usb: add audio device model

This brings a usb audio device to qemu.  Output only, fixed at
16bit stereo @ 480000 Hz.  Based on a patch from
H. Peter Anvin <hpa@linux.intel.com>

Usage: add '-device usb-audio' to your qemu command line.

Works sorta ok on a idle machine.  Known issues:

 * Is *very* sensitive to latencies.
 * Burns quite some CPU due to usb polling.

In short:  It brings the qemu usb emulation to its limits.  Enjoy!

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

3 files changed, 711 insertions, 3 deletions

diff --git a/hw/usb-audio.c b/hw/usb-audio.c
new file mode 100644
index 0000000..b22d578
--- /dev/null
+++ b/hw/usb-audio.c
@@ -0,0 +1,704 @@
+/*
+ * QEMU USB audio device
+ *
+ * written by:
+ *  H. Peter Anvin <hpa@linux.intel.com>
+ *  Gerd Hoffmann <kraxel@redhat.com>
+ *
+ * lousely based on usb net device code which is:
+ *
+ * Copyright (c) 2006 Thomas Sailer
+ * Copyright (c) 2008 Andrzej Zaborowski
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "usb.h"
+#include "usb-desc.h"
+#include "hw.h"
+#include "audiodev.h"
+#include "audio/audio.h"
+
+#define USBAUDIO_VENDOR_NUM     0x46f4 /* CRC16() of "QEMU" */
+#define USBAUDIO_PRODUCT_NUM    0x0002
+
+#define DEV_CONFIG_VALUE        1 /* The one and only */
+
+/* Descriptor subtypes for AC interfaces */
+#define DST_AC_HEADER           1
+#define DST_AC_INPUT_TERMINAL   2
+#define DST_AC_OUTPUT_TERMINAL  3
+#define DST_AC_FEATURE_UNIT     6
+/* Descriptor subtypes for AS interfaces */
+#define DST_AS_GENERAL          1
+#define DST_AS_FORMAT_TYPE      2
+/* Descriptor subtypes for endpoints */
+#define DST_EP_GENERAL          1
+
+enum usb_audio_strings {
+    STRING_NULL,
+    STRING_MANUFACTURER,
+    STRING_PRODUCT,
+    STRING_SERIALNUMBER,
+    STRING_CONFIG,
+    STRING_USBAUDIO_CONTROL,
+    STRING_INPUT_TERMINAL,
+    STRING_FEATURE_UNIT,
+    STRING_OUTPUT_TERMINAL,
+    STRING_NULL_STREAM,
+    STRING_REAL_STREAM,
+};
+
+static const USBDescStrings usb_audio_stringtable = {
+    [STRING_MANUFACTURER]       = "QEMU",
+    [STRING_PRODUCT]            = "QEMU USB Audio",
+    [STRING_SERIALNUMBER]       = "1",
+    [STRING_CONFIG]             = "Audio Configuration",
+    [STRING_USBAUDIO_CONTROL]   = "Audio Device",
+    [STRING_INPUT_TERMINAL]     = "Audio Output Pipe",
+    [STRING_FEATURE_UNIT]       = "Audio Output Volume Control",
+    [STRING_OUTPUT_TERMINAL]    = "Audio Output Terminal",
+    [STRING_NULL_STREAM]        = "Audio Output - Disabled",
+    [STRING_REAL_STREAM]        = "Audio Output - 48 kHz Stereo",
+};
+
+#define U16(x) ((x) & 0xff), (((x) >> 8) & 0xff)
+#define U24(x) U16(x), (((x) >> 16) & 0xff)
+#define U32(x) U24(x), (((x) >> 24) & 0xff)
+
+/*
+ * A Basic Audio Device uses these specific values
+ */
+#define USBAUDIO_PACKET_SIZE     192
+#define USBAUDIO_SAMPLE_RATE     48000
+#define USBAUDIO_PACKET_INTERVAL 1
+
+static const USBDescIface desc_iface[] = {
+    {
+        .bInterfaceNumber              = 0,
+        .bNumEndpoints                 = 0,
+        .bInterfaceClass               = USB_CLASS_AUDIO,
+        .bInterfaceSubClass            = USB_SUBCLASS_AUDIO_CONTROL,
+        .bInterfaceProtocol            = 0x04,
+        .iInterface                    = STRING_USBAUDIO_CONTROL,
+        .ndesc                         = 4,
+        .descs = (USBDescOther[]) {
+            {
+                /* Headphone Class-Specific AC Interface Header Descriptor */
+                .data = (uint8_t[]) {
+                    0x09,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AC_HEADER,              /*  u8  bDescriptorSubtype */
+                    U16(0x0100),                /* u16  bcdADC */
+                    U16(0x2b),                  /* u16  wTotalLength */
+                    0x01,                       /*  u8  bInCollection */
+                    0x01,                       /*  u8  baInterfaceNr */
+                }
+            },{
+                /* Generic Stereo Input Terminal ID1 Descriptor */
+                .data = (uint8_t[]) {
+                    0x0c,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AC_INPUT_TERMINAL,      /*  u8  bDescriptorSubtype */
+                    0x01,                       /*  u8  bTerminalID */
+                    U16(0x0101),                /* u16  wTerminalType */
+                    0x00,                       /*  u8  bAssocTerminal */
+                    0x02,                       /* u16  bNrChannels */
+                    U16(0x0003),                /* u16  wChannelConfig */
+                    0x00,                       /*  u8  iChannelNames */
+                    STRING_INPUT_TERMINAL,      /*  u8  iTerminal */
+                }
+            },{
+                /* Generic Stereo Feature Unit ID2 Descriptor */
+                .data = (uint8_t[]) {
+                    0x0d,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AC_FEATURE_UNIT,        /*  u8  bDescriptorSubtype */
+                    0x02,                       /*  u8  bUnitID */
+                    0x01,                       /*  u8  bSourceID */
+                    0x02,                       /*  u8  bControlSize */
+                    U16(0x0001),                /* u16  bmaControls(0) */
+                    U16(0x0002),                /* u16  bmaControls(1) */
+                    U16(0x0002),                /* u16  bmaControls(2) */
+                    STRING_FEATURE_UNIT,        /*  u8  iFeature */
+                }
+            },{
+                /* Headphone Ouptut Terminal ID3 Descriptor */
+                .data = (uint8_t[]) {
+                    0x09,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AC_OUTPUT_TERMINAL,     /*  u8  bDescriptorSubtype */
+                    0x03,                       /*  u8  bUnitID */
+                    U16(0x0301),                /* u16  wTerminalType (SPK) */
+                    0x00,                       /*  u8  bAssocTerminal */
+                    0x02,                       /*  u8  bSourceID */
+                    STRING_OUTPUT_TERMINAL,     /*  u8  iTerminal */
+                }
+            }
+        },
+    },{
+        .bInterfaceNumber              = 1,
+        .bAlternateSetting             = 0,
+        .bNumEndpoints                 = 0,
+        .bInterfaceClass               = USB_CLASS_AUDIO,
+        .bInterfaceSubClass            = USB_SUBCLASS_AUDIO_STREAMING,
+        .iInterface                    = STRING_NULL_STREAM,
+    },{
+        .bInterfaceNumber              = 1,
+        .bAlternateSetting             = 1,
+        .bNumEndpoints                 = 1,
+        .bInterfaceClass               = USB_CLASS_AUDIO,
+        .bInterfaceSubClass            = USB_SUBCLASS_AUDIO_STREAMING,
+        .iInterface                    = STRING_REAL_STREAM,
+        .ndesc                         = 2,
+        .descs = (USBDescOther[]) {
+            {
+                /* Headphone Class-specific AS General Interface Descriptor */
+                .data = (uint8_t[]) {
+                    0x07,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AS_GENERAL,             /*  u8  bDescriptorSubtype */
+                    0x01,                       /*  u8  bTerminalLink */
+                    0x00,                       /*  u8  bDelay */
+                    0x01, 0x00,                 /* u16  wFormatTag */
+                }
+            },{
+                /* Headphone Type I Format Type Descriptor */
+                .data = (uint8_t[]) {
+                    0x0b,                       /*  u8  bLength */
+                    USB_DT_CS_INTERFACE,        /*  u8  bDescriptorType */
+                    DST_AS_FORMAT_TYPE,         /*  u8  bDescriptorSubtype */
+                    0x01,                       /*  u8  bFormatType */
+                    0x02,                       /*  u8  bNrChannels */
+                    0x02,                       /*  u8  bSubFrameSize */
+                    0x10,                       /*  u8  bBitResolution */
+                    0x01,                       /*  u8  bSamFreqType */
+                    U24(USBAUDIO_SAMPLE_RATE),  /* u24  tSamFreq */
+                }
+            }
+        },
+        .eps = (USBDescEndpoint[]) {
+            {
+                .bEndpointAddress      = USB_DIR_OUT | 0x01,
+                .bmAttributes          = 0x0d,
+                .wMaxPacketSize        = USBAUDIO_PACKET_SIZE,
+                .bInterval             = 1,
+                .is_audio              = 1,
+                /* Stereo Headphone Class-specific
+                   AS Audio Data Endpoint Descriptor */
+                .extra = (uint8_t[]) {
+                    0x07,                       /*  u8  bLength */
+                    USB_DT_CS_ENDPOINT,         /*  u8  bDescriptorType */
+                    DST_EP_GENERAL,             /*  u8  bDescriptorSubtype */
+                    0x00,                       /*  u8  bmAttributes */
+                    0x00,                       /*  u8  bLockDelayUnits */
+                    U16(0x0000),                /* u16  wLockDelay */
+                },
+            },
+        }
+    }
+};
+
+static const USBDescDevice desc_device = {
+    .bcdUSB                        = 0x0200,
+    .bMaxPacketSize0               = 64,
+    .bNumConfigurations            = 1,
+    .confs = (USBDescConfig[]) {
+        {
+            .bNumInterfaces        = 2,
+            .bConfigurationValue   = DEV_CONFIG_VALUE,
+            .iConfiguration        = STRING_CONFIG,
+            .bmAttributes          = 0xc0,
+            .bMaxPower             = 0x32,
+            .nif = ARRAY_SIZE(desc_iface),
+            .ifs = desc_iface,
+        },
+    },
+};
+
+static const USBDesc desc_audio = {
+    .id = {
+        .idVendor          = USBAUDIO_VENDOR_NUM,
+        .idProduct         = USBAUDIO_PRODUCT_NUM,
+        .bcdDevice         = 0,
+        .iManufacturer     = STRING_MANUFACTURER,
+        .iProduct          = STRING_PRODUCT,
+        .iSerialNumber     = STRING_SERIALNUMBER,
+    },
+    .full = &desc_device,
+    .str  = usb_audio_stringtable,
+};
+
+/*
+ * A USB audio device supports an arbitrary number of alternate
+ * interface settings for each interface.  Each corresponds to a block
+ * diagram of parameterized blocks.  This can thus refer to things like
+ * number of channels, data rates, or in fact completely different
+ * block diagrams.  Alternative setting 0 is always the null block diagram,
+ * which is used by a disabled device.
+ */
+enum usb_audio_altset {
+    ALTSET_OFF  = 0x00,         /* No endpoint */
+    ALTSET_ON   = 0x01,         /* Single endpoint */
+};
+
+/*
+ * Class-specific control requests
+ */
+#define CR_SET_CUR      0x01
+#define CR_GET_CUR      0x81
+#define CR_SET_MIN      0x02
+#define CR_GET_MIN      0x82
+#define CR_SET_MAX      0x03
+#define CR_GET_MAX      0x83
+#define CR_SET_RES      0x04
+#define CR_GET_RES      0x84
+#define CR_SET_MEM      0x05
+#define CR_GET_MEM      0x85
+#define CR_GET_STAT     0xff
+
+/*
+ * Feature Unit Control Selectors
+ */
+#define MUTE_CONTROL                    0x01
+#define VOLUME_CONTROL                  0x02
+#define BASS_CONTROL                    0x03
+#define MID_CONTROL                     0x04
+#define TREBLE_CONTROL                  0x05
+#define GRAPHIC_EQUALIZER_CONTROL       0x06
+#define AUTOMATIC_GAIN_CONTROL          0x07
+#define DELAY_CONTROL                   0x08
+#define BASS_BOOST_CONTROL              0x09
+#define LOUDNESS_CONTROL                0x0a
+
+/*
+ * buffering
+ */
+
+struct streambuf {
+    uint8_t *data;
+    uint32_t size;
+    uint32_t prod;
+    uint32_t cons;
+};
+
+static void streambuf_init(struct streambuf *buf, uint32_t size)
+{
+    g_free(buf->data);
+    buf->size = size - (size % USBAUDIO_PACKET_SIZE);
+    buf->data = g_malloc(buf->size);
+    buf->prod = 0;
+    buf->cons = 0;
+}
+
+static void streambuf_fini(struct streambuf *buf)
+{
+    g_free(buf->data);
+    buf->data = NULL;
+}
+
+static int streambuf_put(struct streambuf *buf, USBPacket *p)
+{
+    uint32_t free = buf->size - (buf->prod - buf->cons);
+
+    if (!free) {
+        return 0;
+    }
+    assert(free >= USBAUDIO_PACKET_SIZE);
+    usb_packet_copy(p, buf->data + (buf->prod % buf->size),
+                    USBAUDIO_PACKET_SIZE);
+    buf->prod += USBAUDIO_PACKET_SIZE;
+    return USBAUDIO_PACKET_SIZE;
+}
+
+static uint8_t *streambuf_get(struct streambuf *buf)
+{
+    uint32_t used = buf->prod - buf->cons;
+    uint8_t *data;
+
+    if (!used) {
+        return NULL;
+    }
+    assert(used >= USBAUDIO_PACKET_SIZE);
+    data = buf->data + (buf->cons % buf->size);
+    buf->cons += USBAUDIO_PACKET_SIZE;
+    return data;
+}
+
+typedef struct USBAudioState {
+    /* qemu interfaces */
+    USBDevice dev;
+    QEMUSoundCard card;
+
+    /* state */
+    struct {
+        enum usb_audio_altset altset;
+        struct audsettings as;
+        SWVoiceOut *voice;
+        bool mute;
+        uint8_t vol[2];
+        struct streambuf buf;
+    } out;
+
+    /* properties */
+    uint32_t debug;
+    uint32_t buffer;
+} USBAudioState;
+
+static void output_callback(void *opaque, int avail)
+{
+    USBAudioState *s = opaque;
+    uint8_t *data;
+
+    for (;;) {
+        if (avail < USBAUDIO_PACKET_SIZE) {
+            return;
+        }
+        data = streambuf_get(&s->out.buf);
+        if (NULL == data) {
+            return;
+        }
+        AUD_write(s->out.voice, data, USBAUDIO_PACKET_SIZE);
+        avail -= USBAUDIO_PACKET_SIZE;
+    }
+}
+
+static int usb_audio_set_output_altset(USBAudioState *s, int altset)
+{
+    switch (altset) {
+    case ALTSET_OFF:
+        streambuf_init(&s->out.buf, s->buffer);
+        AUD_set_active_out(s->out.voice, false);
+        break;
+    case ALTSET_ON:
+        AUD_set_active_out(s->out.voice, true);
+        break;
+    default:
+        return -1;
+    }
+
+    if (s->debug) {
+        fprintf(stderr, "usb-audio: set interface %d\n", altset);
+    }
+    s->out.altset = altset;
+    return 0;
+}
+
+/*
+ * Note: we arbitrarily map the volume control range onto -inf..+8 dB
+ */
+#define ATTRIB_ID(cs, attrib, idif)     \
+    (((cs) << 24) | ((attrib) << 16) | (idif))
+
+static int usb_audio_get_control(USBAudioState *s, uint8_t attrib,
+                                 uint16_t cscn, uint16_t idif,
+                                 int length, uint8_t *data)
+{
+    uint8_t cs = cscn >> 8;
+    uint8_t cn = cscn - 1;      /* -1 for the non-present master control */
+    uint32_t aid = ATTRIB_ID(cs, attrib, idif);
+    int ret = USB_RET_STALL;
+
+    switch (aid) {
+    case ATTRIB_ID(MUTE_CONTROL, CR_GET_CUR, 0x0200):
+        data[0] = s->out.mute;
+        ret = 1;
+        break;
+    case ATTRIB_ID(VOLUME_CONTROL, CR_GET_CUR, 0x0200):
+        if (cn < 2) {
+            uint16_t vol = (s->out.vol[cn] * 0x8800 + 127) / 255 + 0x8000;
+            data[0] = vol;
+            data[1] = vol >> 8;
+            ret = 2;
+        }
+        break;
+    case ATTRIB_ID(VOLUME_CONTROL, CR_GET_MIN, 0x0200):
+        if (cn < 2) {
+            data[0] = 0x01;
+            data[1] = 0x80;
+            ret = 2;
+        }
+        break;
+    case ATTRIB_ID(VOLUME_CONTROL, CR_GET_MAX, 0x0200):
+        if (cn < 2) {
+            data[0] = 0x00;
+            data[1] = 0x08;
+            ret = 2;
+        }
+        break;
+    case ATTRIB_ID(VOLUME_CONTROL, CR_GET_RES, 0x0200):
+        if (cn < 2) {
+            data[0] = 0x88;
+            data[1] = 0x00;
+            ret = 2;
+        }
+        break;
+    }
+
+    return ret;
+}
+static int usb_audio_set_control(USBAudioState *s, uint8_t attrib,
+                                 uint16_t cscn, uint16_t idif,
+                                 int length, uint8_t *data)
+{
+    uint8_t cs = cscn >> 8;
+    uint8_t cn = cscn - 1;      /* -1 for the non-present master control */
+    uint32_t aid = ATTRIB_ID(cs, attrib, idif);
+    int ret = USB_RET_STALL;
+    bool set_vol = false;
+
+    switch (aid) {
+    case ATTRIB_ID(MUTE_CONTROL, CR_SET_CUR, 0x0200):
+        s->out.mute = data[0] & 1;
+        set_vol = true;
+        ret = 0;
+        break;
+    case ATTRIB_ID(VOLUME_CONTROL, CR_SET_CUR, 0x0200):
+        if (cn < 2) {
+            uint16_t vol = data[0] + (data[1] << 8);
+
+            if (s->debug) {
+                fprintf(stderr, "usb-audio: vol %04x\n", (uint16_t)vol);
+            }
+
+            vol -= 0x8000;
+            vol = (vol * 255 + 0x4400) / 0x8800;
+            if (vol > 255) {
+                vol = 255;
+            }
+
+            s->out.vol[cn] = vol;
+            set_vol = true;
+            ret = 0;
+        }
+        break;
+    }
+
+    if (set_vol) {
+        if (s->debug) {
+            fprintf(stderr, "usb-audio: mute %d, lvol %3d, rvol %3d\n",
+                    s->out.mute, s->out.vol[0], s->out.vol[1]);
+        }
+        AUD_set_volume_out(s->out.voice, s->out.mute,
+                           s->out.vol[0], s->out.vol[1]);
+    }
+
+    return ret;
+}
+
+static int usb_audio_handle_control(USBDevice *dev, USBPacket *p,
+                                    int request, int value, int index,
+                                    int length, uint8_t *data)
+{
+    USBAudioState *s = DO_UPCAST(USBAudioState, dev, dev);
+    int ret = 0;
+
+    if (s->debug) {
+        fprintf(stderr, "usb-audio: control transaction: "
+                "request 0x%04x value 0x%04x index 0x%04x length 0x%04x\n",
+                request, value, index, length);
+    }
+
+    ret = usb_desc_handle_control(dev, p, request, value, index, length, data);
+    if (ret >= 0) {
+        return ret;
+    }
+
+    switch (request) {
+    case ClassInterfaceRequest | CR_GET_CUR:
+    case ClassInterfaceRequest | CR_GET_MIN:
+    case ClassInterfaceRequest | CR_GET_MAX:
+    case ClassInterfaceRequest | CR_GET_RES:
+        ret = usb_audio_get_control(s, request & 0xff, value, index,
+                                    length, data);
+        if (ret < 0) {
+            if (s->debug) {
+                fprintf(stderr, "usb-audio: fail: get control\n");
+            }
+            goto fail;
+        }
+        break;
+
+    case ClassInterfaceOutRequest | CR_SET_CUR:
+    case ClassInterfaceOutRequest | CR_SET_MIN:
+    case ClassInterfaceOutRequest | CR_SET_MAX:
+    case ClassInterfaceOutRequest | CR_SET_RES:
+        ret = usb_audio_set_control(s, request & 0xff, value, index,
+                                    length, data);
+        if (ret < 0) {
+            if (s->debug) {
+                fprintf(stderr, "usb-audio: fail: set control\n");
+            }
+            goto fail;
+        }
+        break;
+
+    default:
+fail:
+        if (s->debug) {
+            fprintf(stderr, "usb-audio: failed control transaction: "
+                    "request 0x%04x value 0x%04x index 0x%04x length 0x%04x\n",
+                    request, value, index, length);
+        }
+        ret = USB_RET_STALL;
+        break;
+    }
+    return ret;
+}
+
+static void usb_audio_set_interface(USBDevice *dev, int iface,
+                                    int old, int value)
+{
+    USBAudioState *s = DO_UPCAST(USBAudioState, dev, dev);
+
+    if (iface == 1) {
+        usb_audio_set_output_altset(s, value);
+    }
+}
+
+static void usb_audio_handle_reset(USBDevice *dev)
+{
+    USBAudioState *s = DO_UPCAST(USBAudioState, dev, dev);
+
+    if (s->debug) {
+        fprintf(stderr, "usb-audio: reset\n");
+    }
+    usb_audio_set_output_altset(s, ALTSET_OFF);
+}
+
+static int usb_audio_handle_dataout(USBAudioState *s, USBPacket *p)
+{
+    int rc;
+
+    if (s->out.altset == ALTSET_OFF) {
+        return USB_RET_STALL;
+    }
+
+    rc = streambuf_put(&s->out.buf, p);
+    if (rc < p->iov.size && s->debug > 1) {
+        fprintf(stderr, "usb-audio: output overrun (%zd bytes)\n",
+                p->iov.size - rc);
+    }
+
+    return 0;
+}
+
+static int usb_audio_handle_data(USBDevice *dev, USBPacket *p)
+{
+    USBAudioState *s = (USBAudioState *) dev;
+    int ret = 0;
+
+    switch (p->pid) {
+    case USB_TOKEN_OUT:
+        switch (p->devep) {
+        case 1:
+            ret = usb_audio_handle_dataout(s, p);
+            break;
+        default:
+            goto fail;
+        }
+        break;
+
+    default:
+fail:
+        ret = USB_RET_STALL;
+        break;
+    }
+    if (ret == USB_RET_STALL && s->debug) {
+        fprintf(stderr, "usb-audio: failed data transaction: "
+                        "pid 0x%x ep 0x%x len 0x%zx\n",
+                        p->pid, p->devep, p->iov.size);
+    }
+    return ret;
+}
+
+static void usb_audio_handle_destroy(USBDevice *dev)
+{
+    USBAudioState *s = DO_UPCAST(USBAudioState, dev, dev);
+
+    if (s->debug) {
+        fprintf(stderr, "usb-audio: destroy\n");
+    }
+
+    usb_audio_set_output_altset(s, ALTSET_OFF);
+    AUD_close_out(&s->card, s->out.voice);
+    AUD_remove_card(&s->card);
+
+    streambuf_fini(&s->out.buf);
+}
+
+static int usb_audio_initfn(USBDevice *dev)
+{
+    USBAudioState *s = DO_UPCAST(USBAudioState, dev, dev);
+
+    usb_desc_init(dev);
+    s->dev.opaque = s;
+    AUD_register_card("usb-audio", &s->card);
+
+    s->out.altset        = ALTSET_OFF;
+    s->out.mute          = false;
+    s->out.vol[0]        = 240; /* 0 dB */
+    s->out.vol[1]        = 240; /* 0 dB */
+    s->out.as.freq       = USBAUDIO_SAMPLE_RATE;
+    s->out.as.nchannels  = 2;
+    s->out.as.fmt        = AUD_FMT_S16;
+    s->out.as.endianness = 0;
+    streambuf_init(&s->out.buf, s->buffer);
+
+    s->out.voice = AUD_open_out(&s->card, s->out.voice, "usb-audio",
+                                s, output_callback, &s->out.as);
+    AUD_set_volume_out(s->out.voice, s->out.mute, s->out.vol[0], s->out.vol[1]);
+    AUD_set_active_out(s->out.voice, 0);
+    return 0;
+}
+
+static const VMStateDescription vmstate_usb_audio = {
+    .name = "usb-audio",
+    .unmigratable = 1,
+};
+
+static struct USBDeviceInfo usb_audio_info = {
+    .product_desc   = "QEMU USB Audio Interface",
+    .usbdevice_name = "audio",
+    .qdev.name      = "usb-audio",
+    .qdev.size      = sizeof(USBAudioState),
+    .qdev.vmsd      = &vmstate_usb_audio,
+    .usb_desc       = &desc_audio,
+    .init           = usb_audio_initfn,
+    .handle_packet  = usb_generic_handle_packet,
+    .handle_reset   = usb_audio_handle_reset,
+    .handle_control = usb_audio_handle_control,
+    .handle_data    = usb_audio_handle_data,
+    .handle_destroy = usb_audio_handle_destroy,
+    .set_interface  = usb_audio_set_interface,
+    .qdev.props = (Property[]) {
+        DEFINE_PROP_UINT32("debug", USBAudioState, debug, 0),
+        DEFINE_PROP_UINT32("buffer", USBAudioState, buffer,
+                           8 * USBAUDIO_PACKET_SIZE),
+        DEFINE_PROP_END_OF_LIST(),
+    }
+};
+
+static void usb_audio_register_devices(void)
+{
+    usb_qdev_register(&usb_audio_info);
+}
+
+device_init(usb_audio_register_devices)
diff --git a/hw/usb-net.c b/hw/usb-net.c
index 5622bed..2f527a8 100644
--- a/hw/usb-net.c
+++ b/hw/usb-net.c
@@ -71,9 +71,6 @@ enum usbstring_idx {
 #define USB_CDC_UNION_TYPE		0x06	/* union_desc */
 #define USB_CDC_ETHERNET_TYPE		0x0f	/* ether_desc */
 
-#define USB_DT_CS_INTERFACE		0x24
-#define USB_DT_CS_ENDPOINT		0x25
-
 #define USB_CDC_SEND_ENCAPSULATED_COMMAND	0x00
 #define USB_CDC_GET_ENCAPSULATED_RESPONSE	0x01
 #define USB_CDC_REQ_SET_LINE_CODING		0x20
diff --git a/hw/usb.h b/hw/usb.h
index 1496f76..b2c9479 100644
--- a/hw/usb.h
+++ b/hw/usb.h
@@ -79,6 +79,11 @@
 #define USB_CLASS_APP_SPEC		0xfe
 #define USB_CLASS_VENDOR_SPEC		0xff
 
+#define USB_SUBCLASS_UNDEFINED          0
+#define USB_SUBCLASS_AUDIO_CONTROL      1
+#define USB_SUBCLASS_AUDIO_STREAMING    2
+#define USB_SUBCLASS_AUDIO_MIDISTREAMING 3
+
 #define USB_DIR_OUT			0
 #define USB_DIR_IN			0x80
 
@@ -132,6 +137,8 @@
 #define USB_DT_OTHER_SPEED_CONFIG       0x07
 #define USB_DT_DEBUG                    0x0A
 #define USB_DT_INTERFACE_ASSOC          0x0B
+#define USB_DT_CS_INTERFACE             0x24
+#define USB_DT_CS_ENDPOINT              0x25
 
 #define USB_ENDPOINT_XFER_CONTROL	0
 #define USB_ENDPOINT_XFER_ISOC		1