Re: [PATCH v4 2/3] usb: gadget: f_uac2: split out audio core

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On Thu, May 18, 2017 at 4:07 AM, Ruslan Bilovol
<ruslan.bilovol@xxxxxxxxx> wrote:
> Abstract the peripheral side ALSA sound card code from
> the f_uac2 function into a component that can be called
> by various functions, so the various flavors can be split
> apart and selectively reused.
>
> Visible changes:
>  - add uac_params structure to pass audio paramteres for
>    g_audio_setup
>  - make ALSA sound card's name configurable
>  - add [in/out]_ep_maxpsize
>  - allocate snd_uac_chip structure during g_audio_setup
>  - add u_audio_[start/stop]_[capture/playback] functions
>
> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx>
> ---
>  drivers/usb/gadget/Kconfig            |   4 +
>  drivers/usb/gadget/function/Makefile  |   1 +
>  drivers/usb/gadget/function/f_uac2.c  | 721 ++++------------------------------
>  drivers/usb/gadget/function/u_audio.c | 661 +++++++++++++++++++++++++++++++
>  drivers/usb/gadget/function/u_audio.h |  95 +++++
>  drivers/usb/gadget/legacy/Kconfig     |   1 +
>  6 files changed, 846 insertions(+), 637 deletions(-)
>  create mode 100644 drivers/usb/gadget/function/u_audio.c
>  create mode 100644 drivers/usb/gadget/function/u_audio.h
>
> diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
> index c164d6b..2ba0ace 100644
> --- a/drivers/usb/gadget/Kconfig
> +++ b/drivers/usb/gadget/Kconfig
> @@ -158,6 +158,9 @@ config USB_U_SERIAL
>  config USB_U_ETHER
>         tristate
>
> +config USB_U_AUDIO
> +       tristate
> +
>  config USB_F_SERIAL
>         tristate
>
> @@ -381,6 +384,7 @@ config USB_CONFIGFS_F_UAC2
>         depends on SND
>         select USB_LIBCOMPOSITE
>         select SND_PCM
> +       select USB_U_AUDIO
>         select USB_F_UAC2
>         help
>           This Audio function is compatible with USB Audio Class
> diff --git a/drivers/usb/gadget/function/Makefile b/drivers/usb/gadget/function/Makefile
> index cb8c225..b29f2ae 100644
> --- a/drivers/usb/gadget/function/Makefile
> +++ b/drivers/usb/gadget/function/Makefile
> @@ -32,6 +32,7 @@ usb_f_mass_storage-y          := f_mass_storage.o storage_common.o
>  obj-$(CONFIG_USB_F_MASS_STORAGE)+= usb_f_mass_storage.o
>  usb_f_fs-y                     := f_fs.o
>  obj-$(CONFIG_USB_F_FS)         += usb_f_fs.o
> +obj-$(CONFIG_USB_U_AUDIO)      += u_audio.o
>  usb_f_uac1-y                   := f_uac1.o u_uac1.o
>  obj-$(CONFIG_USB_F_UAC1)       += usb_f_uac1.o
>  usb_f_uac2-y                   := f_uac2.o
> diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
> index d4565b5..059a14a 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -15,10 +15,7 @@
>  #include <linux/usb/audio-v2.h>
>  #include <linux/module.h>
>
> -#include <sound/core.h>
> -#include <sound/pcm.h>
> -#include <sound/pcm_params.h>
> -
> +#include "u_audio.h"
>  #include "u_uac2.h"
>
>  /*
> @@ -50,455 +47,23 @@
>  #define UNFLW_CTRL     8
>  #define OVFLW_CTRL     10
>
> -struct uac2_req {
> -       struct uac2_rtd_params *pp; /* parent param */
> -       struct usb_request *req;
> -};
> -
> -struct uac2_rtd_params {
> -       struct snd_uac2_chip *uac2; /* 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;
> -       struct uac2_req *ureq;
> -
> -       spinlock_t lock;
> -};
> -
> -struct snd_uac2_chip {
> -       struct uac2_rtd_params p_prm;
> -       struct uac2_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;
> +struct f_uac2 {
> +       struct g_audio g_audio;
> +       u8 ac_intf, as_in_intf, as_out_intf;
> +       u8 ac_alt, as_in_alt, as_out_alt;       /* needed for get_alt() */
>  };
>
> -#define BUFF_SIZE_MAX  (PAGE_SIZE * 16)
> -#define PRD_SIZE_MAX   PAGE_SIZE
> -#define MIN_PERIODS    4
> -
> -static struct snd_pcm_hardware uac2_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,
> -};
> -
> -struct audio_dev {
> -       u8 ac_intf, ac_alt;
> -       u8 as_out_intf, as_out_alt;
> -       u8 as_in_intf, as_in_alt;
> -
> -       struct usb_ep *in_ep, *out_ep;
> -       struct usb_function func;
> -       struct usb_gadget *gadget;
> -
> -       /* The ALSA Sound Card it represents on the USB-Client side */
> -       struct snd_uac2_chip uac2;
> -};
> -
> -static inline
> -struct audio_dev *func_to_agdev(struct usb_function *f)
> +static inline struct f_uac2 *func_to_uac2(struct usb_function *f)
>  {
> -       return container_of(f, struct audio_dev, func);
> +       return container_of(f, struct f_uac2, g_audio.func);
>  }
>
>  static inline
> -struct audio_dev *uac2_to_agdev(struct snd_uac2_chip *u)
> -{
> -       return container_of(u, struct audio_dev, uac2);
> -}
> -
> -static inline
> -struct f_uac2_opts *agdev_to_uac2_opts(struct audio_dev *agdev)
> +struct f_uac2_opts *g_audio_to_uac2_opts(struct g_audio *agdev)
>  {
>         return container_of(agdev->func.fi, struct f_uac2_opts, func_inst);
>  }
>
> -static inline
> -uint num_channels(uint chanmask)
> -{
> -       uint num = 0;
> -
> -       while (chanmask) {
> -               num += (chanmask & 1);
> -               chanmask >>= 1;
> -       }
> -
> -       return num;
> -}
> -
> -static void
> -agdev_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 uac2_req *ur = req->context;
> -       struct snd_pcm_substream *substream;
> -       struct uac2_rtd_params *prm = ur->pp;
> -       struct snd_uac2_chip *uac2 = prm->uac2;
> -
> -       /* 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 = uac2->p_pktsize;
> -               uac2->p_residue += uac2->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 (uac2->p_residue / uac2->p_interval >= uac2->p_framesize) {
> -                       req->length += uac2->p_framesize;
> -                       uac2->p_residue -= uac2->p_framesize *
> -                                          uac2->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(uac2->card->dev, "%d Error!\n", __LINE__);
> -
> -       if (update_alsa)
> -               snd_pcm_period_elapsed(substream);
> -
> -       return;
> -}
> -
> -static int
> -uac2_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
> -{
> -       struct snd_uac2_chip *uac2 = snd_pcm_substream_chip(substream);
> -       struct audio_dev *agdev = uac2_to_agdev(uac2);
> -       struct f_uac2_opts *uac2_opts = agdev_to_uac2_opts(agdev);
> -       struct uac2_rtd_params *prm;
> -       unsigned long flags;
> -       int err = 0;
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> -               prm = &uac2->p_prm;
> -       else
> -               prm = &uac2->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 * uac2_opts->req_number);
> -
> -       return err;
> -}
> -
> -static snd_pcm_uframes_t uac2_pcm_pointer(struct snd_pcm_substream *substream)
> -{
> -       struct snd_uac2_chip *uac2 = snd_pcm_substream_chip(substream);
> -       struct uac2_rtd_params *prm;
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> -               prm = &uac2->p_prm;
> -       else
> -               prm = &uac2->c_prm;
> -
> -       return bytes_to_frames(substream->runtime, prm->hw_ptr);
> -}
> -
> -static int uac2_pcm_hw_params(struct snd_pcm_substream *substream,
> -                              struct snd_pcm_hw_params *hw_params)
> -{
> -       struct snd_uac2_chip *uac2 = snd_pcm_substream_chip(substream);
> -       struct uac2_rtd_params *prm;
> -       int err;
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> -               prm = &uac2->p_prm;
> -       else
> -               prm = &uac2->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 uac2_pcm_hw_free(struct snd_pcm_substream *substream)
> -{
> -       struct snd_uac2_chip *uac2 = snd_pcm_substream_chip(substream);
> -       struct uac2_rtd_params *prm;
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
> -               prm = &uac2->p_prm;
> -       else
> -               prm = &uac2->c_prm;
> -
> -       prm->dma_area = NULL;
> -       prm->dma_bytes = 0;
> -       prm->period_size = 0;
> -
> -       return snd_pcm_lib_free_pages(substream);
> -}
> -
> -static int uac2_pcm_open(struct snd_pcm_substream *substream)
> -{
> -       struct snd_uac2_chip *uac2 = snd_pcm_substream_chip(substream);
> -       struct snd_pcm_runtime *runtime = substream->runtime;
> -       struct audio_dev *audio_dev;
> -       struct f_uac2_opts *opts;
> -       int p_ssize, c_ssize;
> -       int p_srate, c_srate;
> -       int p_chmask, c_chmask;
> -
> -       audio_dev = uac2_to_agdev(uac2);
> -       opts = container_of(audio_dev->func.fi, struct f_uac2_opts, func_inst);
> -       p_ssize = opts->p_ssize;
> -       c_ssize = opts->c_ssize;
> -       p_srate = opts->p_srate;
> -       c_srate = opts->c_srate;
> -       p_chmask = opts->p_chmask;
> -       c_chmask = opts->c_chmask;
> -       uac2->p_residue = 0;
> -
> -       runtime->hw = uac2_pcm_hardware;
> -
> -       if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
> -               spin_lock_init(&uac2->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 * uac2->p_prm.max_psize
> -                                               / runtime->hw.periods_min;
> -       } else {
> -               spin_lock_init(&uac2->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 * uac2->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 uac2_pcm_null(struct snd_pcm_substream *substream)
> -{
> -       return 0;
> -}
> -
> -static struct snd_pcm_ops uac2_pcm_ops = {
> -       .open = uac2_pcm_open,
> -       .close = uac2_pcm_null,
> -       .ioctl = snd_pcm_lib_ioctl,
> -       .hw_params = uac2_pcm_hw_params,
> -       .hw_free = uac2_pcm_hw_free,
> -       .trigger = uac2_pcm_trigger,
> -       .pointer = uac2_pcm_pointer,
> -       .prepare = uac2_pcm_null,
> -};
> -
> -static int snd_uac2_probe(struct audio_dev *audio_dev)
> -{
> -       struct snd_uac2_chip *uac2 = &audio_dev->uac2;
> -       struct snd_card *card;
> -       struct snd_pcm *pcm;
> -       struct f_uac2_opts *opts;
> -       int err;
> -       int p_chmask, c_chmask;
> -
> -       opts = container_of(audio_dev->func.fi, struct f_uac2_opts, func_inst);
> -       p_chmask = opts->p_chmask;
> -       c_chmask = opts->c_chmask;
> -
> -       /* Choose any slot, with no id */
> -       err = snd_card_new(&audio_dev->gadget->dev,
> -                       -1, NULL, THIS_MODULE, 0, &card);
> -       if (err < 0)
> -               return err;
> -
> -       uac2->card = card;
> -
> -       /*
> -        * Create first PCM device
> -        * Create a substream only for non-zero channel streams
> -        */
> -       err = snd_pcm_new(uac2->card, "UAC2 PCM", 0,
> -                              p_chmask ? 1 : 0, c_chmask ? 1 : 0, &pcm);
> -       if (err < 0)
> -               goto snd_fail;
> -
> -       strcpy(pcm->name, "UAC2 PCM");
> -       pcm->private_data = uac2;
> -
> -       uac2->pcm = pcm;
> -
> -       snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &uac2_pcm_ops);
> -       snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &uac2_pcm_ops);
> -
> -       strcpy(card->driver, "UAC2_Gadget");
> -       strcpy(card->shortname, "UAC2_Gadget");
> -       sprintf(card->longname, "UAC2_Gadget %i", 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);
> -
> -       uac2->pcm = NULL;
> -       uac2->card = NULL;
> -
> -       return err;
> -}
> -
> -static int snd_uac2_remove(struct audio_dev *audio_dev)
> -{
> -       struct snd_card *card = audio_dev->uac2.card;
> -
> -       if (card)
> -               return snd_card_free(card);
> -
> -       return 0;
> -}
> -
> -
>  /* --------- USB Function Interface ------------- */
>
>  enum {
> @@ -886,32 +451,6 @@ struct cntrl_range_lay3 {
>         __u32   dRES;
>  } __packed;
>
> -static inline void
> -free_ep(struct uac2_rtd_params *prm, struct usb_ep *ep)
> -{
> -       struct snd_uac2_chip *uac2 = prm->uac2;
> -       struct audio_dev *agdev = uac2_to_agdev(uac2);
> -       struct f_uac2_opts *uac2_opts = agdev_to_uac2_opts(agdev);
> -       int i;
> -
> -       if (!prm->ep_enabled)
> -               return;
> -
> -       prm->ep_enabled = false;
> -
> -       for (i = 0; i < uac2_opts->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(uac2->card->dev,
> -                       "%s:%d Error!\n", __func__, __LINE__);
> -}
> -
>  static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>         struct usb_endpoint_descriptor *ep_desc,
>         unsigned int factor, bool is_playback)
> @@ -938,12 +477,11 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  static int
>  afunc_bind(struct usb_configuration *cfg, struct usb_function *fn)
>  {
> -       struct audio_dev *agdev = func_to_agdev(fn);
> -       struct snd_uac2_chip *uac2 = &agdev->uac2;
> +       struct f_uac2 *uac2 = func_to_uac2(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
>         struct usb_composite_dev *cdev = cfg->cdev;
>         struct usb_gadget *gadget = cdev->gadget;
>         struct device *dev = &gadget->dev;
> -       struct uac2_rtd_params *prm;
>         struct f_uac2_opts *uac2_opts;
>         struct usb_string *us;
>         int ret;
> @@ -990,8 +528,8 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>                 return ret;
>         }
>         std_ac_if_desc.bInterfaceNumber = ret;
> -       agdev->ac_intf = ret;
> -       agdev->ac_alt = 0;
> +       uac2->ac_intf = ret;
> +       uac2->ac_alt = 0;
>
>         ret = usb_interface_id(cfg, fn);
>         if (ret < 0) {
> @@ -1000,8 +538,8 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>         }
>         std_as_out_if0_desc.bInterfaceNumber = ret;
>         std_as_out_if1_desc.bInterfaceNumber = ret;
> -       agdev->as_out_intf = ret;
> -       agdev->as_out_alt = 0;
> +       uac2->as_out_intf = ret;
> +       uac2->as_out_alt = 0;
>
>         ret = usb_interface_id(cfg, fn);
>         if (ret < 0) {
> @@ -1010,8 +548,8 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>         }
>         std_as_in_if0_desc.bInterfaceNumber = ret;
>         std_as_in_if1_desc.bInterfaceNumber = ret;
> -       agdev->as_in_intf = ret;
> -       agdev->as_in_alt = 0;
> +       uac2->as_in_intf = ret;
> +       uac2->as_in_alt = 0;
>
>         agdev->out_ep = usb_ep_autoconfig(gadget, &fs_epout_desc);
>         if (!agdev->out_ep) {
> @@ -1025,15 +563,17 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>                 return ret;
>         }
>
> -       uac2->p_prm.uac2 = uac2;
> -       uac2->c_prm.uac2 = uac2;
> -
>         /* Calculate wMaxPacketSize according to audio bandwidth */
>         set_ep_max_packet_size(uac2_opts, &fs_epin_desc, 1000, true);
>         set_ep_max_packet_size(uac2_opts, &fs_epout_desc, 1000, false);
>         set_ep_max_packet_size(uac2_opts, &hs_epin_desc, 8000, true);
>         set_ep_max_packet_size(uac2_opts, &hs_epout_desc, 8000, false);
>
> +       agdev->in_ep_maxpsize = max(fs_epin_desc.wMaxPacketSize,
> +                                       hs_epin_desc.wMaxPacketSize);
> +       agdev->out_ep_maxpsize = max(fs_epout_desc.wMaxPacketSize,
> +                                       hs_epout_desc.wMaxPacketSize);
> +
>         hs_epout_desc.bEndpointAddress = fs_epout_desc.bEndpointAddress;
>         hs_epin_desc.bEndpointAddress = fs_epin_desc.bEndpointAddress;
>
> @@ -1044,46 +584,18 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>
>         agdev->gadget = gadget;
>
> -       prm = &agdev->uac2.c_prm;
> -       prm->max_psize = hs_epout_desc.wMaxPacketSize;
> -       prm->ureq = kcalloc(uac2_opts->req_number, sizeof(struct uac2_req),
> -                       GFP_KERNEL);
> -       if (!prm->ureq) {
> -               ret = -ENOMEM;
> -               goto err_free_descs;
> -       }
> -       prm->rbuf = kcalloc(uac2_opts->req_number, prm->max_psize, GFP_KERNEL);
> -       if (!prm->rbuf) {
> -               prm->max_psize = 0;
> -               ret = -ENOMEM;
> -               goto err_free_descs;
> -       }
> -
> -       prm = &agdev->uac2.p_prm;
> -       prm->max_psize = hs_epin_desc.wMaxPacketSize;
> -       prm->ureq = kcalloc(uac2_opts->req_number, sizeof(struct uac2_req),
> -                       GFP_KERNEL);
> -       if (!prm->ureq) {
> -               ret = -ENOMEM;
> -               goto err_free_descs;
> -       }
> -       prm->rbuf = kcalloc(uac2_opts->req_number, prm->max_psize, GFP_KERNEL);
> -       if (!prm->rbuf) {
> -               prm->max_psize = 0;
> -               ret = -ENOMEM;
> -               goto err_no_memory;
> -       }
> -
> -       ret = snd_uac2_probe(agdev);
> +       agdev->params.p_chmask = uac2_opts->p_chmask;
> +       agdev->params.p_srate = uac2_opts->p_srate;
> +       agdev->params.p_ssize = uac2_opts->p_ssize;
> +       agdev->params.c_chmask = uac2_opts->c_chmask;
> +       agdev->params.c_srate = uac2_opts->c_srate;
> +       agdev->params.c_ssize = uac2_opts->c_ssize;
> +       agdev->params.req_number = uac2_opts->req_number;
> +       ret = g_audio_setup(agdev, "UAC2 PCM", "UAC2_Gadget");
>         if (ret)
> -               goto err_no_memory;
> +               goto err_free_descs;
>         return 0;
>
> -err_no_memory:
> -       kfree(agdev->uac2.p_prm.ureq);
> -       kfree(agdev->uac2.c_prm.ureq);
> -       kfree(agdev->uac2.p_prm.rbuf);
> -       kfree(agdev->uac2.c_prm.rbuf);
>  err_free_descs:
>         usb_free_all_descriptors(fn);
>         agdev->gadget = NULL;
> @@ -1094,15 +606,10 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
>  {
>         struct usb_composite_dev *cdev = fn->config->cdev;
> -       struct audio_dev *agdev = func_to_agdev(fn);
> -       struct f_uac2_opts *opts = agdev_to_uac2_opts(agdev);
> -       struct snd_uac2_chip *uac2 = &agdev->uac2;
> +       struct f_uac2 *uac2 = func_to_uac2(fn);
>         struct usb_gadget *gadget = cdev->gadget;
>         struct device *dev = &gadget->dev;
> -       struct usb_request *req;
> -       struct usb_ep *ep;
> -       struct uac2_rtd_params *prm;
> -       int req_len, i;
> +       int ret = 0;
>
>         /* No i/f has more than 2 alt settings */
>         if (alt > 1) {
> @@ -1110,7 +617,7 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>                 return -EINVAL;
>         }
>
> -       if (intf == agdev->ac_intf) {
> +       if (intf == uac2->ac_intf) {
>                 /* Control I/f has only 1 AltSetting - 0 */
>                 if (alt) {
>                         dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
> @@ -1119,92 +626,40 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>                 return 0;
>         }
>
> -       if (intf == agdev->as_out_intf) {
> -               ep = agdev->out_ep;
> -               prm = &uac2->c_prm;
> -               config_ep_by_speed(gadget, fn, ep);
> -               agdev->as_out_alt = alt;
> -               req_len = prm->max_psize;
> -       } else if (intf == agdev->as_in_intf) {
> -               unsigned int factor, rate;
> -               struct usb_endpoint_descriptor *ep_desc;
> -
> -               ep = agdev->in_ep;
> -               prm = &uac2->p_prm;
> -               config_ep_by_speed(gadget, fn, ep);
> -               agdev->as_in_alt = alt;
> -
> -               /* pre-calculate the playback endpoint's interval */
> -               if (gadget->speed == USB_SPEED_FULL) {
> -                       ep_desc = &fs_epin_desc;
> -                       factor = 1000;
> -               } else {
> -                       ep_desc = &hs_epin_desc;
> -                       factor = 8000;
> -               }
> -
> -               /* pre-compute some values for iso_complete() */
> -               uac2->p_framesize = opts->p_ssize *
> -                                   num_channels(opts->p_chmask);
> -               rate = opts->p_srate * uac2->p_framesize;
> -               uac2->p_interval = factor / (1 << (ep_desc->bInterval - 1));
> -               uac2->p_pktsize = min_t(unsigned int, rate / uac2->p_interval,
> -                                       prm->max_psize);
> +       if (intf == uac2->as_out_intf) {
> +               uac2->as_out_alt = alt;
>
> -               if (uac2->p_pktsize < prm->max_psize)
> -                       uac2->p_pktsize_residue = rate % uac2->p_interval;
> +               if (alt)
> +                       ret = u_audio_start_capture(&uac2->g_audio);
>                 else
> -                       uac2->p_pktsize_residue = 0;
> +                       u_audio_stop_capture(&uac2->g_audio);
> +       } else if (intf == uac2->as_in_intf) {
> +               uac2->as_in_alt = alt;
>
> -               req_len = uac2->p_pktsize;
> -               uac2->p_residue = 0;
> +               if (alt)
> +                       ret = u_audio_start_playback(&uac2->g_audio);
> +               else
> +                       u_audio_stop_playback(&uac2->g_audio);
>         } else {
>                 dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
>                 return -EINVAL;
>         }
>
> -       if (alt == 0) {
> -               free_ep(prm, ep);
> -               return 0;
> -       }
> -
> -       prm->ep_enabled = true;
> -       usb_ep_enable(ep);
> -
> -       for (i = 0; i < opts->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 = agdev_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;
> +       return ret;
>  }
>
>  static int
>  afunc_get_alt(struct usb_function *fn, unsigned intf)
>  {
> -       struct audio_dev *agdev = func_to_agdev(fn);
> -
> -       if (intf == agdev->ac_intf)
> -               return agdev->ac_alt;
> -       else if (intf == agdev->as_out_intf)
> -               return agdev->as_out_alt;
> -       else if (intf == agdev->as_in_intf)
> -               return agdev->as_in_alt;
> +       struct f_uac2 *uac2 = func_to_uac2(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
> +
> +       if (intf == uac2->ac_intf)
> +               return uac2->ac_alt;
> +       else if (intf == uac2->as_out_intf)
> +               return uac2->as_out_alt;
> +       else if (intf == uac2->as_in_intf)
> +               return uac2->as_in_alt;
>         else
>                 dev_err(&agdev->gadget->dev,
>                         "%s:%d Invalid Interface %d!\n",
> @@ -1216,21 +671,19 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  static void
>  afunc_disable(struct usb_function *fn)
>  {
> -       struct audio_dev *agdev = func_to_agdev(fn);
> -       struct snd_uac2_chip *uac2 = &agdev->uac2;
> -
> -       free_ep(&uac2->p_prm, agdev->in_ep);
> -       agdev->as_in_alt = 0;
> +       struct f_uac2 *uac2 = func_to_uac2(fn);
>
> -       free_ep(&uac2->c_prm, agdev->out_ep);
> -       agdev->as_out_alt = 0;
> +       uac2->as_in_alt = 0;
> +       uac2->as_out_alt = 0;
> +       u_audio_stop_capture(&uac2->g_audio);
> +       u_audio_stop_playback(&uac2->g_audio);
>  }
>
>  static int
>  in_rq_cur(struct usb_function *fn, const struct usb_ctrlrequest *cr)
>  {
>         struct usb_request *req = fn->config->cdev->req;
> -       struct audio_dev *agdev = func_to_agdev(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
>         struct f_uac2_opts *opts;
>         u16 w_length = le16_to_cpu(cr->wLength);
>         u16 w_index = le16_to_cpu(cr->wIndex);
> @@ -1240,7 +693,7 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>         int value = -EOPNOTSUPP;
>         int p_srate, c_srate;
>
> -       opts = agdev_to_uac2_opts(agdev);
> +       opts = g_audio_to_uac2_opts(agdev);
>         p_srate = opts->p_srate;
>         c_srate = opts->c_srate;
>
> @@ -1271,7 +724,7 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  in_rq_range(struct usb_function *fn, const struct usb_ctrlrequest *cr)
>  {
>         struct usb_request *req = fn->config->cdev->req;
> -       struct audio_dev *agdev = func_to_agdev(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
>         struct f_uac2_opts *opts;
>         u16 w_length = le16_to_cpu(cr->wLength);
>         u16 w_index = le16_to_cpu(cr->wIndex);
> @@ -1282,7 +735,7 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>         int value = -EOPNOTSUPP;
>         int p_srate, c_srate;
>
> -       opts = agdev_to_uac2_opts(agdev);
> +       opts = g_audio_to_uac2_opts(agdev);
>         p_srate = opts->p_srate;
>         c_srate = opts->c_srate;
>
> @@ -1336,11 +789,12 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  static int
>  setup_rq_inf(struct usb_function *fn, const struct usb_ctrlrequest *cr)
>  {
> -       struct audio_dev *agdev = func_to_agdev(fn);
> +       struct f_uac2 *uac2 = func_to_uac2(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
>         u16 w_index = le16_to_cpu(cr->wIndex);
>         u8 intf = w_index & 0xff;
>
> -       if (intf != agdev->ac_intf) {
> +       if (intf != uac2->ac_intf) {
>                 dev_err(&agdev->gadget->dev,
>                         "%s:%d Error!\n", __func__, __LINE__);
>                 return -EOPNOTSUPP;
> @@ -1358,7 +812,7 @@ static void set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts,
>  afunc_setup(struct usb_function *fn, const struct usb_ctrlrequest *cr)
>  {
>         struct usb_composite_dev *cdev = fn->config->cdev;
> -       struct audio_dev *agdev = func_to_agdev(fn);
> +       struct g_audio *agdev = func_to_g_audio(fn);
>         struct usb_request *req = cdev->req;
>         u16 w_length = le16_to_cpu(cr->wLength);
>         int value = -EOPNOTSUPP;
> @@ -1504,10 +958,10 @@ static struct usb_function_instance *afunc_alloc_inst(void)
>
>  static void afunc_free(struct usb_function *f)
>  {
> -       struct audio_dev *agdev;
> +       struct g_audio *agdev;
>         struct f_uac2_opts *opts;
>
> -       agdev = func_to_agdev(f);
> +       agdev = func_to_g_audio(f);
>         opts = container_of(f->fi, struct f_uac2_opts, func_inst);
>         kfree(agdev);
>         mutex_lock(&opts->lock);
> @@ -1517,17 +971,9 @@ static void afunc_free(struct usb_function *f)
>
>  static void afunc_unbind(struct usb_configuration *c, struct usb_function *f)
>  {
> -       struct audio_dev *agdev = func_to_agdev(f);
> -       struct uac2_rtd_params *prm;
> -
> -       snd_uac2_remove(agdev);
> -
> -       prm = &agdev->uac2.p_prm;
> -       kfree(prm->rbuf);
> +       struct g_audio *agdev = func_to_g_audio(f);
>
> -       prm = &agdev->uac2.c_prm;
> -       kfree(prm->rbuf);
> -       kfree(prm->ureq);
> +       g_audio_cleanup(agdev);
>         usb_free_all_descriptors(f);
>
>         agdev->gadget = NULL;
> @@ -1535,11 +981,11 @@ static void afunc_unbind(struct usb_configuration *c, struct usb_function *f)
>
>  static struct usb_function *afunc_alloc(struct usb_function_instance *fi)
>  {
> -       struct audio_dev *agdev;
> +       struct f_uac2   *uac2;
>         struct f_uac2_opts *opts;
>
> -       agdev = kzalloc(sizeof(*agdev), GFP_KERNEL);
> -       if (agdev == NULL)
> +       uac2 = kzalloc(sizeof(*uac2), GFP_KERNEL);
> +       if (uac2 == NULL)
>                 return ERR_PTR(-ENOMEM);
>
>         opts = container_of(fi, struct f_uac2_opts, func_inst);
> @@ -1547,19 +993,20 @@ static struct usb_function *afunc_alloc(struct usb_function_instance *fi)
>         ++opts->refcnt;
>         mutex_unlock(&opts->lock);
>
> -       agdev->func.name = "uac2_func";
> -       agdev->func.bind = afunc_bind;
> -       agdev->func.unbind = afunc_unbind;
> -       agdev->func.set_alt = afunc_set_alt;
> -       agdev->func.get_alt = afunc_get_alt;
> -       agdev->func.disable = afunc_disable;
> -       agdev->func.setup = afunc_setup;
> -       agdev->func.free_func = afunc_free;
> +       uac2->g_audio.func.name = "uac2_func";
> +       uac2->g_audio.func.bind = afunc_bind;
> +       uac2->g_audio.func.unbind = afunc_unbind;
> +       uac2->g_audio.func.set_alt = afunc_set_alt;
> +       uac2->g_audio.func.get_alt = afunc_get_alt;
> +       uac2->g_audio.func.disable = afunc_disable;
> +       uac2->g_audio.func.setup = afunc_setup;
> +       uac2->g_audio.func.free_func = afunc_free;
>
> -       return &agdev->func;
> +       return &uac2->g_audio.func;
>  }
>
>  DECLARE_USB_FUNCTION_INIT(uac2, afunc_alloc_inst, afunc_alloc);
>  MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Yadwinder Singh");
>  MODULE_AUTHOR("Jaswinder Singh");
> +MODULE_AUTHOR("Ruslan Bilovol");
>
drivers/usb/gadget/function/f_uac2.c  | 721 ++++------------------------------

Basically you move out ALSA sound card implementation and  %s/agdev/uac2/
I am not sure churn warrants a MODULE_AUTHOR. People have made far
more important contribution to the UAC2,


> diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
> new file mode 100644
> index 0000000..8ee65b8
> --- /dev/null
> +++ b/drivers/usb/gadget/function/u_audio.c
> @@ -0,0 +1,661 @@
> +/*
> + * u_audio.c -- interface to USB gadget "ALSA sound card" utilities
> + *
> + * Copyright (C) 2016
> + * Author: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx>
> + *
> + * Based on f_uac2.c which is:
> + *    Copyright (C) 2011
> + *    Yadwinder Singh (yadi.brar01@xxxxxxxxx)
> + *    Jaswinder Singh (jaswinder.singh@xxxxxxxxxx)
> + *
Again this is not "based on", rather where you paste the code you cut
from f_uac2.c
Of course you also pad it with minor changes to make it useful to your
uac1 code. I am not happy with losing copyright on the sound card
implementation for the UAC drivers.

> + * 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");
> diff --git a/drivers/usb/gadget/function/u_audio.h b/drivers/usb/gadget/function/u_audio.h
> new file mode 100644
> index 0000000..07e1378
> --- /dev/null
> +++ b/drivers/usb/gadget/function/u_audio.h
> @@ -0,0 +1,95 @@
> +/*
> + * u_audio.h -- interface to USB gadget "ALSA sound card" utilities
> + *
> + * Copyright (C) 2016
> + * Author: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx>
> + *
> + * 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.
> + *
> + */
> +
> +#ifndef __U_AUDIO_H
> +#define __U_AUDIO_H
> +
> +#include <linux/usb/composite.h>
> +
> +struct uac_params {
> +       /* playback */
> +       int p_chmask;   /* channel mask */
> +       int p_srate;    /* rate in Hz */
> +       int p_ssize;    /* sample size */
> +
> +       /* capture */
> +       int c_chmask;   /* channel mask */
> +       int c_srate;    /* rate in Hz */
> +       int c_ssize;    /* sample size */
> +
> +       int req_number; /* number of preallocated requests */
> +};
> +
> +struct g_audio {
> +       struct usb_function func;
> +       struct usb_gadget *gadget;
> +
> +       struct usb_ep *in_ep;
> +       struct usb_ep *out_ep;
> +
> +       /* Max packet size for all in_ep possible speeds */
> +       unsigned int in_ep_maxpsize;
> +       /* Max packet size for all out_ep possible speeds */
> +       unsigned int out_ep_maxpsize;
> +
> +       /* The ALSA Sound Card it represents on the USB-Client side */
> +       struct snd_uac_chip *uac;
> +
> +       struct uac_params params;
> +};
> +
> +static inline struct g_audio *func_to_g_audio(struct usb_function *f)
> +{
> +       return container_of(f, struct g_audio, func);
> +}
> +
> +static inline uint num_channels(uint chanmask)
> +{
> +       uint num = 0;
> +
> +       while (chanmask) {
> +               num += (chanmask & 1);
> +               chanmask >>= 1;
> +       }
> +
> +       return num;
> +}
> +
> +/*
> + * g_audio_setup - initialize one virtual ALSA sound card
> + * @g_audio: struct with filled params, in_ep_maxpsize, out_ep_maxpsize
> + * @pcm_name: the id string for a PCM instance of this sound card
> + * @card_name: name of this soundcard
> + *
> + * This sets up the single virtual ALSA sound card that may be exported by a
> + * gadget driver using this framework.
> + *
> + * Context: may sleep
> + *
> + * Returns zero on success, or a negative error on failure.
> + */
> +int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
> +                                       const char *card_name);
> +void g_audio_cleanup(struct g_audio *g_audio);
> +
> +int u_audio_start_capture(struct g_audio *g_audio);
> +void u_audio_stop_capture(struct g_audio *g_audio);
> +int u_audio_start_playback(struct g_audio *g_audio);
> +void u_audio_stop_playback(struct g_audio *g_audio);
> +
> +#endif /* __U_AUDIO_H */
> diff --git a/drivers/usb/gadget/legacy/Kconfig b/drivers/usb/gadget/legacy/Kconfig
> index 0b36878..5344064 100644
> --- a/drivers/usb/gadget/legacy/Kconfig
> +++ b/drivers/usb/gadget/legacy/Kconfig
> @@ -56,6 +56,7 @@ config USB_AUDIO
>         select SND_PCM
>         select USB_F_UAC1 if GADGET_UAC1
>         select USB_F_UAC2 if !GADGET_UAC1
> +       select USB_U_AUDIO if USB_F_UAC2
>         help
>           This Gadget Audio driver is compatible with USB Audio Class
>           specification 2.0. It implements 1 AudioControl interface,
> --
> 1.9.1
>
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