags;
        unsigned int hw_ptr;
        bool update_alsa = false;
        int status = req->status;
        struct uac_req *ur = req->context;
        struct snd_pcm_substream *substream;
        struct uac_rtd_params *prm = ur->pp;
        struct snd_uac_chip *uac = prm->uac;

        /* i/f shutting down */
        if (!prm->ep_enabled || req->status == -ESHUTDOWN)
                return;

        /*
         * We can't really do much about bad xfers.
         * Afterall, the ISOCH xfers could fail legitimately.
         */
        if (status)
                pr_debug("%s: iso_complete status(%d) %d/%d\n",
                        __func__, status, req->actual, req->length);

        substream = prm->ss;

        /* Do nothing if ALSA isn't active */
        if (!substream)
                goto exit;

        spin_lock_irqsave(&prm->lock, flags);

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                /*
                 * For each IN packet, take the quotient of the current data
                 * rate and the endpoint's interval as the base packet size.
                 * If there is a residue from this division, add it to the
                 * residue accumulator.
                 */
                req->length = uac->p_pktsize;
                uac->p_residue += uac->p_pktsize_residue;

                /*
                 * Whenever there are more bytes in the accumulator than we
                 * need to add one more sample frame, increase this packet's
                 * size and decrease the accumulator.
                 */
                if (uac->p_residue / uac->p_interval >= uac->p_framesize) {
                        req->length += uac->p_framesize;
                        uac->p_residue -= uac->p_framesize *
                                           uac->p_interval;
                }

                req->actual = req->length;
        }

        pending = prm->hw_ptr % prm->period_size;
        pending += req->actual;
        if (pending >= prm->period_size)
                update_alsa = true;

        hw_ptr = prm->hw_ptr;
        prm->hw_ptr = (prm->hw_ptr + req->actual) % prm->dma_bytes;

        spin_unlock_irqrestore(&prm->lock, flags);

        /* Pack USB load in ALSA ring buffer */
        pending = prm->dma_bytes - hw_ptr;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                if (unlikely(pending < req->actual)) {
                        memcpy(req->buf, prm->dma_area + hw_ptr, pending);
                        memcpy(req->buf + pending, prm->dma_area,
                               req->actual - pending);
                } else {
                        memcpy(req->buf, prm->dma_area + hw_ptr, req->actual);
                }
        } else {
                if (unlikely(pending < req->actual)) {
                        memcpy(prm->dma_area + hw_ptr, req->buf, pending);
                        memcpy(prm->dma_area, req->buf + pending,
                               req->actual - pending);
                } else {
                        memcpy(prm->dma_area + hw_ptr, req->buf, req->actual);
                }
        }

exit:
        if (usb_ep_queue(ep, req, GFP_ATOMIC))
                dev_err(uac->card->dev, "%d Error!\n", __LINE__);

        if (update_alsa)
                snd_pcm_period_elapsed(substream);
}

static int uac_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
{
        struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
        struct uac_rtd_params *prm;
        struct g_audio *audio_dev;
        struct uac_params *params;
        unsigned long flags;
        int err = 0;

        audio_dev = uac->audio_dev;
        params = &audio_dev->params;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                prm = &uac->p_prm;
        else
                prm = &uac->c_prm;

        spin_lock_irqsave(&prm->lock, flags);

        /* Reset */
        prm->hw_ptr = 0;

        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
        case SNDRV_PCM_TRIGGER_RESUME:
                prm->ss = substream;
                break;
        case SNDRV_PCM_TRIGGER_STOP:
        case SNDRV_PCM_TRIGGER_SUSPEND:
                prm->ss = NULL;
                break;
        default:
                err = -EINVAL;
        }

        spin_unlock_irqrestore(&prm->lock, flags);

        /* Clear buffer after Play stops */
        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK && !prm->ss)
                memset(prm->rbuf, 0, prm->max_psize * params->req_number);

        return err;
}

static snd_pcm_uframes_t uac_pcm_pointer(struct snd_pcm_substream *substream)
{
        struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
        struct uac_rtd_params *prm;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                prm = &uac->p_prm;
        else
                prm = &uac->c_prm;

        return bytes_to_frames(substream->runtime, prm->hw_ptr);
}

static int uac_pcm_hw_params(struct snd_pcm_substream *substream,
                               struct snd_pcm_hw_params *hw_params)
{
        struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
        struct uac_rtd_params *prm;
        int err;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                prm = &uac->p_prm;
        else
                prm = &uac->c_prm;

        err = snd_pcm_lib_malloc_pages(substream,
                                        params_buffer_bytes(hw_params));
        if (err >= 0) {
                prm->dma_bytes = substream->runtime->dma_bytes;
                prm->dma_area = substream->runtime->dma_area;
                prm->period_size = params_period_bytes(hw_params);
        }

        return err;
}

static int uac_pcm_hw_free(struct snd_pcm_substream *substream)
{
        struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
        struct uac_rtd_params *prm;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                prm = &uac->p_prm;
        else
                prm = &uac->c_prm;

        prm->dma_area = NULL;
        prm->dma_bytes = 0;
        prm->period_size = 0;

        return snd_pcm_lib_free_pages(substream);
}

static int uac_pcm_open(struct snd_pcm_substream *substream)
{
        struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct g_audio *audio_dev;
        struct uac_params *params;
        int p_ssize, c_ssize;
        int p_srate, c_srate;
        int p_chmask, c_chmask;

        audio_dev = uac->audio_dev;
        params = &audio_dev->params;
        p_ssize = params->p_ssize;
        c_ssize = params->c_ssize;
        p_srate = params->p_srate;
        c_srate = params->c_srate;
        p_chmask = params->p_chmask;
        c_chmask = params->c_chmask;
        uac->p_residue = 0;

        runtime->hw = uac_pcm_hardware;

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
                spin_lock_init(&uac->p_prm.lock);
                runtime->hw.rate_min = p_srate;
                switch (p_ssize) {
                case 3:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S24_3LE;
                        break;
                case 4:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S32_LE;
                        break;
                default:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S16_LE;
                        break;
                }
                runtime->hw.channels_min = num_channels(p_chmask);
                runtime->hw.period_bytes_min = 2 * uac->p_prm.max_psize
                                                / runtime->hw.periods_min;
        } else {
                spin_lock_init(&uac->c_prm.lock);
                runtime->hw.rate_min = c_srate;
                switch (c_ssize) {
                case 3:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S24_3LE;
                        break;
                case 4:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S32_LE;
                        break;
                default:
                        runtime->hw.formats = SNDRV_PCM_FMTBIT_S16_LE;
                        break;
                }
                runtime->hw.channels_min = num_channels(c_chmask);
                runtime->hw.period_bytes_min = 2 * uac->c_prm.max_psize
                                                / runtime->hw.periods_min;
        }

        runtime->hw.rate_max = runtime->hw.rate_min;
        runtime->hw.channels_max = runtime->hw.channels_min;

        snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);

        return 0;
}

/* ALSA cries without these function pointers */
static int uac_pcm_null(struct snd_pcm_substream *substream)
{
        return 0;
}

static struct snd_pcm_ops uac_pcm_ops = {
        .open = uac_pcm_open,
        .close = uac_pcm_null,
        .ioctl = snd_pcm_lib_ioctl,
        .hw_params = uac_pcm_hw_params,
        .hw_free = uac_pcm_hw_free,
        .trigger = uac_pcm_trigger,
        .pointer = uac_pcm_pointer,
        .prepare = uac_pcm_null,
};

static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep *ep)
{
        struct snd_uac_chip *uac = prm->uac;
        struct g_audio *audio_dev;
        struct uac_params *params;
        int i;

        if (!prm->ep_enabled)
                return;

        prm->ep_enabled = false;

        audio_dev = uac->audio_dev;
        params = &audio_dev->params;

        for (i = 0; i < params->req_number; i++) {
                if (prm->ureq[i].req) {
                        usb_ep_dequeue(ep, prm->ureq[i].req);
                        usb_ep_free_request(ep, prm->ureq[i].req);
                        prm->ureq[i].req = NULL;
                }
        }

        if (usb_ep_disable(ep))
                dev_err(uac->card->dev, "%s:%d Error!\n", __func__, __LINE__);
}


int u_audio_start_capture(struct g_audio *audio_dev)
{
        struct snd_uac_chip *uac = audio_dev->uac;
        struct usb_gadget *gadget = audio_dev->gadget;
        struct device *dev = &gadget->dev;
        struct usb_request *req;
        struct usb_ep *ep;
        struct uac_rtd_params *prm;
        struct uac_params *params = &audio_dev->params;
        int req_len, i;

        ep = audio_dev->out_ep;
        prm = &uac->c_prm;
        config_ep_by_speed(gadget, &audio_dev->func, ep);
        req_len = prm->max_psize;

        prm->ep_enabled = true;
        usb_ep_enable(ep);

        for (i = 0; i < params->req_number; i++) {
                if (!prm->ureq[i].req) {
                        req = usb_ep_alloc_request(ep, GFP_ATOMIC);
                        if (req == NULL)
                                return -ENOMEM;

                        prm->ureq[i].req = req;
                        prm->ureq[i].pp = prm;

                        req->zero = 0;
                        req->context = &prm->ureq[i];
                        req->length = req_len;
                        req->complete = u_audio_iso_complete;
                        req->buf = prm->rbuf + i * prm->max_psize;
                }

                if (usb_ep_queue(ep, prm->ureq[i].req, GFP_ATOMIC))
                        dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
        }

        return 0;
}
EXPORT_SYMBOL_GPL(u_audio_start_capture);

void u_audio_stop_capture(struct g_audio *audio_dev)
{
        struct snd_uac_chip *uac = audio_dev->uac;

        free_ep(&uac->c_prm, audio_dev->out_ep);
}
EXPORT_SYMBOL_GPL(u_audio_stop_capture);

int u_audio_start_playback(struct g_audio *audio_dev)
{
        struct snd_uac_chip *uac = audio_dev->uac;
        struct usb_gadget *gadget = audio_dev->gadget;
        struct device *dev = &gadget->dev;
        struct usb_request *req;
        struct usb_ep *ep;
        struct uac_rtd_params *prm;
        struct uac_params *params = &audio_dev->params;
        unsigned int factor, rate;
        const struct usb_endpoint_descriptor *ep_desc;
        int req_len, i;

        ep = audio_dev->in_ep;
        prm = &uac->p_prm;
        config_ep_by_speed(gadget, &audio_dev->func, ep);

        ep_desc = ep->desc;

        /* pre-calculate the playback endpoint's interval */
        if (gadget->speed == USB_SPEED_FULL)
                factor = 1000;
        else
                factor = 8000;

        /* pre-compute some values for iso_complete() */
        uac->p_framesize = params->p_ssize *
                            num_channels(params->p_chmask);
        rate = params->p_srate * uac->p_framesize;
        uac->p_interval = factor / (1 << (ep_desc->bInterval - 1));
        uac->p_pktsize = min_t(unsigned int, rate / uac->p_interval,
                                prm->max_psize);

        if (uac->p_pktsize < prm->max_psize)
                uac->p_pktsize_residue = rate % uac->p_interval;
        else
                uac->p_pktsize_residue = 0;

        req_len = uac->p_pktsize;
        uac->p_residue = 0;

        prm->ep_enabled = true;
        usb_ep_enable(ep);

        for (i = 0; i < params->req_number; i++) {
                if (!prm->ureq[i].req) {
                        req = usb_ep_alloc_request(ep, GFP_ATOMIC);
                        if (req == NULL)
                                return -ENOMEM;

                        prm->ureq[i].req = req;
                        prm->ureq[i].pp = prm;

                        req->zero = 0;
                        req->context = &prm->ureq[i];
                        req->length = req_len;
                        req->complete = u_audio_iso_complete;
                        req->buf = prm->rbuf + i * prm->max_psize;
                }

                if (usb_ep_queue(ep, prm->ureq[i].req, GFP_ATOMIC))
                        dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
        }

        return 0;
}
EXPORT_SYMBOL_GPL(u_audio_start_playback);

void u_audio_stop_playback(struct g_audio *audio_dev)
{
        struct snd_uac_chip *uac = audio_dev->uac;

        free_ep(&uac->p_prm, audio_dev->in_ep);
}
EXPORT_SYMBOL_GPL(u_audio_stop_playback);

int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
                                        const char *card_name)
{
        struct snd_uac_chip *uac;
        struct snd_card *card;
        struct snd_pcm *pcm;
        struct uac_params *params;
        int p_chmask, c_chmask;
        int err;

        if (!g_audio)
                return -EINVAL;

        uac = kzalloc(sizeof(*uac), GFP_KERNEL);
        if (!uac)
                return -ENOMEM;
        g_audio->uac = uac;
        uac->audio_dev = g_audio;

        params = &g_audio->params;
        p_chmask = params->p_chmask;
        c_chmask = params->c_chmask;

        if (c_chmask) {
                struct uac_rtd_params *prm = &uac->c_prm;

                uac->c_prm.uac = uac;
                prm->max_psize = g_audio->out_ep_maxpsize;

                prm->ureq = kcalloc(params->req_number, sizeof(struct uac_req),
                                GFP_KERNEL);
                if (!prm->ureq) {
                        err = -ENOMEM;
                        goto fail;
                }

                prm->rbuf = kcalloc(params->req_number, prm->max_psize,
                                GFP_KERNEL);
                if (!prm->rbuf) {
                        prm->max_psize = 0;
                        err = -ENOMEM;
                        goto fail;
                }
        }

        if (p_chmask) {
                struct uac_rtd_params *prm = &uac->p_prm;

                uac->p_prm.uac = uac;
                prm->max_psize = g_audio->in_ep_maxpsize;

                prm->ureq = kcalloc(params->req_number, sizeof(struct uac_req),
                                GFP_KERNEL);
                if (!prm->ureq) {
                        err = -ENOMEM;
                        goto fail;
                }

                prm->rbuf = kcalloc(params->req_number, prm->max_psize,
                                GFP_KERNEL);
                if (!prm->rbuf) {
                        prm->max_psize = 0;
                        err = -ENOMEM;
                        goto fail;
                }
        }

        /* Choose any slot, with no id */
        err = snd_card_new(&g_audio->gadget->dev,
                        -1, NULL, THIS_MODULE, 0, &card);
        if (err < 0)
                goto fail;

        uac->card = card;

        /*
         * Create first PCM device
         * Create a substream only for non-zero channel streams
         */
        err = snd_pcm_new(uac->card, pcm_name, 0,
                               p_chmask ? 1 : 0, c_chmask ? 1 : 0, &pcm);
        if (err < 0)
                goto snd_fail;

        strcpy(pcm->name, pcm_name);
        pcm->private_data = uac;
        uac->pcm = pcm;

        snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &uac_pcm_ops);
        snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &uac_pcm_ops);

        strcpy(card->driver, card_name);
        strcpy(card->shortname, card_name);
        sprintf(card->longname, "%s %i", card_name, card->dev->id);

        snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
                snd_dma_continuous_data(GFP_KERNEL), 0, BUFF_SIZE_MAX);

        err = snd_card_register(card);

        if (!err)
                return 0;

snd_fail:
        snd_card_free(card);
fail:
        kfree(uac->p_prm.ureq);
        kfree(uac->c_prm.ureq);
        kfree(uac->p_prm.rbuf);
        kfree(uac->c_prm.rbuf);
        kfree(uac);

        return err;
}
EXPORT_SYMBOL_GPL(g_audio_setup);

void g_audio_cleanup(struct g_audio *g_audio)
{
        struct snd_uac_chip *uac;
        struct snd_card *card;

        if (!g_audio || !g_audio->uac)
                return;

        uac = g_audio->uac;
        card = uac->card;
        if (card)
                snd_card_free(card);

        kfree(uac->p_prm.ureq);
        kfree(uac->c_prm.ureq);
        kfree(uac->p_prm.rbuf);
        kfree(uac->c_prm.rbuf);
        kfree(uac);
}
EXPORT_SYMBOL_GPL(g_audio_cleanup);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("USB gadget \"ALSA sound card\" utilities");
MODULE_AUTHOR("Ruslan Bilovol");