text: /*
   * f_audio.c -- USB Audio class function driver
    *
   * Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
   * Copyright (C) 2008 Analog Devices, Inc
   *
   * Enter bugs at http://blackfin.uclinux.org/
   *
   * Licensed under the GPL-2 or later.
   */
  
  #include <linux/slab.h>
  #include <linux/kernel.h>
  #include <linux/device.h>
  #include <asm/atomic.h>
  
  #include "u_audio.h"
  
  #define OUT_EP_MAX_PACKET_SIZE	200
  static int req_buf_size = OUT_EP_MAX_PACKET_SIZE;
  module_param(req_buf_size, int, S_IRUGO);
  MODULE_PARM_DESC(req_buf_size, "ISO OUT endpoint request buffer size");
  
  static int req_count = 256;
  module_param(req_count, int, S_IRUGO);
  MODULE_PARM_DESC(req_count, "ISO OUT endpoint request count");
  
  static int audio_buf_size = 48000;
  module_param(audio_buf_size, int, S_IRUGO);
  MODULE_PARM_DESC(audio_buf_size, "Audio buffer size");
  
  static int generic_set_cmd(struct usb_audio_control *con, u8 cmd, int value);
  static int generic_get_cmd(struct usb_audio_control *con, u8 cmd);
  
  /*
   * DESCRIPTORS ... most are static, but strings and full
   * configuration descriptors are built on demand.
   */
  
  /*
   * We have two interfaces- AudioControl and AudioStreaming
   * TODO: only supcard playback currently
   */
  #define F_AUDIO_AC_INTERFACE	0
  #define F_AUDIO_AS_INTERFACE	1
  #define F_AUDIO_NUM_INTERFACES	2
  
  /* B.3.1  Standard AC Interface Descriptor */
  static struct usb_interface_descriptor ac_interface_desc __initdata = {
  	.bLength =		USB_DT_INTERFACE_SIZE,
  	.bDescriptorType =	USB_DT_INTERFACE,
  	.bNumEndpoints =	0,
  	.bInterfaceClass =	USB_CLASS_AUDIO,
  	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOCONTROL,
  };
  
  DECLARE_UAC_AC_HEADER_DESCRIPTOR(2);
  
  #define UAC_DT_AC_HEADER_LENGTH	UAC_DT_AC_HEADER_SIZE(F_AUDIO_NUM_INTERFACES)
  /* 1 input terminal, 1 output terminal and 1 feature unit */
  #define UAC_DT_TOTAL_LENGTH (UAC_DT_AC_HEADER_LENGTH + UAC_DT_INPUT_TERMINAL_SIZE \
  	+ UAC_DT_OUTPUT_TERMINAL_SIZE + UAC_DT_FEATURE_UNIT_SIZE(0))
  /* B.3.2  Class-Specific AC Interface Descriptor */
  static struct uac1_ac_header_descriptor_2 ac_header_desc = {
  	.bLength =		UAC_DT_AC_HEADER_LENGTH,
  	.bDescriptorType =	USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype =	UAC_HEADER,
  	.bcdADC =		__constant_cpu_to_le16(0x0100),
  	.wTotalLength =		__constant_cpu_to_le16(UAC_DT_TOTAL_LENGTH),
  	.bInCollection =	F_AUDIO_NUM_INTERFACES,
  	.baInterfaceNr = {
  		[0] =		F_AUDIO_AC_INTERFACE,
  		[1] =		F_AUDIO_AS_INTERFACE,
  	}
  };
  
  #define INPUT_TERMINAL_ID	1
  static struct uac_input_terminal_descriptor input_terminal_desc = {
  	.bLength =		UAC_DT_INPUT_TERMINAL_SIZE,
  	.bDescriptorType =	USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype =	UAC_INPUT_TERMINAL,
  	.bTerminalID =		INPUT_TERMINAL_ID,
  	.wTerminalType =	UAC_TERMINAL_STREAMING,
  	.bAssocTerminal =	0,
  	.wChannelConfig =	0x3,
  };
  
  DECLARE_UAC_FEATURE_UNIT_DESCRIPTOR(0);
  
  #define FEATURE_UNIT_ID		2
  static struct uac_feature_unit_descriptor_0 feature_unit_desc = {
  	.bLength		= UAC_DT_FEATURE_UNIT_SIZE(0),
  	.bDescriptorType	= USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype	= UAC_FEATURE_UNIT,
  	.bUnitID		= FEATURE_UNIT_ID,
  	.bSourceID		= INPUT_TERMINAL_ID,
  	.bControlSize		= 2,
  	.bmaControls[0]		= (UAC_FU_MUTE | UAC_FU_VOLUME),
  };
  
  static struct usb_audio_control mute_control = {
  	.list = LIST_HEAD_INIT(mute_control.list),
  	.name = "Mute Control",
  	.type = UAC_FU_MUTE,
  	/* Todo: add real Mute control code */
  	.set = generic_set_cmd,
  	.get = generic_get_cmd,
  };
  
  static struct usb_audio_control volume_control = {
  	.list = LIST_HEAD_INIT(volume_control.list),
  	.name = "Volume Control",
  	.type = UAC_FU_VOLUME,
  	/* Todo: add real Volume control code */
  	.set = generic_set_cmd,
  	.get = generic_get_cmd,
  };
  
  static struct usb_audio_control_selector feature_unit = {
  	.list = LIST_HEAD_INIT(feature_unit.list),
  	.id = FEATURE_UNIT_ID,
  	.name = "Mute & Volume Control",
  	.type = UAC_FEATURE_UNIT,
  	.desc = (struct usb_descriptor_header *)&feature_unit_desc,
  };
  
  #define OUTPUT_TERMINAL_ID	3
  static struct uac1_output_terminal_descriptor output_terminal_desc = {
  	.bLength		= UAC_DT_OUTPUT_TERMINAL_SIZE,
  	.bDescriptorType	= USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype	= UAC_OUTPUT_TERMINAL,
  	.bTerminalID		= OUTPUT_TERMINAL_ID,
  	.wTerminalType		= UAC_OUTPUT_TERMINAL_SPEAKER,
  	.bAssocTerminal		= FEATURE_UNIT_ID,
  	.bSourceID		= FEATURE_UNIT_ID,
  };
  
  /* B.4.1  Standard AS Interface Descriptor */
  static struct usb_interface_descriptor as_interface_alt_0_desc = {
  	.bLength =		USB_DT_INTERFACE_SIZE,
  	.bDescriptorType =	USB_DT_INTERFACE,
  	.bAlternateSetting =	0,
  	.bNumEndpoints =	0,
  	.bInterfaceClass =	USB_CLASS_AUDIO,
  	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
  };
  
  static struct usb_interface_descriptor as_interface_alt_1_desc = {
  	.bLength =		USB_DT_INTERFACE_SIZE,
  	.bDescriptorType =	USB_DT_INTERFACE,
  	.bAlternateSetting =	1,
  	.bNumEndpoints =	1,
  	.bInterfaceClass =	USB_CLASS_AUDIO,
  	.bInterfaceSubClass =	USB_SUBCLASS_AUDIOSTREAMING,
  };
  
  /* B.4.2  Class-Specific AS Interface Descriptor */
  static struct uac1_as_header_descriptor as_header_desc = {
  	.bLength =		UAC_DT_AS_HEADER_SIZE,
  	.bDescriptorType =	USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype =	UAC_AS_GENERAL,
  	.bTerminalLink =	INPUT_TERMINAL_ID,
  	.bDelay =		1,
  	.wFormatTag =		UAC_FORMAT_TYPE_I_PCM,
  };
  
  DECLARE_UAC_FORMAT_TYPE_I_DISCRETE_DESC(1);
  
  static struct uac_format_type_i_discrete_descriptor_1 as_type_i_desc = {
  	.bLength =		UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(1),
  	.bDescriptorType =	USB_DT_CS_INTERFACE,
  	.bDescriptorSubtype =	UAC_FORMAT_TYPE,
  	.bFormatType =		UAC_FORMAT_TYPE_I,
  	.bSubframeSize =	2,
  	.bBitResolution =	16,
  	.bSamFreqType =		1,
  };
  
  /* Standard ISO OUT Endpoint Descriptor */
  static struct usb_endpoint_descriptor as_out_ep_desc  = {
  	.bLength =		USB_DT_ENDPOINT_AUDIO_SIZE,
  	.bDescriptorType =	USB_DT_ENDPOINT,
  	.bEndpointAddress =	USB_DIR_OUT,
  	.bmAttributes =		USB_ENDPOINT_SYNC_ADAPTIVE
  				| USB_ENDPOINT_XFER_ISOC,
  	.wMaxPacketSize =	__constant_cpu_to_le16(OUT_EP_MAX_PACKET_SIZE),
  	.bInterval =		4,
  };
  
  /* Class-specific AS ISO OUT Endpoint Descriptor */
  static struct uac_iso_endpoint_descriptor as_iso_out_desc __initdata = {
  	.bLength =		UAC_ISO_ENDPOINT_DESC_SIZE,
  	.bDescriptorType =	USB_DT_CS_ENDPOINT,
  	.bDescriptorSubtype =	UAC_EP_GENERAL,
  	.bmAttributes = 	1,
  	.bLockDelayUnits =	1,
  	.wLockDelay =		__constant_cpu_to_le16(1),
  };
  
  static struct usb_descriptor_header *f_audio_desc[] __initdata = {
  	(struct usb_descriptor_header *)&ac_interface_desc,
  	(struct usb_descriptor_header *)&ac_header_desc,
  
  	(struct usb_descriptor_header *)&input_terminal_desc,
  	(struct usb_descriptor_header *)&output_terminal_desc,
  	(struct usb_descriptor_header *)&feature_unit_desc,
  
  	(struct usb_descriptor_header *)&as_interface_alt_0_desc,
  	(struct usb_descriptor_header *)&as_interface_alt_1_desc,
  	(struct usb_descriptor_header *)&as_header_desc,
  
  	(struct usb_descriptor_header *)&as_type_i_desc,
  
  	(struct usb_descriptor_header *)&as_out_ep_desc,
  	(struct usb_descriptor_header *)&as_iso_out_desc,
  	NULL,
  };
  
  /* string IDs are assigned dynamically */
  
  #define STRING_MANUFACTURER_IDX		0
  #define STRING_PRODUCT_IDX		1
  
  static char manufacturer[50];
  
  static struct usb_string strings_dev[] = {
  	[STRING_MANUFACTURER_IDX].s = manufacturer,
  	[STRING_PRODUCT_IDX].s = DRIVER_DESC,
  	{  } /* end of list */
  };
  
  static struct usb_gadget_strings stringtab_dev = {
  	.language	= 0x0409,	/* en-us */
  	.strings	= strings_dev,
  };
  
  static struct usb_gadget_strings *audio_strings[] = {
  	&stringtab_dev,
  	NULL,
  };
  
  /*
   * This function is an ALSA sound card following USB Audio Class Spec 1.0.
   */
  
  /*-------------------------------------------------------------------------*/
  struct f_audio_buf {
  	u8 *buf;
  	int actual;
  	struct list_head list;
  };
  
  static struct f_audio_buf *f_audio_buffer_alloc(int buf_size)
  {
  	struct f_audio_buf *copy_buf;
  
  	copy_buf = kzalloc(sizeof *copy_buf, GFP_ATOMIC);
  	if (!copy_buf)
  		return ERR_PTR(-ENOMEM);
  
  	copy_buf->buf = kzalloc(buf_size, GFP_ATOMIC);
  	if (!copy_buf->buf) {
  		kfree(copy_buf);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	return copy_buf;
  }
  
  static void f_audio_buffer_free(struct f_audio_buf *audio_buf)
  {
  	kfree(audio_buf->buf);
  	kfree(audio_buf);
  }
  /*-------------------------------------------------------------------------*/
  
  struct f_audio {
  	struct gaudio			card;
  
  	/* endpoints handle full and/or high speeds */
  	struct usb_ep			*out_ep;
  	struct usb_endpoint_descriptor	*out_desc;
  
  	spinlock_t			lock;
  	struct f_audio_buf *copy_buf;
  	struct work_struct playback_work;
  	struct list_head play_queue;
  
  	/* Control Set command */
  	struct list_head cs;
  	u8 set_cmd;
  	struct usb_audio_control *set_con;
  };
  
  static inline struct f_audio *func_to_audio(struct usb_function *f)
  {
  	return container_of(f, struct f_audio, card.func);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void f_audio_playback_work(struct work_struct *data)
  {
  	struct f_audio *audio = container_of(data, struct f_audio,
  					playback_work);
  	struct f_audio_buf *play_buf;
  
  	spin_lock_irq(&audio->lock);
  	if (list_empty(&audio->play_queue)) {
  		spin_unlock_irq(&audio->lock);
  		return;
  	}
  	play_buf = list_first_entry(&audio->play_queue,
  			struct f_audio_buf, list);
  	list_del(&play_buf->list);
  	spin_unlock_irq(&audio->lock);
  
  	u_audio_playback(&audio->card, play_buf->buf, play_buf->actual);
  	f_audio_buffer_free(play_buf);
  }
  
  static int f_audio_out_ep_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct f_audio *audio = req->context;
  	struct usb_composite_dev *cdev = audio->card.func.config->cdev;
  	struct f_audio_buf *copy_buf = audio->copy_buf;
  	int err;
  
  	if (!copy_buf)
  		return -EINVAL;
  
  	/* Copy buffer is full, add it to the play_queue */
  	if (audio_buf_size - copy_buf->actual < req->actual) {
  		list_add_tail(&copy_buf->list, &audio->play_queue);
  		schedule_work(&audio->playback_work);
  		copy_buf = f_audio_buffer_alloc(audio_buf_size);
  		if (IS_ERR(copy_buf))
  			return -ENOMEM;
  	}
  
  	memcpy(copy_buf->buf + copy_buf->actual, req->buf, req->actual);
  	copy_buf->actual += req->actual;
  	audio->copy_buf = copy_buf;
  
  	err = usb_ep_queue(ep, req, GFP_ATOMIC);
  	if (err)
  		ERROR(cdev, "%s queue req: %d\n", ep->name, err);
  
  	return 0;
  
  }
  
  static void f_audio_complete(struct usb_ep *ep, struct usb_request *req)
  {
  	struct f_audio *audio = req->context;
  	int status = req->status;
  	u32 data = 0;
  	struct usb_ep *out_ep = audio->out_ep;
  
  	switch (status) {
  
  	case 0:				/* normal completion? */
  		if (ep == out_ep)
  			f_audio_out_ep_complete(ep, req);
  		else if (audio->set_con) {
  			memcpy(&data, req->buf, req->length);
  			audio->set_con->set(audio->set_con, audio->set_cmd,
  					le16_to_cpu(data));
  			audio->set_con = NULL;
  		}
  		break;
  	default:
  		break;
  	}
  }
  
  static int audio_set_intf_req(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct f_audio		*audio = func_to_audio(f);
  	struct usb_composite_dev *cdev = f->config->cdev;
  	struct usb_request	*req = cdev->req;
  	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
  	u16			len = le16_to_cpu(ctrl->wLength);
  	u16			w_value = le16_to_cpu(ctrl->wValue);
  	u8			con_sel = (w_value >> 8) & 0xFF;
  	u8			cmd = (ctrl->bRequest & 0x0F);
  	struct usb_audio_control_selector *cs;
  	struct usb_audio_control *con;
  
  	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
  			ctrl->bRequest, w_value, len, id);
  
  	list_for_each_entry(cs, &audio->cs, list) {
  		if (cs->id == id) {
  			list_for_each_entry(con, &cs->control, list) {
  				if (con->type == con_sel) {
  					audio->set_con = con;
  					break;
  				}
  			}
  			break;
  		}
  	}
  
  	audio->set_cmd = cmd;
  	req->context = audio;
  	req->complete = f_audio_complete;
  
  	return len;
  }
  
  static int audio_get_intf_req(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct f_audio		*audio = func_to_audio(f);
  	struct usb_composite_dev *cdev = f->config->cdev;
  	struct usb_request	*req = cdev->req;
  	int			value = -EOPNOTSUPP;
  	u8			id = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
  	u16			len = le16_to_cpu(ctrl->wLength);
  	u16			w_value = le16_to_cpu(ctrl->wValue);
  	u8			con_sel = (w_value >> 8) & 0xFF;
  	u8			cmd = (ctrl->bRequest & 0x0F);
  	struct usb_audio_control_selector *cs;
  	struct usb_audio_control *con;
  
  	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, entity %d\n",
  			ctrl->bRequest, w_value, len, id);
  
  	list_for_each_entry(cs, &audio->cs, list) {
  		if (cs->id == id) {
  			list_for_each_entry(con, &cs->control, list) {
  				if (con->type == con_sel && con->get) {
  					value = con->get(con, cmd);
  					break;
  				}
  			}
  			break;
  		}
  	}
  
  	req->context = audio;
  	req->complete = f_audio_complete;
  	memcpy(req->buf, &value, len);
  
  	return len;
  }
  
  static int audio_set_endpoint_req(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct usb_composite_dev *cdev = f->config->cdev;
  	int			value = -EOPNOTSUPP;
  	u16			ep = le16_to_cpu(ctrl->wIndex);
  	u16			len = le16_to_cpu(ctrl->wLength);
  	u16			w_value = le16_to_cpu(ctrl->wValue);
  
  	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
  			ctrl->bRequest, w_value, len, ep);
  
  	switch (ctrl->bRequest) {
  	case UAC_SET_CUR:
  		value = 0;
  		break;
  
  	case UAC_SET_MIN:
  		break;
  
  	case UAC_SET_MAX:
  		break;
  
  	case UAC_SET_RES:
  		break;
  
  	case UAC_SET_MEM:
  		break;
  
  	default:
  		break;
  	}
  
  	return value;
  }
  
  static int audio_get_endpoint_req(struct usb_function *f,
  		const struct usb_ctrlrequest *ctrl)
  {
  	struct usb_composite_dev *cdev = f->config->cdev;
  	int value = -EOPNOTSUPP;
  	u8 ep = ((le16_to_cpu(ctrl->wIndex) >> 8) & 0xFF);
  	u16 len = le16_to_cpu(ctrl->wLength);
  	u16 w_value = le16_to_cpu(ctrl->wValue);
  
  	DBG(cdev, "bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
  			ctrl->bRequest, w_value, len, ep);
  
  	switch (ctrl->bRequest) {
  	case UAC_GET_CUR:
  	case UAC_GET_MIN:
  	case UAC_GET_MAX:
  	case UAC_GET_RES:
  		value = 3;
  		break;
  	case UAC_GET_MEM:
  		break;
  	default:
  		break;
  	}
  
  	return value;
  }
  
  static int
  f_audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
  {
  	struct usb_composite_dev *cdev = f->config->cdev;
  	struct usb_request	*req = cdev->req;
  	int			value = -EOPNOTSUPP;
  	u16			w_index = le16_to_cpu(ctrl->wIndex);
  	u16			w_value = le16_to_cpu(ctrl->wValue);
  	u16			w_length = le16_to_cpu(ctrl->wLength);
  
  	/* composite driver infrastructure handles everything; interface
  	 * activation uses set_alt().
  	 */
  	switch (ctrl->bRequestType) {
  	case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
  		value = audio_set_intf_req(f, ctrl);
  		break;
  
  	case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
  		value = audio_get_intf_req(f, ctrl);
  		break;
  
  	case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
  		value = audio_set_endpoint_req(f, ctrl);
  		break;
  
  	case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
  		value = audio_get_endpoint_req(f, ctrl);
  		break;
  
  	default:
  		ERROR(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
  			ctrl->bRequestType, ctrl->bRequest,
  			w_value, w_index, w_length);
  	}
  
  	/* respond with data transfer or status phase? */
  	if (value >= 0) {
  		DBG(cdev, "audio req%02x.%02x v%04x i%04x l%d\n",
  			ctrl->bRequestType, ctrl->bRequest,
  			w_value, w_index, w_length);
  		req->zero = 0;
  		req->length = value;
  		value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
  		if (value < 0)
  			ERROR(cdev, "audio response on err %d\n", value);
  	}
  
  	/* device either stalls (value < 0) or reports success */
  	return value;
  }
  
  static int f_audio_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
  {
  	struct f_audio		*audio = func_to_audio(f);
  	struct usb_composite_dev *cdev = f->config->cdev;
  	struct usb_ep *out_ep = audio->out_ep;
  	struct usb_request *req;
  	int i = 0, err = 0;
  
  	DBG(cdev, "intf %d, alt %d\n", intf, alt);
  
  	if (intf == 1) {
  		if (alt == 1) {
  			usb_ep_enable(out_ep, audio->out_desc);
  			out_ep->driver_data = audio;
  			audio->copy_buf = f_audio_buffer_alloc(audio_buf_size);
  			if (IS_ERR(audio->copy_buf))
  				return -ENOMEM;
  
  			/*
  			 * allocate a bunch of read buffers
  			 * and queue them all at once.
  			 */
  			for (i = 0; i < req_count && err == 0; i++) {
  				req = usb_ep_alloc_request(out_ep, GFP_ATOMIC);
  				if (req) {
  					req->buf = kzalloc(req_buf_size,
  							GFP_ATOMIC);
  					if (req->buf) {
  						req->length = req_buf_size;
  						req->context = audio;
  						req->complete =
  							f_audio_complete;
  						err = usb_ep_queue(out_ep,
  							req, GFP_ATOMIC);
  						if (err)
  							ERROR(cdev,
  							"%s queue req: %d\n",
  							out_ep->name, err);
  					} else
  						err = -ENOMEM;
  				} else
  					err = -ENOMEM;
  			}
  
  		} else {
  			struct f_audio_buf *copy_buf = audio->copy_buf;
  			if (copy_buf) {
  				list_add_tail(&copy_buf->list,
  						&audio->play_queue);
  				schedule_work(&audio->playback_work);
  			}
  		}
  	}
  
  	return err;
  }
  
  static void f_audio_disable(struct usb_function *f)
  {
  	return;
  }
  
  /*-------------------------------------------------------------------------*/
  
  static void f_audio_build_desc(struct f_audio *audio)
  {
  	struct gaudio *card = &audio->card;
  	u8 *sam_freq;
  	int rate;
  
  	/* Set channel numbers */
  	input_terminal_desc.bNrChannels = u_audio_get_playback_channels(card);
  	as_type_i_desc.bNrChannels = u_audio_get_playback_channels(card);
  
  	/* Set sample rates */
  	rate = u_audio_get_playback_rate(card);
  	sam_freq = as_type_i_desc.tSamFreq[0];
  	memcpy(sam_freq, &rate, 3);
  
  	/* Todo: Set Sample bits and other parameters */
  
  	return;
  }
  
  /* audio function driver setup/binding */
  static int __init
  f_audio_bind(struct usb_configuration *c, struct usb_function *f)
  {
  	struct usb_composite_dev *cdev = c->cdev;
  	struct f_audio		*audio = func_to_audio(f);
  	int			status;
  	struct usb_ep		*ep;
  
  	f_audio_build_desc(audio);
  
  	/* allocate instance-specific interface IDs, and patch descriptors */
  	status = usb_interface_id(c, f);
  	if (status < 0)
  		goto fail;
  	ac_interface_desc.bInterfaceNumber = status;
  
  	status = usb_interface_id(c, f);
  	if (status < 0)
  		goto fail;
  	as_interface_alt_0_desc.bInterfaceNumber = status;
  	as_interface_alt_1_desc.bInterfaceNumber = status;
  
  	status = -ENODEV;
  
  	/* allocate instance-specific endpoints */
  	ep = usb_ep_autoconfig(cdev->gadget, &as_out_ep_desc);
  	if (!ep)
  		goto fail;
  	audio->out_ep = ep;
  	ep->driver_data = cdev;	/* claim */
  
  	status = -ENOMEM;
  
  	/* supcard all relevant hardware speeds... we expect that when
  	 * hardware is dual speed, all bulk-capable endpoints work at
  	 * both speeds
  	 */
  
  	/* copy descriptors, and track endpoint copies */
  	if (gadget_is_dualspeed(c->cdev->gadget)) {
  		c->highspeed = true;
  		f->hs_descriptors = usb_copy_descriptors(f_audio_desc);
  	} else
  		f->descriptors = usb_copy_descriptors(f_audio_desc);
  
  	return 0;
  
  fail:
  
  	return status;
  }
  
  static void
  f_audio_unbind(struct usb_configuration *c, struct usb_function *f)
  {
  	struct f_audio		*audio = func_to_audio(f);
  
  	usb_free_descriptors(f->descriptors);
  	usb_free_descriptors(f->hs_descriptors);
  	kfree(audio);
  }
  
  /*-------------------------------------------------------------------------*/
  
  static int generic_set_cmd(struct usb_audio_control *con, u8 cmd, int value)
  {
  	con->data[cmd] = value;
  
  	return 0;
  }
  
  static int generic_get_cmd(struct usb_audio_control *con, u8 cmd)
  {
  	return con->data[cmd];
  }
  
  /* Todo: add more control selecotor dynamically */
  int __init control_selector_init(struct f_audio *audio)
  {
  	INIT_LIST_HEAD(&audio->cs);
  	list_add(&feature_unit.list, &audio->cs);
  
  	INIT_LIST_HEAD(&feature_unit.control);
  	list_add(&mute_control.list, &feature_unit.control);
  	list_add(&volume_control.list, &feature_unit.control);
  
  	volume_control.data[UAC__CUR] = 0xffc0;
  	volume_control.data[UAC__MIN] = 0xe3a0;
  	volume_control.data[UAC__MAX] = 0xfff0;
  	volume_control.data[UAC__RES] = 0x0030;
  
  	return 0;
  }
  
  /**
   * audio_bind_config - add USB audio function to a configuration
   * @c: the configuration to supcard the USB audio function
   * Context: single threaded during gadget setup
   *
   * Returns zero on success, else negative errno.
   */
  int __init audio_bind_config(struct usb_configuration *c)
  {
  	struct f_audio *audio;
  	int status;
  
  	/* allocate and initialize one new instance */
  	audio = kzalloc(sizeof *audio, GFP_KERNEL);
  	if (!audio)
  		return -ENOMEM;
  
  	audio->card.func.name = "g_audio";
  	audio->card.gadget = c->cdev->gadget;
  
  	INIT_LIST_HEAD(&audio->play_queue);
  	spin_lock_init(&audio->lock);
  
  	/* set up ASLA audio devices */
  	status = gaudio_setup(&audio->card);
  	if (status < 0)
  		goto setup_fail;
  
  	audio->card.func.strings = audio_strings;
  	audio->card.func.bind = f_audio_bind;
  	audio->card.func.unbind = f_audio_unbind;
  	audio->card.func.set_alt = f_audio_set_alt;
  	audio->card.func.setup = f_audio_setup;
  	audio->card.func.disable = f_audio_disable;
  	audio->out_desc = &as_out_ep_desc;
  
  	control_selector_init(audio);
  
  	INIT_WORK(&audio->playback_work, f_audio_playback_work);
  
  	status = usb_add_function(c, &audio->card.func);
  	if (status)
  		goto add_fail;
  
  	INFO(c->cdev, "audio_buf_size %d, req_buf_size %d, req_count %d\n",
  		audio_buf_size, req_buf_size, req_count);
  
  	return status;
  
  add_fail:
  	gaudio_cleanup();
  setup_fail:
  	kfree(audio);
  	return status;
  }
  