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: NGerd Hoffmann <kraxel@redhat.com>

Makefile.objs

@@ -102,7 +102,7 @@ common-obj-y += scsi-disk.o cdrom.o
 common-obj-y += scsi-generic.o scsi-bus.o
 common-obj-y += hid.o
 common-obj-y += usb.o usb-hub.o usb-$(HOST_USB).o usb-hid.o usb-msd.o usb-wacom.o
-common-obj-y += usb-serial.o usb-net.o usb-bus.o usb-desc.o
+common-obj-y += usb-serial.o usb-net.o usb-bus.o usb-desc.o usb-audio.o
 common-obj-$(CONFIG_SSI) += ssi.o
 common-obj-$(CONFIG_SSI_SD) += ssi-sd.o
 common-obj-$(CONFIG_SD) += sd.o

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

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