// SPDX-License-Identifier: GPL-2.0+
/*
 * f_uac1.c -- USB Audio Class 1.0 Function (using u_audio API)
 *
 * Copyright (C) 2016 Ruslan Bilovol <ruslan.bilovol@gmail.com>
 * Copyright (C) 2021 Julian Scheel <julian@jusst.de>
 *
 * This driver doesn't expect any real Audio codec to be present
 * on the device - the audio streams are simply sinked to and
 * sourced from a virtual ALSA sound card created.
 *
 * This file is based on f_uac1.c which is
 *   Copyright (C) 2008 Bryan Wu <cooloney@kernel.org>
 *   Copyright (C) 2008 Analog Devices, Inc
 */

#include <linux/usb/audio.h>
#include <linux/module.h>

#include "u_audio.h"
#include "u_uac1.h"

/* UAC1 spec: 3.7.2.3 Audio Channel Cluster Format */
#define UAC1_CHANNEL_MASK 0x0FFF

#define USB_OUT_FU_ID   (out_feature_unit_desc->bUnitID)
#define USB_IN_FU_ID    (in_feature_unit_desc->bUnitID)

#define EPIN_EN(_opts) ((_opts)->p_chmask != 0)
#define EPOUT_EN(_opts) ((_opts)->c_chmask != 0)
#define FUIN_EN(_opts) ((_opts)->p_mute_present \
                        || (_opts)->p_volume_present)
#define FUOUT_EN(_opts) ((_opts)->c_mute_present \
                        || (_opts)->c_volume_present)

struct f_uac1 {
        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() */

        struct usb_ctrlrequest setup_cr;        /* will be used in data stage */

        /* Interrupt IN endpoint of AC interface */
        struct usb_ep   *int_ep;
        atomic_t        int_count;
        int ctl_id;             /* EP id */
        int c_srate;    /* current capture srate */
        int p_srate;    /* current playback prate */
};

static inline struct f_uac1 *func_to_uac1(struct usb_function *f)
{
        return container_of(f, struct f_uac1, g_audio.func);
}

static inline struct f_uac1_opts *g_audio_to_uac1_opts(struct g_audio *audio)
{
        return container_of(audio->func.fi, struct f_uac1_opts, func_inst);
}

/*
 * DESCRIPTORS ... most are static, but strings and full
 * configuration descriptors are built on demand.
 */

/*
 * We have three interfaces - one AudioControl and two AudioStreaming
 *
 * The driver implements a simple UAC_1 topology.
 * USB-OUT -> IT_1 -> OT_2 -> ALSA_Capture
 * ALSA_Playback -> IT_3 -> OT_4 -> USB-IN
 */

/* B.3.1  Standard AC Interface Descriptor */
static struct usb_interface_descriptor ac_interface_desc = {
        .bLength =              USB_DT_INTERFACE_SIZE,
        .bDescriptorType =      USB_DT_INTERFACE,
        /* .bNumEndpoints =     DYNAMIC */
        .bInterfaceClass =      USB_CLASS_AUDIO,
        .bInterfaceSubClass =   USB_SUBCLASS_AUDIOCONTROL,
};

/* B.3.2  Class-Specific AC Interface Descriptor */
static struct uac1_ac_header_descriptor *ac_header_desc;

static struct uac_input_terminal_descriptor usb_out_it_desc = {
        .bLength =              UAC_DT_INPUT_TERMINAL_SIZE,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_INPUT_TERMINAL,
        /* .bTerminalID =       DYNAMIC */
        .wTerminalType =        cpu_to_le16(UAC_TERMINAL_STREAMING),
        .bAssocTerminal =       0,
        .wChannelConfig =       cpu_to_le16(0x3),
};

static struct uac1_output_terminal_descriptor io_out_ot_desc = {
        .bLength                = UAC_DT_OUTPUT_TERMINAL_SIZE,
        .bDescriptorType        = USB_DT_CS_INTERFACE,
        .bDescriptorSubtype     = UAC_OUTPUT_TERMINAL,
        /* .bTerminalID =       DYNAMIC */
        .wTerminalType          = cpu_to_le16(UAC_OUTPUT_TERMINAL_SPEAKER),
        .bAssocTerminal         = 0,
        /* .bSourceID =         DYNAMIC */
};

static struct uac_input_terminal_descriptor io_in_it_desc = {
        .bLength                = UAC_DT_INPUT_TERMINAL_SIZE,
        .bDescriptorType        = USB_DT_CS_INTERFACE,
        .bDescriptorSubtype     = UAC_INPUT_TERMINAL,
        /* .bTerminalID         = DYNAMIC */
        .wTerminalType          = cpu_to_le16(UAC_INPUT_TERMINAL_MICROPHONE),
        .bAssocTerminal         = 0,
        .wChannelConfig         = cpu_to_le16(0x3),
};

static struct uac1_output_terminal_descriptor usb_in_ot_desc = {
        .bLength =              UAC_DT_OUTPUT_TERMINAL_SIZE,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_OUTPUT_TERMINAL,
        /* .bTerminalID =       DYNAMIC */
        .wTerminalType =        cpu_to_le16(UAC_TERMINAL_STREAMING),
        .bAssocTerminal =       0,
        /* .bSourceID =         DYNAMIC */
};

static struct uac_feature_unit_descriptor *in_feature_unit_desc;
static struct uac_feature_unit_descriptor *out_feature_unit_desc;

/* AC IN Interrupt Endpoint */
static struct usb_endpoint_descriptor ac_int_ep_desc = {
        .bLength = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType = USB_DT_ENDPOINT,
        .bEndpointAddress = USB_DIR_IN,
        .bmAttributes = USB_ENDPOINT_XFER_INT,
        .wMaxPacketSize = cpu_to_le16(2),
        .bInterval = 4,
};

/* B.4.1  Standard AS Interface Descriptor */
static struct usb_interface_descriptor as_out_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_out_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,
};

static struct usb_interface_descriptor as_in_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_in_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_out_header_desc = {
        .bLength =              UAC_DT_AS_HEADER_SIZE,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_AS_GENERAL,
        /* .bTerminalLink =     DYNAMIC */
        .bDelay =               1,
        .wFormatTag =           cpu_to_le16(UAC_FORMAT_TYPE_I_PCM),
};

static struct uac1_as_header_descriptor as_in_header_desc = {
        .bLength =              UAC_DT_AS_HEADER_SIZE,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_AS_GENERAL,
        /* .bTerminalLink =     DYNAMIC */
        .bDelay =               1,
        .wFormatTag =           cpu_to_le16(UAC_FORMAT_TYPE_I_PCM),
};

DECLARE_UAC_FORMAT_TYPE_I_DISCRETE_DESC(UAC_MAX_RATES);
#define uac_format_type_i_discrete_descriptor                   \
        uac_format_type_i_discrete_descriptor_##UAC_MAX_RATES

static struct uac_format_type_i_discrete_descriptor as_out_type_i_desc = {
        .bLength =              0, /* filled on rate setup */
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_FORMAT_TYPE,
        .bFormatType =          UAC_FORMAT_TYPE_I,
        .bSubframeSize =        2,
        .bBitResolution =       16,
        .bSamFreqType =         0, /* filled on rate setup */
};

/* 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 =       cpu_to_le16(UAC1_OUT_EP_MAX_PACKET_SIZE),
        .bInterval =            4,
};

/* Class-specific AS ISO OUT Endpoint Descriptor */
static struct uac_iso_endpoint_descriptor as_iso_out_desc = {
        .bLength =              UAC_ISO_ENDPOINT_DESC_SIZE,
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   UAC_EP_GENERAL,
        .bmAttributes =         1,
        .bLockDelayUnits =      1,
        .wLockDelay =           cpu_to_le16(1),
};

static struct uac_format_type_i_discrete_descriptor as_in_type_i_desc = {
        .bLength =              0, /* filled on rate setup */
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubtype =   UAC_FORMAT_TYPE,
        .bFormatType =          UAC_FORMAT_TYPE_I,
        .bSubframeSize =        2,
        .bBitResolution =       16,
        .bSamFreqType =         0, /* filled on rate setup */
};

/* Standard ISO OUT Endpoint Descriptor */
static struct usb_endpoint_descriptor as_in_ep_desc  = {
        .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_SYNC_ASYNC
                                | USB_ENDPOINT_XFER_ISOC,
        .wMaxPacketSize =       cpu_to_le16(UAC1_OUT_EP_MAX_PACKET_SIZE),
        .bInterval =            4,
};

/* Class-specific AS ISO OUT Endpoint Descriptor */
static struct uac_iso_endpoint_descriptor as_iso_in_desc = {
        .bLength =              UAC_ISO_ENDPOINT_DESC_SIZE,
        .bDescriptorType =      USB_DT_CS_ENDPOINT,
        .bDescriptorSubtype =   UAC_EP_GENERAL,
        .bmAttributes =         1,
        .bLockDelayUnits =      0,
        .wLockDelay =           0,
};

static struct usb_descriptor_header *f_audio_desc[] = {
        (struct usb_descriptor_header *)&ac_interface_desc,
        (struct usb_descriptor_header *)&ac_header_desc,

        (struct usb_descriptor_header *)&usb_out_it_desc,
        (struct usb_descriptor_header *)&io_out_ot_desc,
        (struct usb_descriptor_header *)&out_feature_unit_desc,

        (struct usb_descriptor_header *)&io_in_it_desc,
        (struct usb_descriptor_header *)&usb_in_ot_desc,
        (struct usb_descriptor_header *)&in_feature_unit_desc,

        (struct usb_descriptor_header *)&ac_int_ep_desc,

        (struct usb_descriptor_header *)&as_out_interface_alt_0_desc,
        (struct usb_descriptor_header *)&as_out_interface_alt_1_desc,
        (struct usb_descriptor_header *)&as_out_header_desc,

        (struct usb_descriptor_header *)&as_out_type_i_desc,

        (struct usb_descriptor_header *)&as_out_ep_desc,
        (struct usb_descriptor_header *)&as_iso_out_desc,

        (struct usb_descriptor_header *)&as_in_interface_alt_0_desc,
        (struct usb_descriptor_header *)&as_in_interface_alt_1_desc,
        (struct usb_descriptor_header *)&as_in_header_desc,

        (struct usb_descriptor_header *)&as_in_type_i_desc,

        (struct usb_descriptor_header *)&as_in_ep_desc,
        (struct usb_descriptor_header *)&as_iso_in_desc,
        NULL,
};

/* Standard ISO OUT Endpoint Descriptor */
static struct usb_endpoint_descriptor ss_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 =       cpu_to_le16(UAC1_OUT_EP_MAX_PACKET_SIZE),
        .bInterval =            4,
};

static struct usb_ss_ep_comp_descriptor ss_as_out_ep_desc_comp = {
        .bLength                = sizeof(ss_as_out_ep_desc_comp),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
        .bMaxBurst              = 0,
        .bmAttributes           = 0,
        /* wBytesPerInterval = DYNAMIC */
};

/* Standard ISO OUT Endpoint Descriptor */
static struct usb_endpoint_descriptor ss_as_in_ep_desc  = {
        .bLength =              USB_DT_ENDPOINT_AUDIO_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_SYNC_ASYNC
                                | USB_ENDPOINT_XFER_ISOC,
        .wMaxPacketSize =       cpu_to_le16(UAC1_OUT_EP_MAX_PACKET_SIZE),
        .bInterval =            4,
};

static struct usb_ss_ep_comp_descriptor ss_as_in_ep_desc_comp = {
        .bLength                = sizeof(ss_as_in_ep_desc_comp),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,
        .bMaxBurst              = 0,
        .bmAttributes           = 0,
        /* wBytesPerInterval = DYNAMIC */
};

static struct usb_descriptor_header *f_audio_ss_desc[] = {
        (struct usb_descriptor_header *)&ac_interface_desc,
        (struct usb_descriptor_header *)&ac_header_desc,

        (struct usb_descriptor_header *)&usb_out_it_desc,
        (struct usb_descriptor_header *)&io_out_ot_desc,
        (struct usb_descriptor_header *)&io_in_it_desc,
        (struct usb_descriptor_header *)&usb_in_ot_desc,

        (struct usb_descriptor_header *)&as_out_interface_alt_0_desc,
        (struct usb_descriptor_header *)&as_out_interface_alt_1_desc,
        (struct usb_descriptor_header *)&as_out_header_desc,

        (struct usb_descriptor_header *)&as_out_type_i_desc,

        //(struct usb_descriptor_header *)&as_out_ep_desc,
        (struct usb_descriptor_header *)&ss_as_out_ep_desc,
        (struct usb_descriptor_header *)&ss_as_out_ep_desc_comp,
        (struct usb_descriptor_header *)&as_iso_out_desc,

        (struct usb_descriptor_header *)&as_in_interface_alt_0_desc,
        (struct usb_descriptor_header *)&as_in_interface_alt_1_desc,
        (struct usb_descriptor_header *)&as_in_header_desc,

        (struct usb_descriptor_header *)&as_in_type_i_desc,

        //(struct usb_descriptor_header *)&as_in_ep_desc,
        (struct usb_descriptor_header *)&ss_as_in_ep_desc,
        (struct usb_descriptor_header *)&ss_as_in_ep_desc_comp,
        (struct usb_descriptor_header *)&as_iso_in_desc,
        NULL,
};

enum {
        STR_AC_IF,
        STR_USB_OUT_IT,
        STR_USB_OUT_IT_CH_NAMES,
        STR_IO_OUT_OT,
        STR_IO_IN_IT,
        STR_IO_IN_IT_CH_NAMES,
        STR_USB_IN_OT,
        STR_FU_IN,
        STR_FU_OUT,
        STR_AS_OUT_IF_ALT0,
        STR_AS_OUT_IF_ALT1,
        STR_AS_IN_IF_ALT0,
        STR_AS_IN_IF_ALT1,
        NUM_STR_DESCRIPTORS,
};

static struct usb_string strings_uac1[NUM_STR_DESCRIPTORS + 1] = {};

static struct usb_gadget_strings str_uac1 = {
        .language = 0x0409,     /* en-us */
        .strings = strings_uac1,
};

static struct usb_gadget_strings *uac1_strings[] = {
        &str_uac1,
        NULL,
};

/*
 * This function is an ALSA sound card following USB Audio Class Spec 1.0.
 */

static void uac_cs_attr_sample_rate(struct usb_ep *ep, struct usb_request *req)
{
        struct usb_function *fn = ep->driver_data;
        struct usb_composite_dev *cdev = fn->config->cdev;
        struct g_audio *agdev = func_to_g_audio(fn);
        struct f_uac1 *uac1 = func_to_uac1(fn);
        u8 *buf = (u8 *)req->buf;
        u32 val = 0;

        if (req->actual != 3) {
                WARN(cdev, "Invalid data size for UAC_EP_CS_ATTR_SAMPLE_RATE.\n");
                return;
        }

        val = buf[0] | (buf[1] << 8) | (buf[2] << 16);
        if (uac1->ctl_id == (USB_DIR_IN | 2)) {
                uac1->p_srate = val;
                u_audio_set_playback_srate(agdev, uac1->p_srate);
        } else if (uac1->ctl_id == (USB_DIR_OUT | 1)) {
                uac1->c_srate = val;
                u_audio_set_capture_srate(agdev, uac1->c_srate);
        }
}

static void audio_notify_complete(struct usb_ep *_ep, struct usb_request *req)
{
        struct g_audio *audio = req->context;
        struct f_uac1 *uac1 = func_to_uac1(&audio->func);

        atomic_dec(&uac1->int_count);
        kfree(req->buf);
        usb_ep_free_request(_ep, req);
}

static int audio_notify(struct g_audio *audio, int unit_id, int cs)
{
        struct f_uac1 *uac1 = func_to_uac1(&audio->func);
        struct usb_request *req;
        struct uac1_status_word *msg;
        int ret;

        if (!uac1->int_ep->enabled)
                return 0;

        if (atomic_inc_return(&uac1->int_count) > UAC1_DEF_INT_REQ_NUM) {
                atomic_dec(&uac1->int_count);
                return 0;
        }

        req = usb_ep_alloc_request(uac1->int_ep, GFP_ATOMIC);
        if (req == NULL) {
                ret = -ENOMEM;
                goto err_dec_int_count;
        }

        msg = kmalloc_obj(*msg, GFP_ATOMIC);
        if (msg == NULL) {
                ret = -ENOMEM;
                goto err_free_request;
        }

        msg->bStatusType = UAC1_STATUS_TYPE_IRQ_PENDING
                                | UAC1_STATUS_TYPE_ORIG_AUDIO_CONTROL_IF;
        msg->bOriginator = unit_id;

        req->length = sizeof(*msg);
        req->buf = msg;
        req->context = audio;
        req->complete = audio_notify_complete;

        ret = usb_ep_queue(uac1->int_ep, req, GFP_ATOMIC);

        if (ret)
                goto err_free_msg;

        return 0;

err_free_msg:
        kfree(msg);
err_free_request:
        usb_ep_free_request(uac1->int_ep, req);
err_dec_int_count:
        atomic_dec(&uac1->int_count);

        return ret;
}

static int
in_rq_cur(struct usb_function *fn, const struct usb_ctrlrequest *cr)
{
        struct usb_request *req = fn->config->cdev->req;
        struct g_audio *audio = func_to_g_audio(fn);
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        u16 w_length = le16_to_cpu(cr->wLength);
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;
        int value = -EOPNOTSUPP;

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                unsigned int is_playback = 0;

                if (FUIN_EN(opts) && (entity_id == USB_IN_FU_ID))
                        is_playback = 1;

                if (control_selector == UAC_FU_MUTE) {
                        unsigned int mute;

                        u_audio_get_mute(audio, is_playback, &mute);

                        *(u8 *)req->buf = mute;
                        value = min_t(unsigned int, w_length, 1);
                } else if (control_selector == UAC_FU_VOLUME) {
                        __le16 c;
                        s16 volume;

                        u_audio_get_volume(audio, is_playback, &volume);

                        c = cpu_to_le16(volume);

                        value = min_t(unsigned int, w_length, sizeof(c));
                        memcpy(req->buf, &c, value);
                } else {
                        dev_err(&audio->gadget->dev,
                                "%s:%d control_selector=%d TODO!\n",
                                __func__, __LINE__, control_selector);
                }
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
        }

        return value;
}

static int
in_rq_min(struct usb_function *fn, const struct usb_ctrlrequest *cr)
{
        struct usb_request *req = fn->config->cdev->req;
        struct g_audio *audio = func_to_g_audio(fn);
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        u16 w_length = le16_to_cpu(cr->wLength);
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;
        int value = -EOPNOTSUPP;

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                unsigned int is_playback = 0;

                if (FUIN_EN(opts) && (entity_id == USB_IN_FU_ID))
                        is_playback = 1;

                if (control_selector == UAC_FU_VOLUME) {
                        __le16 r;
                        s16 min_db;

                        if (is_playback)
                                min_db = opts->p_volume_min;
                        else
                                min_db = opts->c_volume_min;

                        r = cpu_to_le16(min_db);

                        value = min_t(unsigned int, w_length, sizeof(r));
                        memcpy(req->buf, &r, value);
                } else {
                        dev_err(&audio->gadget->dev,
                                "%s:%d control_selector=%d TODO!\n",
                                __func__, __LINE__, control_selector);
                }
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
        }

        return value;
}

static int
in_rq_max(struct usb_function *fn, const struct usb_ctrlrequest *cr)
{
        struct usb_request *req = fn->config->cdev->req;
        struct g_audio *audio = func_to_g_audio(fn);
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        u16 w_length = le16_to_cpu(cr->wLength);
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;
        int value = -EOPNOTSUPP;

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                unsigned int is_playback = 0;

                if (FUIN_EN(opts) && (entity_id == USB_IN_FU_ID))
                        is_playback = 1;

                if (control_selector == UAC_FU_VOLUME) {
                        __le16 r;
                        s16 max_db;

                        if (is_playback)
                                max_db = opts->p_volume_max;
                        else
                                max_db = opts->c_volume_max;

                        r = cpu_to_le16(max_db);

                        value = min_t(unsigned int, w_length, sizeof(r));
                        memcpy(req->buf, &r, value);
                } else {
                        dev_err(&audio->gadget->dev,
                                "%s:%d control_selector=%d TODO!\n",
                                __func__, __LINE__, control_selector);
                }
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
        }

        return value;
}

static int
in_rq_res(struct usb_function *fn, const struct usb_ctrlrequest *cr)
{
        struct usb_request *req = fn->config->cdev->req;
        struct g_audio *audio = func_to_g_audio(fn);
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        u16 w_length = le16_to_cpu(cr->wLength);
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;
        int value = -EOPNOTSUPP;

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                unsigned int is_playback = 0;

                if (FUIN_EN(opts) && (entity_id == USB_IN_FU_ID))
                        is_playback = 1;

                if (control_selector == UAC_FU_VOLUME) {
                        __le16 r;
                        s16 res_db;

                        if (is_playback)
                                res_db = opts->p_volume_res;
                        else
                                res_db = opts->c_volume_res;

                        r = cpu_to_le16(res_db);

                        value = min_t(unsigned int, w_length, sizeof(r));
                        memcpy(req->buf, &r, value);
                } else {
                        dev_err(&audio->gadget->dev,
                                "%s:%d control_selector=%d TODO!\n",
                                __func__, __LINE__, control_selector);
                }
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
        }

        return value;
}

static void
out_rq_cur_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct g_audio *audio = req->context;
        struct usb_composite_dev *cdev = audio->func.config->cdev;
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        struct f_uac1 *uac1 = func_to_uac1(&audio->func);
        struct usb_ctrlrequest *cr = &uac1->setup_cr;
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;

        if (req->status != 0) {
                dev_dbg(&cdev->gadget->dev, "completion err %d\n", req->status);
                return;
        }

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                unsigned int is_playback = 0;

                if (FUIN_EN(opts) && (entity_id == USB_IN_FU_ID))
                        is_playback = 1;

                if (control_selector == UAC_FU_MUTE) {
                        u8 mute = *(u8 *)req->buf;

                        u_audio_set_mute(audio, is_playback, mute);

                        return;
                } else if (control_selector == UAC_FU_VOLUME) {
                        __le16 *c = req->buf;
                        s16 volume;

                        volume = le16_to_cpu(*c);
                        u_audio_set_volume(audio, is_playback, volume);

                        return;
                } else {
                        dev_err(&audio->gadget->dev,
                                "%s:%d control_selector=%d TODO!\n",
                                __func__, __LINE__, control_selector);
                        usb_ep_set_halt(ep);
                }
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
                usb_ep_set_halt(ep);

        }
}

static int
out_rq_cur(struct usb_function *fn, const struct usb_ctrlrequest *cr)
{
        struct usb_request *req = fn->config->cdev->req;
        struct g_audio *audio = func_to_g_audio(fn);
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);
        struct f_uac1 *uac1 = func_to_uac1(&audio->func);
        u16 w_length = le16_to_cpu(cr->wLength);
        u16 w_index = le16_to_cpu(cr->wIndex);
        u16 w_value = le16_to_cpu(cr->wValue);
        u8 entity_id = (w_index >> 8) & 0xff;
        u8 control_selector = w_value >> 8;

        if ((FUIN_EN(opts) && (entity_id == USB_IN_FU_ID)) ||
                        (FUOUT_EN(opts) && (entity_id == USB_OUT_FU_ID))) {
                memcpy(&uac1->setup_cr, cr, sizeof(*cr));
                req->context = audio;
                req->complete = out_rq_cur_complete;

                return w_length;
        } else {
                dev_err(&audio->gadget->dev,
                        "%s:%d entity_id=%d control_selector=%d TODO!\n",
                        __func__, __LINE__, entity_id, control_selector);
        }
        return -EOPNOTSUPP;
}

static int ac_rq_in(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:
                return in_rq_cur(f, ctrl);
        case UAC_GET_MIN:
                return in_rq_min(f, ctrl);
        case UAC_GET_MAX:
                return in_rq_max(f, ctrl);
        case UAC_GET_RES:
                return in_rq_res(f, ctrl);
        case UAC_GET_MEM:
                break;
        case UAC_GET_STAT:
                value = len;
                break;
        default:
                break;
        }

        return value;
}

static int audio_set_endpoint_req(struct usb_function *f,
                const struct usb_ctrlrequest *ctrl)
{
        struct usb_composite_dev *cdev = f->config->cdev;
        struct usb_request      *req = f->config->cdev->req;
        struct f_uac1           *uac1 = func_to_uac1(f);
        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);
        u8                      cs = w_value >> 8;

        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: {
                if (cs == UAC_EP_CS_ATTR_SAMPLE_RATE) {
                        cdev->gadget->ep0->driver_data = f;
                        uac1->ctl_id = ep;
                        req->complete = uac_cs_attr_sample_rate;
                }
                value = len;
                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;
        struct usb_request *req = f->config->cdev->req;
        struct f_uac1 *uac1 = func_to_uac1(f);
        u8 *buf = (u8 *)req->buf;
        int value = -EOPNOTSUPP;
        u8 ep = le16_to_cpu(ctrl->wIndex);
        u16 len = le16_to_cpu(ctrl->wLength);
        u16 w_value = le16_to_cpu(ctrl->wValue);
        u8 cs = w_value >> 8;
        u32 val = 0;

        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: {
                if (cs == UAC_EP_CS_ATTR_SAMPLE_RATE) {
                        if (ep == (USB_DIR_IN | 2))
                                val = uac1->p_srate;
                        else if (ep == (USB_DIR_OUT | 1))
                                val = uac1->c_srate;
                        buf[2] = (val >> 16) & 0xff;
                        buf[1] = (val >> 8) & 0xff;
                        buf[0] = val & 0xff;
                }
                value = len;
                break;
        }
        case UAC_GET_MIN:
        case UAC_GET_MAX:
        case UAC_GET_RES:
                value = len;
                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_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;
        case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
                if (ctrl->bRequest == UAC_SET_CUR)
                        value = out_rq_cur(f, ctrl);
                break;
        case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE:
                value = ac_rq_in(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 usb_composite_dev *cdev = f->config->cdev;
        struct usb_gadget *gadget = cdev->gadget;
        struct device *dev = &gadget->dev;
        struct g_audio *audio = func_to_g_audio(f);
        struct f_uac1 *uac1 = func_to_uac1(f);
        int ret = 0;

        /* No i/f has more than 2 alt settings */
        if (alt > 1) {
                dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
                return -EINVAL;
        }

        if (intf == uac1->ac_intf) {
                /* Control I/f has only 1 AltSetting - 0 */
                if (alt) {
                        dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
                        return -EINVAL;
                }

                /* restart interrupt endpoint */
                if (uac1->int_ep) {
                        usb_ep_disable(uac1->int_ep);
                        config_ep_by_speed(gadget, &audio->func, uac1->int_ep);
                        usb_ep_enable(uac1->int_ep);
                }

                return 0;
        }

        if (intf == uac1->as_out_intf) {
                uac1->as_out_alt = alt;

                if (alt)
                        ret = u_audio_start_capture(&uac1->g_audio);
                else
                        u_audio_stop_capture(&uac1->g_audio);
        } else if (intf == uac1->as_in_intf) {
                uac1->as_in_alt = alt;

                if (alt)
                        ret = u_audio_start_playback(&uac1->g_audio);
                else
                        u_audio_stop_playback(&uac1->g_audio);
        } else {
                dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
                return -EINVAL;
        }

        return ret;
}

static int f_audio_get_alt(struct usb_function *f, unsigned intf)
{
        struct usb_composite_dev *cdev = f->config->cdev;
        struct usb_gadget *gadget = cdev->gadget;
        struct device *dev = &gadget->dev;
        struct f_uac1 *uac1 = func_to_uac1(f);

        if (intf == uac1->ac_intf)
                return uac1->ac_alt;
        else if (intf == uac1->as_out_intf)
                return uac1->as_out_alt;
        else if (intf == uac1->as_in_intf)
                return uac1->as_in_alt;
        else
                dev_err(dev, "%s:%d Invalid Interface %d!\n",
                        __func__, __LINE__, intf);

        return -EINVAL;
}


static void f_audio_disable(struct usb_function *f)
{
        struct f_uac1 *uac1 = func_to_uac1(f);

        uac1->as_out_alt = 0;
        uac1->as_in_alt = 0;

        u_audio_stop_playback(&uac1->g_audio);
        u_audio_stop_capture(&uac1->g_audio);
        if (uac1->int_ep)
                usb_ep_disable(uac1->int_ep);
}

static void
f_audio_suspend(struct usb_function *f)
{
        struct f_uac1 *uac1 = func_to_uac1(f);

        u_audio_suspend(&uac1->g_audio);
}

/*-------------------------------------------------------------------------*/
static struct uac_feature_unit_descriptor *build_fu_desc(int chmask)
{
        struct uac_feature_unit_descriptor *fu_desc;
        int channels = num_channels(chmask);
        int fu_desc_size = UAC_DT_FEATURE_UNIT_SIZE(channels);

        fu_desc = kzalloc(fu_desc_size, GFP_KERNEL);
        if (!fu_desc)
                return NULL;

        fu_desc->bLength = fu_desc_size;
        fu_desc->bDescriptorType = USB_DT_CS_INTERFACE;

        fu_desc->bDescriptorSubtype = UAC_FEATURE_UNIT;
        fu_desc->bControlSize  = 2;

        /* bUnitID, bSourceID and bmaControls will be defined later */

        return fu_desc;
}

/* B.3.2  Class-Specific AC Interface Descriptor */
static struct
uac1_ac_header_descriptor *build_ac_header_desc(struct f_uac1_opts *opts)
{
        struct uac1_ac_header_descriptor *ac_desc;
        int ac_header_desc_size;
        int num_ifaces = 0;

        if (EPOUT_EN(opts))
                num_ifaces++;
        if (EPIN_EN(opts))
                num_ifaces++;

        ac_header_desc_size = UAC_DT_AC_HEADER_SIZE(num_ifaces);

        ac_desc = kzalloc(ac_header_desc_size, GFP_KERNEL);
        if (!ac_desc)
                return NULL;

        ac_desc->bLength = ac_header_desc_size;
        ac_desc->bDescriptorType = USB_DT_CS_INTERFACE;
        ac_desc->bDescriptorSubtype = UAC_HEADER;
        ac_desc->bcdADC = cpu_to_le16(0x0100);
        ac_desc->bInCollection = num_ifaces;

        /* wTotalLength and baInterfaceNr will be defined later */

        return ac_desc;
}

/* Use macro to overcome line length limitation */
#define USBDHDR(p) (struct usb_descriptor_header *)(p)

static void setup_descriptor(struct f_uac1_opts *opts)
{
        /* patch descriptors */
        int i = 1; /* ID's start with 1 */

        if (EPOUT_EN(opts))
                usb_out_it_desc.bTerminalID = i++;
        if (EPIN_EN(opts))
                io_in_it_desc.bTerminalID = i++;
        if (EPOUT_EN(opts))
                io_out_ot_desc.bTerminalID = i++;
        if (EPIN_EN(opts))
                usb_in_ot_desc.bTerminalID = i++;
        if (FUOUT_EN(opts))
                out_feature_unit_desc->bUnitID = i++;
        if (FUIN_EN(opts))
                in_feature_unit_desc->bUnitID = i++;

        if (FUIN_EN(opts)) {
                usb_in_ot_desc.bSourceID = in_feature_unit_desc->bUnitID;
                in_feature_unit_desc->bSourceID = io_in_it_desc.bTerminalID;
        } else {
                usb_in_ot_desc.bSourceID = io_in_it_desc.bTerminalID;
        }
        if (FUOUT_EN(opts)) {
                io_out_ot_desc.bSourceID = out_feature_unit_desc->bUnitID;
                out_feature_unit_desc->bSourceID = usb_out_it_desc.bTerminalID;
        } else {
                io_out_ot_desc.bSourceID = usb_out_it_desc.bTerminalID;
        }

        as_out_header_desc.bTerminalLink = usb_out_it_desc.bTerminalID;
        as_in_header_desc.bTerminalLink = usb_in_ot_desc.bTerminalID;

        ac_header_desc->wTotalLength = cpu_to_le16(ac_header_desc->bLength);

        if (EPIN_EN(opts)) {
                u16 len = le16_to_cpu(ac_header_desc->wTotalLength);

                len += sizeof(usb_in_ot_desc);
                len += sizeof(io_in_it_desc);
                if (FUIN_EN(opts))
                        len += in_feature_unit_desc->bLength;
                ac_header_desc->wTotalLength = cpu_to_le16(len);
        }
        if (EPOUT_EN(opts)) {
                u16 len = le16_to_cpu(ac_header_desc->wTotalLength);

                len += sizeof(usb_out_it_desc);
                len += sizeof(io_out_ot_desc);
                if (FUOUT_EN(opts))
                        len += out_feature_unit_desc->bLength;
                ac_header_desc->wTotalLength = cpu_to_le16(len);
        }

        i = 0;
        f_audio_desc[i++] = USBDHDR(&ac_interface_desc);
        f_audio_desc[i++] = USBDHDR(ac_header_desc);

        if (EPOUT_EN(opts)) {
                f_audio_desc[i++] = USBDHDR(&usb_out_it_desc);
                f_audio_desc[i++] = USBDHDR(&io_out_ot_desc);
                if (FUOUT_EN(opts))
                        f_audio_desc[i++] = USBDHDR(out_feature_unit_desc);
        }

        if (EPIN_EN(opts)) {
                f_audio_desc[i++] = USBDHDR(&io_in_it_desc);
                f_audio_desc[i++] = USBDHDR(&usb_in_ot_desc);
                if (FUIN_EN(opts))
                        f_audio_desc[i++] = USBDHDR(in_feature_unit_desc);
        }

        if (FUOUT_EN(opts) || FUIN_EN(opts))
                f_audio_desc[i++] = USBDHDR(&ac_int_ep_desc);

        if (EPOUT_EN(opts)) {
                f_audio_desc[i++] = USBDHDR(&as_out_interface_alt_0_desc);
                f_audio_desc[i++] = USBDHDR(&as_out_interface_alt_1_desc);
                f_audio_desc[i++] = USBDHDR(&as_out_header_desc);
                f_audio_desc[i++] = USBDHDR(&as_out_type_i_desc);
                f_audio_desc[i++] = USBDHDR(&as_out_ep_desc);
                f_audio_desc[i++] = USBDHDR(&as_iso_out_desc);
        }
        if (EPIN_EN(opts)) {
                f_audio_desc[i++] = USBDHDR(&as_in_interface_alt_0_desc);
                f_audio_desc[i++] = USBDHDR(&as_in_interface_alt_1_desc);
                f_audio_desc[i++] = USBDHDR(&as_in_header_desc);
                f_audio_desc[i++] = USBDHDR(&as_in_type_i_desc);
                f_audio_desc[i++] = USBDHDR(&as_in_ep_desc);
                f_audio_desc[i++] = USBDHDR(&as_iso_in_desc);
        }
        f_audio_desc[i] = NULL;
}

static int f_audio_validate_opts(struct g_audio *audio, struct device *dev)
{
        struct f_uac1_opts *opts = g_audio_to_uac1_opts(audio);

        if (!opts->p_chmask && !opts->c_chmask) {
                dev_err(dev, "Error: no playback and capture channels\n");
                return -EINVAL;
        } else if (opts->p_chmask & ~UAC1_CHANNEL_MASK) {
                dev_err(dev, "Error: unsupported playback channels mask\n");
                return -EINVAL;
        } else if (opts->c_chmask & ~UAC1_CHANNEL_MASK) {
                dev_err(dev, "Error: unsupported capture channels mask\n");
                return -EINVAL;
        } else if ((opts->p_ssize < 1) || (opts->p_ssize > 4)) {
                dev_err(dev, "Error: incorrect playback sample size\n");
                return -EINVAL;
        } else if ((opts->c_ssize < 1) || (opts->c_ssize > 4)) {
                dev_err(dev, "Error: incorrect capture sample size\n");
                return -EINVAL;
        } else if (!opts->p_srates[0]) {
                dev_err(dev, "Error: incorrect playback sampling rate\n");
                return -EINVAL;
        } else if (!opts->c_srates[0]) {
                dev_err(dev, "Error: incorrect capture sampling rate\n");
                return -EINVAL;
        }

        if (opts->p_volume_max <= opts->p_volume_min) {
                dev_err(dev, "Error: incorrect playback volume max/min\n");
                return -EINVAL;
        } else if (opts->c_volume_max <= opts->c_volume_min) {
                dev_err(dev, "Error: incorrect capture volume max/min\n");
                return -EINVAL;
        } else if (opts->p_volume_res <= 0) {
                dev_err(dev, "Error: negative/zero playback volume resolution\n");
                return -EINVAL;
        } else if (opts->c_volume_res <= 0) {
                dev_err(dev, "Error: negative/zero capture volume resolution\n");
                return -EINVAL;
        }

        if ((opts->p_volume_max - opts->p_volume_min) % opts->p_volume_res) {
                dev_err(dev, "Error: incorrect playback volume resolution\n");
                return -EINVAL;
        } else if ((opts->c_volume_max - opts->c_volume_min) % opts->c_volume_res) {
                dev_err(dev, "Error: incorrect capture volume resolution\n");
                return -EINVAL;
        }

        return 0;
}

/* audio function driver setup/binding */
static int f_audio_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev        *cdev = c->cdev;
        struct usb_gadget               *gadget = cdev->gadget;
        struct device                   *dev = &gadget->dev;
        struct f_uac1                   *uac1 = func_to_uac1(f);
        struct g_audio                  *audio = func_to_g_audio(f);
        struct f_uac1_opts              *audio_opts;
        struct usb_ep                   *ep = NULL;
        struct usb_string               *us;
        int                             ba_iface_id;
        int                             status;
        int                             idx, i;

        status = f_audio_validate_opts(audio, dev);
        if (status)
                return status;

        audio_opts = container_of(f->fi, struct f_uac1_opts, func_inst);

        strings_uac1[STR_AC_IF].s = audio_opts->function_name;

        strings_uac1[STR_USB_OUT_IT].s = audio_opts->c_it_name;
        strings_uac1[STR_USB_OUT_IT_CH_NAMES].s = audio_opts->c_it_ch_name;
        strings_uac1[STR_IO_OUT_OT].s = audio_opts->c_ot_name;
        strings_uac1[STR_FU_OUT].s = audio_opts->c_fu_vol_name;
        strings_uac1[STR_AS_OUT_IF_ALT0].s = "Playback Inactive";
        strings_uac1[STR_AS_OUT_IF_ALT1].s = "Playback Active";

        strings_uac1[STR_IO_IN_IT].s = audio_opts->p_it_name;
        strings_uac1[STR_IO_IN_IT_CH_NAMES].s = audio_opts->p_it_ch_name;
        strings_uac1[STR_USB_IN_OT].s = audio_opts->p_ot_name;
        strings_uac1[STR_FU_IN].s = audio_opts->p_fu_vol_name;
        strings_uac1[STR_AS_IN_IF_ALT0].s = "Capture Inactive";
        strings_uac1[STR_AS_IN_IF_ALT1].s = "Capture Active";

        us = usb_gstrings_attach(cdev, uac1_strings, ARRAY_SIZE(strings_uac1));
        if (IS_ERR(us))
                return PTR_ERR(us);

        ac_header_desc = build_ac_header_desc(audio_opts);
        if (!ac_header_desc)
                return -ENOMEM;

        if (FUOUT_EN(audio_opts)) {
                out_feature_unit_desc = build_fu_desc(audio_opts->c_chmask);
                if (!out_feature_unit_desc) {
                        status = -ENOMEM;
                        goto fail;
                }
        }
        if (FUIN_EN(audio_opts)) {
                in_feature_unit_desc = build_fu_desc(audio_opts->p_chmask);
                if (!in_feature_unit_desc) {
                        status = -ENOMEM;
                        goto err_free_fu;
                }
        }

        ac_interface_desc.iInterface = us[STR_AC_IF].id;
        usb_out_it_desc.iTerminal = us[STR_USB_OUT_IT].id;
        usb_out_it_desc.iChannelNames = us[STR_USB_OUT_IT_CH_NAMES].id;
        io_out_ot_desc.iTerminal = us[STR_IO_OUT_OT].id;
        as_out_interface_alt_0_desc.iInterface = us[STR_AS_OUT_IF_ALT0].id;
        as_out_interface_alt_1_desc.iInterface = us[STR_AS_OUT_IF_ALT1].id;
        io_in_it_desc.iTerminal = us[STR_IO_IN_IT].id;
        io_in_it_desc.iChannelNames = us[STR_IO_IN_IT_CH_NAMES].id;
        usb_in_ot_desc.iTerminal = us[STR_USB_IN_OT].id;
        as_in_interface_alt_0_desc.iInterface = us[STR_AS_IN_IF_ALT0].id;
        as_in_interface_alt_1_desc.iInterface = us[STR_AS_IN_IF_ALT1].id;

        if (FUOUT_EN(audio_opts)) {
                u8 *i_feature;

                i_feature = (u8 *)out_feature_unit_desc +
                                        out_feature_unit_desc->bLength - 1;
                *i_feature = us[STR_FU_OUT].id;
        }
        if (FUIN_EN(audio_opts)) {
                u8 *i_feature;

                i_feature = (u8 *)in_feature_unit_desc +
                                        in_feature_unit_desc->bLength - 1;
                *i_feature = us[STR_FU_IN].id;
        }

        /* Set channel numbers */
        usb_out_it_desc.bNrChannels = num_channels(audio_opts->c_chmask);
        usb_out_it_desc.wChannelConfig = cpu_to_le16(audio_opts->c_chmask);
        as_out_type_i_desc.bNrChannels = num_channels(audio_opts->c_chmask);
        as_out_type_i_desc.bSubframeSize = audio_opts->c_ssize;
        as_out_type_i_desc.bBitResolution = audio_opts->c_ssize * 8;
        io_in_it_desc.bNrChannels = num_channels(audio_opts->p_chmask);
        io_in_it_desc.wChannelConfig = cpu_to_le16(audio_opts->p_chmask);
        as_in_type_i_desc.bNrChannels = num_channels(audio_opts->p_chmask);
        as_in_type_i_desc.bSubframeSize = audio_opts->p_ssize;
        as_in_type_i_desc.bBitResolution = audio_opts->p_ssize * 8;

        if (FUOUT_EN(audio_opts)) {
                __le16 *bma = (__le16 *)&out_feature_unit_desc->bmaControls[0];
                u32 control = 0;

                if (audio_opts->c_mute_present)
                        control |= UAC_FU_MUTE;
                if (audio_opts->c_volume_present)
                        control |= UAC_FU_VOLUME;
                *bma = cpu_to_le16(control);
        }
        if (FUIN_EN(audio_opts)) {
                __le16 *bma = (__le16 *)&in_feature_unit_desc->bmaControls[0];
                u32 control = 0;

                if (audio_opts->p_mute_present)
                        control |= UAC_FU_MUTE;
                if (audio_opts->p_volume_present)
                        control |= UAC_FU_VOLUME;
                *bma = cpu_to_le16(control);
        }

        /* Set sample rates */
        for (i = 0, idx = 0; i < UAC_MAX_RATES; i++) {
                if (audio_opts->c_srates[i] == 0)
                        break;
                memcpy(as_out_type_i_desc.tSamFreq[idx++],
                                &audio_opts->c_srates[i], 3);
        }
        as_out_type_i_desc.bLength = UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(idx);
        as_out_type_i_desc.bSamFreqType = idx;

        for (i = 0, idx = 0; i < UAC_MAX_RATES; i++) {
                if (audio_opts->p_srates[i] == 0)
                        break;
                memcpy(as_in_type_i_desc.tSamFreq[idx++],
                                &audio_opts->p_srates[i], 3);
        }
        as_in_type_i_desc.bLength = UAC_FORMAT_TYPE_I_DISCRETE_DESC_SIZE(idx);
        as_in_type_i_desc.bSamFreqType = idx;
        uac1->p_srate = audio_opts->p_srates[0];
        uac1->c_srate = audio_opts->c_srates[0];

        /* allocate instance-specific interface IDs, and patch descriptors */
        status = usb_interface_id(c, f);
        if (status < 0)
                goto err_free_fu;
        ac_interface_desc.bInterfaceNumber = status;
        uac1->ac_intf = status;
        uac1->ac_alt = 0;

        ba_iface_id = 0;

        if (EPOUT_EN(audio_opts)) {
                status = usb_interface_id(c, f);
                if (status < 0)
                        goto err_free_fu;
                as_out_interface_alt_0_desc.bInterfaceNumber = status;
                as_out_interface_alt_1_desc.bInterfaceNumber = status;
                ac_header_desc->baInterfaceNr[ba_iface_id++] = status;
                uac1->as_out_intf = status;
                uac1->as_out_alt = 0;
        }

        if (EPIN_EN(audio_opts)) {
                status = usb_interface_id(c, f);
                if (status < 0)
                        goto err_free_fu;
                as_in_interface_alt_0_desc.bInterfaceNumber = status;
                as_in_interface_alt_1_desc.bInterfaceNumber = status;
                ac_header_desc->baInterfaceNr[ba_iface_id++] = status;
                uac1->as_in_intf = status;
                uac1->as_in_alt = 0;
        }

        audio->gadget = gadget;

        status = -ENODEV;

        ac_interface_desc.bNumEndpoints = 0;

        /* allocate AC interrupt endpoint */
        if (FUOUT_EN(audio_opts) || FUIN_EN(audio_opts)) {
                ep = usb_ep_autoconfig(cdev->gadget, &ac_int_ep_desc);
                if (!ep)
                        goto err_free_fu;
                uac1->int_ep = ep;
                uac1->int_ep->desc = &ac_int_ep_desc;

                ac_interface_desc.bNumEndpoints = 1;
        }

        /* allocate instance-specific endpoints */
        if (EPOUT_EN(audio_opts)) {
                ep = usb_ep_autoconfig(cdev->gadget, &as_out_ep_desc);
                if (!ep)
                        goto err_free_fu;
                ss_as_out_ep_desc.bEndpointAddress = as_out_ep_desc.bEndpointAddress;
                audio->out_ep = ep;
                audio->out_ep->desc = &as_out_ep_desc;
        }

        if (EPIN_EN(audio_opts)) {
                ep = usb_ep_autoconfig(cdev->gadget, &as_in_ep_desc);
                if (!ep)
                        goto err_free_fu;
                ss_as_in_ep_desc.bEndpointAddress = as_in_ep_desc.bEndpointAddress;
                audio->in_ep = ep;
                audio->in_ep->desc = &as_in_ep_desc;
        }

        setup_descriptor(audio_opts);

        /* copy descriptors, and track endpoint copies */
        status = usb_assign_descriptors(f, f_audio_desc, f_audio_desc, f_audio_ss_desc,
                                        f_audio_ss_desc);
        if (status)
                goto err_free_fu;

        audio->out_ep_maxpsize = le16_to_cpu(as_out_ep_desc.wMaxPacketSize);
        audio->in_ep_maxpsize = le16_to_cpu(as_in_ep_desc.wMaxPacketSize);
        audio->params.c_chmask = audio_opts->c_chmask;
        memcpy(audio->params.c_srates, audio_opts->c_srates,
                        sizeof(audio->params.c_srates));
        audio->params.c_ssize = audio_opts->c_ssize;
        if (FUIN_EN(audio_opts)) {
                audio->params.p_fu.id = USB_IN_FU_ID;
                audio->params.p_fu.mute_present = audio_opts->p_mute_present;
                audio->params.p_fu.volume_present =
                                audio_opts->p_volume_present;
                audio->params.p_fu.volume_min = audio_opts->p_volume_min;
                audio->params.p_fu.volume_max = audio_opts->p_volume_max;
                audio->params.p_fu.volume_res = audio_opts->p_volume_res;
        }
        audio->params.p_chmask = audio_opts->p_chmask;
        memcpy(audio->params.p_srates, audio_opts->p_srates,
                        sizeof(audio->params.p_srates));
        audio->params.p_ssize = audio_opts->p_ssize;
        if (FUOUT_EN(audio_opts)) {
                audio->params.c_fu.id = USB_OUT_FU_ID;
                audio->params.c_fu.mute_present = audio_opts->c_mute_present;
                audio->params.c_fu.volume_present =
                                audio_opts->c_volume_present;
                audio->params.c_fu.volume_min = audio_opts->c_volume_min;
                audio->params.c_fu.volume_max = audio_opts->c_volume_max;
                audio->params.c_fu.volume_res = audio_opts->c_volume_res;
        }
        audio->params.req_number = audio_opts->req_number;
        audio->params.fb_max = FBACK_FAST_MAX;
        if (FUOUT_EN(audio_opts) || FUIN_EN(audio_opts))
                audio->notify = audio_notify;

        status = g_audio_setup(audio, "UAC1_PCM", "UAC1_Gadget");
        if (status)
                goto err_card_register;

        return 0;

err_card_register:
        usb_free_all_descriptors(f);
err_free_fu:
        kfree(out_feature_unit_desc);
        out_feature_unit_desc = NULL;
        kfree(in_feature_unit_desc);
        in_feature_unit_desc = NULL;
fail:
        kfree(ac_header_desc);
        ac_header_desc = NULL;
        return status;
}

/*-------------------------------------------------------------------------*/

static inline struct f_uac1_opts *to_f_uac1_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct f_uac1_opts,
                            func_inst.group);
}

static void f_uac1_attr_release(struct config_item *item)
{
        struct f_uac1_opts *opts = to_f_uac1_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static const struct configfs_item_operations f_uac1_item_ops = {
        .release        = f_uac1_attr_release,
};

#define uac1_kstrtou32                  kstrtou32
#define uac1_kstrtos16                  kstrtos16
#define uac1_kstrtobool(s, base, res)   kstrtobool((s), (res))

static const char *u32_fmt = "%u\n";
static const char *s16_fmt = "%hd\n";
static const char *bool_fmt = "%u\n";

#define UAC1_ATTRIBUTE(type, name)                                      \
static ssize_t f_uac1_opts_##name##_show(                               \
                                          struct config_item *item,     \
                                          char *page)                   \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        result = sprintf(page, type##_fmt, opts->name);                 \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_uac1_opts_##name##_store(                              \
                                          struct config_item *item,     \
                                          const char *page, size_t len) \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        int ret;                                                        \
        type num;                                                       \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt) {                                             \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        ret = uac1_kstrto##type(page, 0, &num);                         \
        if (ret)                                                        \
                goto end;                                               \
                                                                        \
        opts->name = num;                                               \
        ret = len;                                                      \
                                                                        \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_uac1_opts_, name)

#define UAC1_RATE_ATTRIBUTE(name)                                       \
static ssize_t f_uac1_opts_##name##_show(struct config_item *item,      \
                                         char *page)                    \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        int result = 0;                                                 \
        int i;                                                          \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        page[0] = '\0';                                                 \
        for (i = 0; i < UAC_MAX_RATES; i++) {                           \
                if (opts->name##s[i] == 0)                              \
                        break;                                          \
                result += sprintf(page + strlen(page), "%u,",           \
                                opts->name##s[i]);                      \
        }                                                               \
        if (strlen(page) > 0)                                           \
                page[strlen(page) - 1] = '\n';                          \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_uac1_opts_##name##_store(struct config_item *item,     \
                                          const char *page, size_t len) \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        char *split_page = NULL;                                        \
        int ret = -EINVAL;                                              \
        char *token;                                                    \
        u32 num;                                                        \
        int i;                                                          \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt) {                                             \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        i = 0;                                                          \
        memset(opts->name##s, 0x00, sizeof(opts->name##s));             \
        split_page = kstrdup(page, GFP_KERNEL);                         \
        while ((token = strsep(&split_page, ",")) != NULL) {            \
                ret = kstrtou32(token, 0, &num);                        \
                if (ret)                                                \
                        goto end;                                       \
                                                                        \
                opts->name##s[i++] = num;                               \
                ret = len;                                              \
        };                                                              \
                                                                        \
end:                                                                    \
        kfree(split_page);                                              \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_uac1_opts_, name)

#define UAC1_ATTRIBUTE_STRING(name)                                     \
static ssize_t f_uac1_opts_##name##_show(struct config_item *item,      \
                                         char *page)                    \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        result = sysfs_emit(page, "%s", opts->name);                    \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_uac1_opts_##name##_store(struct config_item *item,     \
                                          const char *page, size_t len) \
{                                                                       \
        struct f_uac1_opts *opts = to_f_uac1_opts(item);                \
        int ret = 0;                                                    \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt) {                                             \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        ret = scnprintf(opts->name, min(sizeof(opts->name), len),       \
                        "%s", page);                                    \
                                                                        \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_uac1_opts_, name)

UAC1_ATTRIBUTE(u32, c_chmask);
UAC1_RATE_ATTRIBUTE(c_srate);
UAC1_ATTRIBUTE(u32, c_ssize);
UAC1_ATTRIBUTE(u32, p_chmask);
UAC1_RATE_ATTRIBUTE(p_srate);
UAC1_ATTRIBUTE(u32, p_ssize);
UAC1_ATTRIBUTE(u32, req_number);

UAC1_ATTRIBUTE(bool, p_mute_present);
UAC1_ATTRIBUTE(bool, p_volume_present);
UAC1_ATTRIBUTE(s16, p_volume_min);
UAC1_ATTRIBUTE(s16, p_volume_max);
UAC1_ATTRIBUTE(s16, p_volume_res);

UAC1_ATTRIBUTE(bool, c_mute_present);
UAC1_ATTRIBUTE(bool, c_volume_present);
UAC1_ATTRIBUTE(s16, c_volume_min);
UAC1_ATTRIBUTE(s16, c_volume_max);
UAC1_ATTRIBUTE(s16, c_volume_res);

UAC1_ATTRIBUTE_STRING(function_name);

UAC1_ATTRIBUTE_STRING(p_it_name);
UAC1_ATTRIBUTE_STRING(p_it_ch_name);
UAC1_ATTRIBUTE_STRING(p_ot_name);
UAC1_ATTRIBUTE_STRING(p_fu_vol_name);

UAC1_ATTRIBUTE_STRING(c_it_name);
UAC1_ATTRIBUTE_STRING(c_it_ch_name);
UAC1_ATTRIBUTE_STRING(c_ot_name);
UAC1_ATTRIBUTE_STRING(c_fu_vol_name);

static struct configfs_attribute *f_uac1_attrs[] = {
        &f_uac1_opts_attr_c_chmask,
        &f_uac1_opts_attr_c_srate,
        &f_uac1_opts_attr_c_ssize,
        &f_uac1_opts_attr_p_chmask,
        &f_uac1_opts_attr_p_srate,
        &f_uac1_opts_attr_p_ssize,
        &f_uac1_opts_attr_req_number,

        &f_uac1_opts_attr_p_mute_present,
        &f_uac1_opts_attr_p_volume_present,
        &f_uac1_opts_attr_p_volume_min,
        &f_uac1_opts_attr_p_volume_max,
        &f_uac1_opts_attr_p_volume_res,

        &f_uac1_opts_attr_c_mute_present,
        &f_uac1_opts_attr_c_volume_present,
        &f_uac1_opts_attr_c_volume_min,
        &f_uac1_opts_attr_c_volume_max,
        &f_uac1_opts_attr_c_volume_res,

        &f_uac1_opts_attr_function_name,

        &f_uac1_opts_attr_p_it_name,
        &f_uac1_opts_attr_p_it_ch_name,
        &f_uac1_opts_attr_p_ot_name,
        &f_uac1_opts_attr_p_fu_vol_name,

        &f_uac1_opts_attr_c_it_name,
        &f_uac1_opts_attr_c_it_ch_name,
        &f_uac1_opts_attr_c_ot_name,
        &f_uac1_opts_attr_c_fu_vol_name,

        NULL,
};

static const struct config_item_type f_uac1_func_type = {
        .ct_item_ops    = &f_uac1_item_ops,
        .ct_attrs       = f_uac1_attrs,
        .ct_owner       = THIS_MODULE,
};

static void f_audio_free_inst(struct usb_function_instance *f)
{
        struct f_uac1_opts *opts;

        opts = container_of(f, struct f_uac1_opts, func_inst);
        kfree(opts);
}

static struct usb_function_instance *f_audio_alloc_inst(void)
{
        struct f_uac1_opts *opts;

        opts = kzalloc_obj(*opts);
        if (!opts)
                return ERR_PTR(-ENOMEM);

        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = f_audio_free_inst;

        config_group_init_type_name(&opts->func_inst.group, "",
                                    &f_uac1_func_type);

        opts->c_chmask = UAC1_DEF_CCHMASK;
        opts->c_srates[0] = UAC1_DEF_CSRATE;
        opts->c_ssize = UAC1_DEF_CSSIZE;
        opts->p_chmask = UAC1_DEF_PCHMASK;
        opts->p_srates[0] = UAC1_DEF_PSRATE;
        opts->p_ssize = UAC1_DEF_PSSIZE;

        opts->p_mute_present = UAC1_DEF_MUTE_PRESENT;
        opts->p_volume_present = UAC1_DEF_VOLUME_PRESENT;
        opts->p_volume_min = UAC1_DEF_MIN_DB;
        opts->p_volume_max = UAC1_DEF_MAX_DB;
        opts->p_volume_res = UAC1_DEF_RES_DB;

        opts->c_mute_present = UAC1_DEF_MUTE_PRESENT;
        opts->c_volume_present = UAC1_DEF_VOLUME_PRESENT;
        opts->c_volume_min = UAC1_DEF_MIN_DB;
        opts->c_volume_max = UAC1_DEF_MAX_DB;
        opts->c_volume_res = UAC1_DEF_RES_DB;

        opts->req_number = UAC1_DEF_REQ_NUM;

        scnprintf(opts->function_name, sizeof(opts->function_name), "AC Interface");

        scnprintf(opts->p_it_name, sizeof(opts->p_it_name), "Capture Input terminal");
        scnprintf(opts->p_it_ch_name, sizeof(opts->p_it_ch_name), "Capture Channels");
        scnprintf(opts->p_ot_name, sizeof(opts->p_ot_name), "Capture Output terminal");
        scnprintf(opts->p_fu_vol_name, sizeof(opts->p_fu_vol_name), "Capture Volume");

        scnprintf(opts->c_it_name, sizeof(opts->c_it_name), "Playback Input terminal");
        scnprintf(opts->c_it_ch_name, sizeof(opts->c_it_ch_name), "Playback Channels");
        scnprintf(opts->c_ot_name, sizeof(opts->c_ot_name), "Playback Output terminal");
        scnprintf(opts->c_fu_vol_name, sizeof(opts->c_fu_vol_name), "Playback Volume");

        return &opts->func_inst;
}

static void f_audio_free(struct usb_function *f)
{
        struct g_audio *audio;
        struct f_uac1_opts *opts;

        audio = func_to_g_audio(f);
        opts = container_of(f->fi, struct f_uac1_opts, func_inst);
        kfree(audio);
        mutex_lock(&opts->lock);
        --opts->refcnt;
        mutex_unlock(&opts->lock);
}

static void f_audio_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct g_audio *audio = func_to_g_audio(f);

        g_audio_cleanup(audio);
        usb_free_all_descriptors(f);

        kfree(out_feature_unit_desc);
        out_feature_unit_desc = NULL;
        kfree(in_feature_unit_desc);
        in_feature_unit_desc = NULL;

        kfree(ac_header_desc);
        ac_header_desc = NULL;

        audio->gadget = NULL;
}

static struct usb_function *f_audio_alloc(struct usb_function_instance *fi)
{
        struct f_uac1 *uac1;
        struct f_uac1_opts *opts;

        /* allocate and initialize one new instance */
        uac1 = kzalloc_obj(*uac1);
        if (!uac1)
                return ERR_PTR(-ENOMEM);

        opts = container_of(fi, struct f_uac1_opts, func_inst);
        mutex_lock(&opts->lock);
        ++opts->refcnt;
        mutex_unlock(&opts->lock);

        uac1->g_audio.func.name = "uac1_func";
        uac1->g_audio.func.bind = f_audio_bind;
        uac1->g_audio.func.unbind = f_audio_unbind;
        uac1->g_audio.func.set_alt = f_audio_set_alt;
        uac1->g_audio.func.get_alt = f_audio_get_alt;
        uac1->g_audio.func.setup = f_audio_setup;
        uac1->g_audio.func.disable = f_audio_disable;
        uac1->g_audio.func.suspend = f_audio_suspend;
        uac1->g_audio.func.free_func = f_audio_free;

        return &uac1->g_audio.func;
}

DECLARE_USB_FUNCTION_INIT(uac1, f_audio_alloc_inst, f_audio_alloc);
MODULE_DESCRIPTION("USB Audio Class 1.0 Function (using u_audio API)");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ruslan Bilovol");