USB gadget: video class function driver

This USB video class function driver implements a video capture device from the
host's point of view. It creates a V4L2 output device on the gadget's side to
transfer data from a userspace application over USB.

The UVC-specific descriptors are passed by the gadget driver to the UVC
function driver, making them completely configurable without any modification
to the function's driver code.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/f_uvc.h

+/*
+ *	f_uvc.h  --  USB Video Class Gadget driver
+ *
+ *	Copyright (C) 2009-2010
+ *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#ifndef _F_UVC_H_
+#define _F_UVC_H_
+
+#include <linux/usb/composite.h>
+
+#define USB_CLASS_VIDEO_CONTROL		1
+#define USB_CLASS_VIDEO_STREAMING	2
+
+struct uvc_descriptor_header {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+} __attribute__ ((packed));
+
+struct uvc_header_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u16 bcdUVC;
+	__u16 wTotalLength;
+	__u32 dwClockFrequency;
+	__u8  bInCollection;
+	__u8  baInterfaceNr[];
+} __attribute__((__packed__));
+
+#define UVC_HEADER_DESCRIPTOR(n)	uvc_header_descriptor_##n
+
+#define DECLARE_UVC_HEADER_DESCRIPTOR(n) 			\
+struct UVC_HEADER_DESCRIPTOR(n) {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u16 bcdUVC;						\
+	__u16 wTotalLength;					\
+	__u32 dwClockFrequency;					\
+	__u8  bInCollection;					\
+	__u8  baInterfaceNr[n];					\
+} __attribute__ ((packed))
+
+struct uvc_input_terminal_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bTerminalID;
+	__u16 wTerminalType;
+	__u8  bAssocTerminal;
+	__u8  iTerminal;
+} __attribute__((__packed__));
+
+struct uvc_output_terminal_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bTerminalID;
+	__u16 wTerminalType;
+	__u8  bAssocTerminal;
+	__u8  bSourceID;
+	__u8  iTerminal;
+} __attribute__((__packed__));
+
+struct uvc_camera_terminal_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bTerminalID;
+	__u16 wTerminalType;
+	__u8  bAssocTerminal;
+	__u8  iTerminal;
+	__u16 wObjectiveFocalLengthMin;
+	__u16 wObjectiveFocalLengthMax;
+	__u16 wOcularFocalLength;
+	__u8  bControlSize;
+	__u8  bmControls[3];
+} __attribute__((__packed__));
+
+struct uvc_selector_unit_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bUnitID;
+	__u8  bNrInPins;
+	__u8  baSourceID[0];
+	__u8  iSelector;
+} __attribute__((__packed__));
+
+#define UVC_SELECTOR_UNIT_DESCRIPTOR(n)	\
+	uvc_selector_unit_descriptor_##n
+
+#define DECLARE_UVC_SELECTOR_UNIT_DESCRIPTOR(n) 		\
+struct UVC_SELECTOR_UNIT_DESCRIPTOR(n) {			\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bUnitID;						\
+	__u8  bNrInPins;					\
+	__u8  baSourceID[n];					\
+	__u8  iSelector;					\
+} __attribute__ ((packed))
+
+struct uvc_processing_unit_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bUnitID;
+	__u8  bSourceID;
+	__u16 wMaxMultiplier;
+	__u8  bControlSize;
+	__u8  bmControls[2];
+	__u8  iProcessing;
+} __attribute__((__packed__));
+
+struct uvc_extension_unit_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bUnitID;
+	__u8  guidExtensionCode[16];
+	__u8  bNumControls;
+	__u8  bNrInPins;
+	__u8  baSourceID[0];
+	__u8  bControlSize;
+	__u8  bmControls[0];
+	__u8  iExtension;
+} __attribute__((__packed__));
+
+#define UVC_EXTENSION_UNIT_DESCRIPTOR(p, n) \
+	uvc_extension_unit_descriptor_##p_##n
+
+#define DECLARE_UVC_EXTENSION_UNIT_DESCRIPTOR(p, n) 		\
+struct UVC_EXTENSION_UNIT_DESCRIPTOR(p, n) {			\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bUnitID;						\
+	__u8  guidExtensionCode[16];				\
+	__u8  bNumControls;					\
+	__u8  bNrInPins;					\
+	__u8  baSourceID[p];					\
+	__u8  bControlSize;					\
+	__u8  bmControls[n];					\
+	__u8  iExtension;					\
+} __attribute__ ((packed))
+
+struct uvc_control_endpoint_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u16 wMaxTransferSize;
+} __attribute__((__packed__));
+
+#define UVC_DT_HEADER				1
+#define UVC_DT_INPUT_TERMINAL			2
+#define UVC_DT_OUTPUT_TERMINAL			3
+#define UVC_DT_SELECTOR_UNIT			4
+#define UVC_DT_PROCESSING_UNIT			5
+#define UVC_DT_EXTENSION_UNIT			6
+
+#define UVC_DT_HEADER_SIZE(n)			(12+(n))
+#define UVC_DT_INPUT_TERMINAL_SIZE		8
+#define UVC_DT_OUTPUT_TERMINAL_SIZE		9
+#define UVC_DT_CAMERA_TERMINAL_SIZE(n)		(15+(n))
+#define UVC_DT_SELECTOR_UNIT_SIZE(n)		(6+(n))
+#define UVC_DT_PROCESSING_UNIT_SIZE(n)		(9+(n))
+#define UVC_DT_EXTENSION_UNIT_SIZE(p,n)		(24+(p)+(n))
+#define UVC_DT_CONTROL_ENDPOINT_SIZE		5
+
+struct uvc_input_header_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bNumFormats;
+	__u16 wTotalLength;
+	__u8  bEndpointAddress;
+	__u8  bmInfo;
+	__u8  bTerminalLink;
+	__u8  bStillCaptureMethod;
+	__u8  bTriggerSupport;
+	__u8  bTriggerUsage;
+	__u8  bControlSize;
+	__u8  bmaControls[];
+} __attribute__((__packed__));
+
+#define UVC_INPUT_HEADER_DESCRIPTOR(n, p) \
+	uvc_input_header_descriptor_##n_##p
+
+#define DECLARE_UVC_INPUT_HEADER_DESCRIPTOR(n, p)		\
+struct UVC_INPUT_HEADER_DESCRIPTOR(n, p) {			\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bNumFormats;					\
+	__u16 wTotalLength;					\
+	__u8  bEndpointAddress;					\
+	__u8  bmInfo;						\
+	__u8  bTerminalLink;					\
+	__u8  bStillCaptureMethod;				\
+	__u8  bTriggerSupport;					\
+	__u8  bTriggerUsage;					\
+	__u8  bControlSize;					\
+	__u8  bmaControls[p][n];				\
+} __attribute__ ((packed))
+
+struct uvc_output_header_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bNumFormats;
+	__u16 wTotalLength;
+	__u8  bEndpointAddress;
+	__u8  bTerminalLink;
+	__u8  bControlSize;
+	__u8  bmaControls[];
+} __attribute__((__packed__));
+
+#define UVC_OUTPUT_HEADER_DESCRIPTOR(n, p) \
+	uvc_output_header_descriptor_##n_##p
+
+#define DECLARE_UVC_OUTPUT_HEADER_DESCRIPTOR(n, p)		\
+struct UVC_OUTPUT_HEADER_DESCRIPTOR(n, p) {			\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bNumFormats;					\
+	__u16 wTotalLength;					\
+	__u8  bEndpointAddress;					\
+	__u8  bTerminalLink;					\
+	__u8  bControlSize;					\
+	__u8  bmaControls[p][n];				\
+} __attribute__ ((packed))
+
+struct uvc_format_uncompressed {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bFormatIndex;
+	__u8  bNumFrameDescriptors;
+	__u8  guidFormat[16];
+	__u8  bBitsPerPixel;
+	__u8  bDefaultFrameIndex;
+	__u8  bAspectRatioX;
+	__u8  bAspectRatioY;
+	__u8  bmInterfaceFlags;
+	__u8  bCopyProtect;
+} __attribute__((__packed__));
+
+struct uvc_frame_uncompressed {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bFrameIndex;
+	__u8  bmCapabilities;
+	__u16 wWidth;
+	__u16 wHeight;
+	__u32 dwMinBitRate;
+	__u32 dwMaxBitRate;
+	__u32 dwMaxVideoFrameBufferSize;
+	__u32 dwDefaultFrameInterval;
+	__u8  bFrameIntervalType;
+	__u32 dwFrameInterval[];
+} __attribute__((__packed__));
+
+#define UVC_FRAME_UNCOMPRESSED(n) \
+	uvc_frame_uncompressed_##n
+
+#define DECLARE_UVC_FRAME_UNCOMPRESSED(n) 			\
+struct UVC_FRAME_UNCOMPRESSED(n) {				\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bFrameIndex;					\
+	__u8  bmCapabilities;					\
+	__u16 wWidth;						\
+	__u16 wHeight;						\
+	__u32 dwMinBitRate;					\
+	__u32 dwMaxBitRate;					\
+	__u32 dwMaxVideoFrameBufferSize;			\
+	__u32 dwDefaultFrameInterval;				\
+	__u8  bFrameIntervalType;				\
+	__u32 dwFrameInterval[n];				\
+} __attribute__ ((packed))
+
+struct uvc_format_mjpeg {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bFormatIndex;
+	__u8  bNumFrameDescriptors;
+	__u8  bmFlags;
+	__u8  bDefaultFrameIndex;
+	__u8  bAspectRatioX;
+	__u8  bAspectRatioY;
+	__u8  bmInterfaceFlags;
+	__u8  bCopyProtect;
+} __attribute__((__packed__));
+
+struct uvc_frame_mjpeg {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bFrameIndex;
+	__u8  bmCapabilities;
+	__u16 wWidth;
+	__u16 wHeight;
+	__u32 dwMinBitRate;
+	__u32 dwMaxBitRate;
+	__u32 dwMaxVideoFrameBufferSize;
+	__u32 dwDefaultFrameInterval;
+	__u8  bFrameIntervalType;
+	__u32 dwFrameInterval[];
+} __attribute__((__packed__));
+
+#define UVC_FRAME_MJPEG(n) \
+	uvc_frame_mjpeg_##n
+
+#define DECLARE_UVC_FRAME_MJPEG(n) 				\
+struct UVC_FRAME_MJPEG(n) {					\
+	__u8  bLength;						\
+	__u8  bDescriptorType;					\
+	__u8  bDescriptorSubType;				\
+	__u8  bFrameIndex;					\
+	__u8  bmCapabilities;					\
+	__u16 wWidth;						\
+	__u16 wHeight;						\
+	__u32 dwMinBitRate;					\
+	__u32 dwMaxBitRate;					\
+	__u32 dwMaxVideoFrameBufferSize;			\
+	__u32 dwDefaultFrameInterval;				\
+	__u8  bFrameIntervalType;				\
+	__u32 dwFrameInterval[n];				\
+} __attribute__ ((packed))
+
+struct uvc_color_matching_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bDescriptorSubType;
+	__u8  bColorPrimaries;
+	__u8  bTransferCharacteristics;
+	__u8  bMatrixCoefficients;
+} __attribute__((__packed__));
+
+#define UVC_DT_INPUT_HEADER			1
+#define UVC_DT_OUTPUT_HEADER			2
+#define UVC_DT_FORMAT_UNCOMPRESSED		4
+#define UVC_DT_FRAME_UNCOMPRESSED		5
+#define UVC_DT_FORMAT_MJPEG			6
+#define UVC_DT_FRAME_MJPEG			7
+#define UVC_DT_COLOR_MATCHING			13
+
+#define UVC_DT_INPUT_HEADER_SIZE(n, p)		(13+(n*p))
+#define UVC_DT_OUTPUT_HEADER_SIZE(n, p)		(9+(n*p))
+#define UVC_DT_FORMAT_UNCOMPRESSED_SIZE		27
+#define UVC_DT_FRAME_UNCOMPRESSED_SIZE(n)	(26+4*(n))
+#define UVC_DT_FORMAT_MJPEG_SIZE		11
+#define UVC_DT_FRAME_MJPEG_SIZE(n)		(26+4*(n))
+#define UVC_DT_COLOR_MATCHING_SIZE		6
+
+extern int uvc_bind_config(struct usb_configuration *c,
+			   const struct uvc_descriptor_header * const *control,
+			   const struct uvc_descriptor_header * const *fs_streaming,
+			   const struct uvc_descriptor_header * const *hs_streaming);
+
+#endif /* _F_UVC_H_ */
+

drivers/usb/gadget/uvc.h

+/*
+ *	uvc_gadget.h  --  USB Video Class Gadget driver
+ *
+ *	Copyright (C) 2009-2010
+ *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#ifndef _UVC_GADGET_H_
+#define _UVC_GADGET_H_
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+#include <linux/usb/ch9.h>
+
+#define UVC_EVENT_FIRST			(V4L2_EVENT_PRIVATE_START + 0)
+#define UVC_EVENT_CONNECT		(V4L2_EVENT_PRIVATE_START + 0)
+#define UVC_EVENT_DISCONNECT		(V4L2_EVENT_PRIVATE_START + 1)
+#define UVC_EVENT_STREAMON		(V4L2_EVENT_PRIVATE_START + 2)
+#define UVC_EVENT_STREAMOFF		(V4L2_EVENT_PRIVATE_START + 3)
+#define UVC_EVENT_SETUP			(V4L2_EVENT_PRIVATE_START + 4)
+#define UVC_EVENT_DATA			(V4L2_EVENT_PRIVATE_START + 5)
+#define UVC_EVENT_LAST			(V4L2_EVENT_PRIVATE_START + 5)
+
+struct uvc_request_data
+{
+	unsigned int length;
+	__u8 data[60];
+};
+
+struct uvc_event
+{
+	union {
+		enum usb_device_speed speed;
+		struct usb_ctrlrequest req;
+		struct uvc_request_data data;
+	};
+};
+
+#define UVCIOC_SEND_RESPONSE		_IOW('U', 1, struct uvc_request_data)
+
+#define UVC_INTF_CONTROL		0
+#define UVC_INTF_STREAMING		1
+
+/* ------------------------------------------------------------------------
+ * UVC constants & structures
+ */
+
+/* Values for bmHeaderInfo (Video and Still Image Payload Headers, 2.4.3.3) */
+#define UVC_STREAM_EOH				(1 << 7)
+#define UVC_STREAM_ERR				(1 << 6)
+#define UVC_STREAM_STI				(1 << 5)
+#define UVC_STREAM_RES				(1 << 4)
+#define UVC_STREAM_SCR				(1 << 3)
+#define UVC_STREAM_PTS				(1 << 2)
+#define UVC_STREAM_EOF				(1 << 1)
+#define UVC_STREAM_FID				(1 << 0)
+
+struct uvc_streaming_control {
+	__u16 bmHint;
+	__u8  bFormatIndex;
+	__u8  bFrameIndex;
+	__u32 dwFrameInterval;
+	__u16 wKeyFrameRate;
+	__u16 wPFrameRate;
+	__u16 wCompQuality;
+	__u16 wCompWindowSize;
+	__u16 wDelay;
+	__u32 dwMaxVideoFrameSize;
+	__u32 dwMaxPayloadTransferSize;
+	__u32 dwClockFrequency;
+	__u8  bmFramingInfo;
+	__u8  bPreferedVersion;
+	__u8  bMinVersion;
+	__u8  bMaxVersion;
+} __attribute__((__packed__));
+
+/* ------------------------------------------------------------------------
+ * Debugging, printing and logging
+ */
+
+#ifdef __KERNEL__
+
+#include <linux/usb.h>	/* For usb_endpoint_* */
+#include <linux/usb/gadget.h>
+#include <linux/videodev2.h>
+#include <media/v4l2-fh.h>
+
+#include "uvc_queue.h"
+
+#define UVC_TRACE_PROBE				(1 << 0)
+#define UVC_TRACE_DESCR				(1 << 1)
+#define UVC_TRACE_CONTROL			(1 << 2)
+#define UVC_TRACE_FORMAT			(1 << 3)
+#define UVC_TRACE_CAPTURE			(1 << 4)
+#define UVC_TRACE_CALLS				(1 << 5)
+#define UVC_TRACE_IOCTL				(1 << 6)
+#define UVC_TRACE_FRAME				(1 << 7)
+#define UVC_TRACE_SUSPEND			(1 << 8)
+#define UVC_TRACE_STATUS			(1 << 9)
+
+#define UVC_WARN_MINMAX				0
+#define UVC_WARN_PROBE_DEF			1
+
+extern unsigned int uvc_trace_param;
+
+#define uvc_trace(flag, msg...) \
+	do { \
+		if (uvc_trace_param & flag) \
+			printk(KERN_DEBUG "uvcvideo: " msg); \
+	} while (0)
+
+#define uvc_warn_once(dev, warn, msg...) \
+	do { \
+		if (!test_and_set_bit(warn, &dev->warnings)) \
+			printk(KERN_INFO "uvcvideo: " msg); \
+	} while (0)
+
+#define uvc_printk(level, msg...) \
+	printk(level "uvcvideo: " msg)
+
+/* ------------------------------------------------------------------------
+ * Driver specific constants
+ */
+
+#define DRIVER_VERSION				"0.1.0"
+#define DRIVER_VERSION_NUMBER			KERNEL_VERSION(0, 1, 0)
+
+#define DMA_ADDR_INVALID			(~(dma_addr_t)0)
+
+#define UVC_NUM_REQUESTS			4
+#define UVC_MAX_REQUEST_SIZE			64
+#define UVC_MAX_EVENTS				4
+
+#define USB_DT_INTERFACE_ASSOCIATION_SIZE	8
+#define USB_CLASS_MISC				0xef
+
+/* ------------------------------------------------------------------------
+ * Structures
+ */
+
+struct uvc_video
+{
+	struct usb_ep *ep;
+
+	/* Frame parameters */
+	u8 bpp;
+	u32 fcc;
+	unsigned int width;
+	unsigned int height;
+	unsigned int imagesize;
+
+	/* Requests */
+	unsigned int req_size;
+	struct usb_request *req[UVC_NUM_REQUESTS];
+	__u8 *req_buffer[UVC_NUM_REQUESTS];
+	struct list_head req_free;
+	spinlock_t req_lock;
+
+	void (*encode) (struct usb_request *req, struct uvc_video *video,
+			struct uvc_buffer *buf);
+
+	/* Context data used by the completion handler */
+	__u32 payload_size;
+	__u32 max_payload_size;
+
+	struct uvc_video_queue queue;
+	unsigned int fid;
+};
+
+enum uvc_state
+{
+	UVC_STATE_DISCONNECTED,
+	UVC_STATE_CONNECTED,
+	UVC_STATE_STREAMING,
+};
+
+struct uvc_device
+{
+	struct video_device *vdev;
+	enum uvc_state state;
+	struct usb_function func;
+	struct uvc_video video;
+
+	/* Descriptors */
+	struct {
+		const struct uvc_descriptor_header * const *control;
+		const struct uvc_descriptor_header * const *fs_streaming;
+		const struct uvc_descriptor_header * const *hs_streaming;
+	} desc;
+
+	unsigned int control_intf;
+	struct usb_ep *control_ep;
+	struct usb_request *control_req;
+	void *control_buf;
+
+	unsigned int streaming_intf;
+
+	/* Events */
+	unsigned int event_length;
+	unsigned int event_setup_out : 1;
+};
+
+static inline struct uvc_device *to_uvc(struct usb_function *f)
+{
+	return container_of(f, struct uvc_device, func);
+}
+
+struct uvc_file_handle
+{
+	struct v4l2_fh vfh;
+	struct uvc_video *device;
+};
+
+#define to_uvc_file_handle(handle) \
+	container_of(handle, struct uvc_file_handle, vfh)
+
+extern struct v4l2_file_operations uvc_v4l2_fops;
+
+/* ------------------------------------------------------------------------
+ * Functions
+ */
+
+extern int uvc_video_enable(struct uvc_video *video, int enable);
+extern int uvc_video_init(struct uvc_video *video);
+extern int uvc_video_pump(struct uvc_video *video);
+
+extern void uvc_endpoint_stream(struct uvc_device *dev);
+
+extern void uvc_function_connect(struct uvc_device *uvc);
+extern void uvc_function_disconnect(struct uvc_device *uvc);
+
+#endif /* __KERNEL__ */
+
+#endif /* _UVC_GADGET_H_ */
+

drivers/usb/gadget/uvc_queue.h

+#ifndef _UVC_QUEUE_H_
+#define _UVC_QUEUE_H_
+
+#ifdef __KERNEL__
+
+#include <linux/kernel.h>
+#include <linux/poll.h>
+#include <linux/videodev2.h>
+
+/* Maximum frame size in bytes, for sanity checking. */
+#define UVC_MAX_FRAME_SIZE	(16*1024*1024)
+/* Maximum number of video buffers. */
+#define UVC_MAX_VIDEO_BUFFERS	32
+
+/* ------------------------------------------------------------------------
+ * Structures.
+ */
+
+enum uvc_buffer_state {
+	UVC_BUF_STATE_IDLE	= 0,
+	UVC_BUF_STATE_QUEUED	= 1,
+	UVC_BUF_STATE_ACTIVE	= 2,
+	UVC_BUF_STATE_DONE	= 3,
+	UVC_BUF_STATE_ERROR	= 4,
+};
+
+struct uvc_buffer {
+	unsigned long vma_use_count;
+	struct list_head stream;
+
+	/* Touched by interrupt handler. */
+	struct v4l2_buffer buf;
+	struct list_head queue;
+	wait_queue_head_t wait;
+	enum uvc_buffer_state state;
+};
+
+#define UVC_QUEUE_STREAMING		(1 << 0)
+#define UVC_QUEUE_DISCONNECTED		(1 << 1)
+#define UVC_QUEUE_DROP_INCOMPLETE	(1 << 2)
+#define UVC_QUEUE_PAUSED		(1 << 3)
+
+struct uvc_video_queue {
+	enum v4l2_buf_type type;
+
+	void *mem;
+	unsigned int flags;
+	__u32 sequence;
+
+	unsigned int count;
+	unsigned int buf_size;
+	unsigned int buf_used;
+	struct uvc_buffer buffer[UVC_MAX_VIDEO_BUFFERS];
+	struct mutex mutex;	/* protects buffers and mainqueue */
+	spinlock_t irqlock;	/* protects irqqueue */
+
+	struct list_head mainqueue;
+	struct list_head irqqueue;
+};
+
+extern void uvc_queue_init(struct uvc_video_queue *queue,
+		enum v4l2_buf_type type);
+extern int uvc_alloc_buffers(struct uvc_video_queue *queue,
+		unsigned int nbuffers, unsigned int buflength);
+extern int uvc_free_buffers(struct uvc_video_queue *queue);
+extern int uvc_query_buffer(struct uvc_video_queue *queue,
+		struct v4l2_buffer *v4l2_buf);
+extern int uvc_queue_buffer(struct uvc_video_queue *queue,
+		struct v4l2_buffer *v4l2_buf);
+extern int uvc_dequeue_buffer(struct uvc_video_queue *queue,
+		struct v4l2_buffer *v4l2_buf, int nonblocking);
+extern int uvc_queue_enable(struct uvc_video_queue *queue, int enable);
+extern void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect);
+extern struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
+		struct uvc_buffer *buf);
+extern unsigned int uvc_queue_poll(struct uvc_video_queue *queue,
+		struct file *file, poll_table *wait);
+extern int uvc_queue_mmap(struct uvc_video_queue *queue,
+		struct vm_area_struct *vma);
+static inline int uvc_queue_streaming(struct uvc_video_queue *queue)
+{
+	return queue->flags & UVC_QUEUE_STREAMING;
+}
+extern struct uvc_buffer *uvc_queue_head(struct uvc_video_queue *queue);
+
+#endif /* __KERNEL__ */
+
+#endif /* _UVC_QUEUE_H_ */
+

drivers/usb/gadget/uvc_v4l2.c

+/*
+ *	uvc_v4l2.c  --  USB Video Class Gadget driver
+ *
+ *	Copyright (C) 2009-2010
+ *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/version.h>
+#include <linux/videodev2.h>
+#include <linux/vmalloc.h>
+#include <linux/wait.h>
+
+#include <media/v4l2-dev.h>
+#include <media/v4l2-event.h>
+#include <media/v4l2-ioctl.h>
+
+#include "uvc.h"
+#include "uvc_queue.h"
+
+/* --------------------------------------------------------------------------
+ * Requests handling
+ */
+
+static int
+uvc_send_response(struct uvc_device *uvc, struct uvc_request_data *data)
+{
+	struct usb_composite_dev *cdev = uvc->func.config->cdev;
+	struct usb_request *req = uvc->control_req;
+
+	if (data->length < 0)
+		return usb_ep_set_halt(cdev->gadget->ep0);
+
+	req->length = min(uvc->event_length, data->length);
+	req->zero = data->length < uvc->event_length;
+	req->dma = DMA_ADDR_INVALID;
+
+	memcpy(req->buf, data->data, data->length);
+
+	return usb_ep_queue(cdev->gadget->ep0, req, GFP_KERNEL);
+}
+
+/* --------------------------------------------------------------------------
+ * V4L2
+ */
+
+struct uvc_format
+{
+	u8 bpp;
+	u32 fcc;
+};
+
+static struct uvc_format uvc_formats[] = {
+	{ 16, V4L2_PIX_FMT_YUYV  },
+	{ 0,  V4L2_PIX_FMT_MJPEG },
+};
+
+static int
+uvc_v4l2_get_format(struct uvc_video *video, struct v4l2_format *fmt)
+{
+	fmt->fmt.pix.pixelformat = video->fcc;
+	fmt->fmt.pix.width = video->width;
+	fmt->fmt.pix.height = video->height;
+	fmt->fmt.pix.field = V4L2_FIELD_NONE;
+	fmt->fmt.pix.bytesperline = video->bpp * video->width / 8;
+	fmt->fmt.pix.sizeimage = video->imagesize;
+	fmt->fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
+	fmt->fmt.pix.priv = 0;
+
+	return 0;
+}
+
+static int
+uvc_v4l2_set_format(struct uvc_video *video, struct v4l2_format *fmt)
+{
+	struct uvc_format *format;
+	unsigned int imagesize;
+	unsigned int bpl;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(uvc_formats); ++i) {
+		format = &uvc_formats[i];
+		if (format->fcc == fmt->fmt.pix.pixelformat)
+			break;
+	}
+
+	if (format == NULL || format->fcc != fmt->fmt.pix.pixelformat) {
+		printk(KERN_INFO "Unsupported format 0x%08x.\n",
+			fmt->fmt.pix.pixelformat);
+		return -EINVAL;
+	}
+
+	bpl = format->bpp * fmt->fmt.pix.width / 8;
+	imagesize = bpl ? bpl * fmt->fmt.pix.height : fmt->fmt.pix.sizeimage;
+
+	video->fcc = format->fcc;
+	video->bpp = format->bpp;
+	video->width = fmt->fmt.pix.width;
+	video->height = fmt->fmt.pix.height;
+	video->imagesize = imagesize;
+
+	fmt->fmt.pix.field = V4L2_FIELD_NONE;
+	fmt->fmt.pix.bytesperline = bpl;
+	fmt->fmt.pix.sizeimage = imagesize;
+	fmt->fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
+	fmt->fmt.pix.priv = 0;
+
+	return 0;
+}
+
+static int
+uvc_v4l2_open(struct file *file)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct uvc_device *uvc = video_get_drvdata(vdev);
+	struct uvc_file_handle *handle;
+	int ret;
+
+	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
+	if (handle == NULL)
+		return -ENOMEM;
+
+	ret = v4l2_fh_init(&handle->vfh, vdev);
+	if (ret < 0)
+		goto error;
+
+	ret = v4l2_event_init(&handle->vfh);
+	if (ret < 0)
+		goto error;
+
+	ret = v4l2_event_alloc(&handle->vfh, 8);
+	if (ret < 0)
+		goto error;
+
+	v4l2_fh_add(&handle->vfh);
+
+	handle->device = &uvc->video;
+	file->private_data = &handle->vfh;
+
+	uvc_function_connect(uvc);
+	return 0;
+
+error:
+	v4l2_fh_exit(&handle->vfh);
+	return ret;
+}
+
+static int
+uvc_v4l2_release(struct file *file)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct uvc_device *uvc = video_get_drvdata(vdev);
+	struct uvc_file_handle *handle = to_uvc_file_handle(file->private_data);
+	struct uvc_video *video = handle->device;
+
+	uvc_function_disconnect(uvc);
+
+	uvc_video_enable(video, 0);
+	mutex_lock(&video->queue.mutex);
+	if (uvc_free_buffers(&video->queue) < 0)
+		printk(KERN_ERR "uvc_v4l2_release: Unable to free "
+				"buffers.\n");
+	mutex_unlock(&video->queue.mutex);
+
+	file->private_data = NULL;
+	v4l2_fh_del(&handle->vfh);
+	v4l2_fh_exit(&handle->vfh);
+	kfree(handle);
+	return 0;
+}
+
+static long
+uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct uvc_device *uvc = video_get_drvdata(vdev);
+	struct uvc_file_handle *handle = to_uvc_file_handle(file->private_data);
+	struct usb_composite_dev *cdev = uvc->func.config->cdev;
+	struct uvc_video *video = &uvc->video;
+	int ret = 0;
+
+	switch (cmd) {
+	/* Query capabilities */
+	case VIDIOC_QUERYCAP:
+	{
+		struct v4l2_capability *cap = arg;
+
+		memset(cap, 0, sizeof *cap);
+		strncpy(cap->driver, "g_uvc", sizeof(cap->driver));
+		strncpy(cap->card, cdev->gadget->name, sizeof(cap->card));
+		strncpy(cap->bus_info, dev_name(&cdev->gadget->dev),
+			sizeof cap->bus_info);
+		cap->version = DRIVER_VERSION_NUMBER;
+		cap->capabilities = V4L2_CAP_VIDEO_OUTPUT | V4L2_CAP_STREAMING;
+		break;
+	}
+
+	/* Get & Set format */
+	case VIDIOC_G_FMT:
+	{
+		struct v4l2_format *fmt = arg;
+
+		if (fmt->type != video->queue.type)
+			return -EINVAL;
+
+		return uvc_v4l2_get_format(video, fmt);
+	}
+
+	case VIDIOC_S_FMT:
+	{
+		struct v4l2_format *fmt = arg;
+
+		if (fmt->type != video->queue.type)
+			return -EINVAL;
+
+		return uvc_v4l2_set_format(video, fmt);
+	}
+
+	/* Buffers & streaming */
+	case VIDIOC_REQBUFS:
+	{
+		struct v4l2_requestbuffers *rb = arg;
+
+		if (rb->type != video->queue.type ||
+		    rb->memory != V4L2_MEMORY_MMAP)
+			return -EINVAL;
+
+		ret = uvc_alloc_buffers(&video->queue, rb->count,
+					video->imagesize);
+		if (ret < 0)
+			return ret;
+
+		rb->count = ret;
+		ret = 0;
+		break;
+	}
+
+	case VIDIOC_QUERYBUF:
+	{
+		struct v4l2_buffer *buf = arg;
+
+		if (buf->type != video->queue.type)
+			return -EINVAL;
+
+		return uvc_query_buffer(&video->queue, buf);
+	}
+
+	case VIDIOC_QBUF:
+		if ((ret = uvc_queue_buffer(&video->queue, arg)) < 0)
+			return ret;
+
+		return uvc_video_pump(video);
+
+	case VIDIOC_DQBUF:
+		return uvc_dequeue_buffer(&video->queue, arg,
+			file->f_flags & O_NONBLOCK);
+
+	case VIDIOC_STREAMON:
+	{
+		int *type = arg;
+
+		if (*type != video->queue.type)
+			return -EINVAL;
+
+		return uvc_video_enable(video, 1);
+	}
+
+	case VIDIOC_STREAMOFF:
+	{
+		int *type = arg;
+
+		if (*type != video->queue.type)
+			return -EINVAL;
+
+		return uvc_video_enable(video, 0);
+	}
+
+	/* Events */
+        case VIDIOC_DQEVENT:
+	{
+		struct v4l2_event *event = arg;
+
+		ret = v4l2_event_dequeue(&handle->vfh, event,
+					 file->f_flags & O_NONBLOCK);
+		if (ret == 0 && event->type == UVC_EVENT_SETUP) {
+			struct uvc_event *uvc_event = (void *)&event->u.data;
+
+			/* Tell the complete callback to generate an event for
+			 * the next request that will be enqueued by
+			 * uvc_event_write.
+			 */
+			uvc->event_setup_out =
+				!(uvc_event->req.bRequestType & USB_DIR_IN);
+			uvc->event_length = uvc_event->req.wLength;
+		}
+
+		return ret;
+	}
+
+	case VIDIOC_SUBSCRIBE_EVENT:
+	{
+		struct v4l2_event_subscription *sub = arg;
+
+		if (sub->type < UVC_EVENT_FIRST || sub->type > UVC_EVENT_LAST)
+			return -EINVAL;
+
+		return v4l2_event_subscribe(&handle->vfh, arg);
+	}
+
+	case VIDIOC_UNSUBSCRIBE_EVENT:
+		return v4l2_event_unsubscribe(&handle->vfh, arg);
+
+	case UVCIOC_SEND_RESPONSE:
+		ret = uvc_send_response(uvc, arg);
+		break;
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return ret;
+}
+
+static long
+uvc_v4l2_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	return video_usercopy(file, cmd, arg, uvc_v4l2_do_ioctl);
+}
+
+static int
+uvc_v4l2_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct uvc_device *uvc = video_get_drvdata(vdev);
+
+	return uvc_queue_mmap(&uvc->video.queue, vma);
+}
+
+static unsigned int
+uvc_v4l2_poll(struct file *file, poll_table *wait)
+{
+	struct video_device *vdev = video_devdata(file);
+	struct uvc_device *uvc = video_get_drvdata(vdev);
+	struct uvc_file_handle *handle = to_uvc_file_handle(file->private_data);
+	unsigned int mask = 0;
+
+	poll_wait(file, &handle->vfh.events->wait, wait);
+	if (v4l2_event_pending(&handle->vfh))
+		mask |= POLLPRI;
+
+	mask |= uvc_queue_poll(&uvc->video.queue, file, wait);
+
+	return mask;
+}
+
+struct v4l2_file_operations uvc_v4l2_fops = {
+	.owner		= THIS_MODULE,
+	.open		= uvc_v4l2_open,
+	.release	= uvc_v4l2_release,
+	.ioctl		= uvc_v4l2_ioctl,
+	.mmap		= uvc_v4l2_mmap,
+	.poll		= uvc_v4l2_poll,
+};
+

drivers/usb/gadget/uvc_video.c

+/*
+ *	uvc_video.c  --  USB Video Class Gadget driver
+ *
+ *	Copyright (C) 2009-2010
+ *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/gadget.h>
+
+#include <media/v4l2-dev.h>
+
+#include "uvc.h"
+#include "uvc_queue.h"
+
+/* --------------------------------------------------------------------------
+ * Video codecs
+ */
+
+static int
+uvc_video_encode_header(struct uvc_video *video, struct uvc_buffer *buf,
+		u8 *data, int len)
+{
+	data[0] = 2;
+	data[1] = UVC_STREAM_EOH | video->fid;
+
+	if (buf->buf.bytesused - video->queue.buf_used <= len - 2)
+		data[1] |= UVC_STREAM_EOF;
+
+	return 2;
+}
+
+static int
+uvc_video_encode_data(struct uvc_video *video, struct uvc_buffer *buf,
+		u8 *data, int len)
+{
+	struct uvc_video_queue *queue = &video->queue;
+	unsigned int nbytes;
+	void *mem;
+
+	/* Copy video data to the USB buffer. */
+	mem = queue->mem + buf->buf.m.offset + queue->buf_used;
+	nbytes = min((unsigned int)len, buf->buf.bytesused - queue->buf_used);
+
+	memcpy(data, mem, nbytes);
+	queue->buf_used += nbytes;
+
+	return nbytes;
+}
+
+static void
+uvc_video_encode_bulk(struct usb_request *req, struct uvc_video *video,
+		struct uvc_buffer *buf)
+{
+	void *mem = req->buf;
+	int len = video->req_size;
+	int ret;
+
+	/* Add a header at the beginning of the payload. */
+	if (video->payload_size == 0) {
+		ret = uvc_video_encode_header(video, buf, mem, len);
+		video->payload_size += ret;
+		mem += ret;
+		len -= ret;
+	}
+
+	/* Process video data. */
+	len = min((int)(video->max_payload_size - video->payload_size), len);
+	ret = uvc_video_encode_data(video, buf, mem, len);
+
+	video->payload_size += ret;
+	len -= ret;
+
+	req->length = video->req_size - len;
+	req->zero = video->payload_size == video->max_payload_size;
+
+	if (buf->buf.bytesused == video->queue.buf_used) {
+		video->queue.buf_used = 0;
+		buf->state = UVC_BUF_STATE_DONE;
+		uvc_queue_next_buffer(&video->queue, buf);
+		video->fid ^= UVC_STREAM_FID;
+
+		video->payload_size = 0;
+	}
+
+	if (video->payload_size == video->max_payload_size ||
+	    buf->buf.bytesused == video->queue.buf_used)
+		video->payload_size = 0;
+}
+
+static void
+uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
+		struct uvc_buffer *buf)
+{
+	void *mem = req->buf;
+	int len = video->req_size;
+	int ret;
+
+	/* Add the header. */
+	ret = uvc_video_encode_header(video, buf, mem, len);
+	mem += ret;
+	len -= ret;
+
+	/* Process video data. */
+	ret = uvc_video_encode_data(video, buf, mem, len);
+	len -= ret;
+
+	req->length = video->req_size - len;
+
+	if (buf->buf.bytesused == video->queue.buf_used) {
+		video->queue.buf_used = 0;
+		buf->state = UVC_BUF_STATE_DONE;
+		uvc_queue_next_buffer(&video->queue, buf);
+		video->fid ^= UVC_STREAM_FID;
+	}
+}
+
+/* --------------------------------------------------------------------------
+ * Request handling
+ */
+
+/*
+ * I somehow feel that synchronisation won't be easy to achieve here. We have
+ * three events that control USB requests submission:
+ *
+ * - USB request completion: the completion handler will resubmit the request
+ *   if a video buffer is available.
+ *
+ * - USB interface setting selection: in response to a SET_INTERFACE request,
+ *   the handler will start streaming if a video buffer is available and if
+ *   video is not currently streaming.
+ *
+ * - V4L2 buffer queueing: the driver will start streaming if video is not
+ *   currently streaming.
+ *
+ * Race conditions between those 3 events might lead to deadlocks or other
+ * nasty side effects.
+ *
+ * The "video currently streaming" condition can't be detected by the irqqueue
+ * being empty, as a request can still be in flight. A separate "queue paused"
+ * flag is thus needed.
+ *
+ * The paused flag will be set when we try to retrieve the irqqueue head if the
+ * queue is empty, and cleared when we queue a buffer.
+ *
+ * The USB request completion handler will get the buffer at the irqqueue head
+ * under protection of the queue spinlock. If the queue is empty, the streaming
+ * paused flag will be set. Right after releasing the spinlock a userspace
+ * application can queue a buffer. The flag will then cleared, and the ioctl
+ * handler will restart the video stream.
+ */
+static void
+uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct uvc_video *video = req->context;
+	struct uvc_buffer *buf;
+	unsigned long flags;
+	int ret;
+
+	switch (req->status) {
+	case 0:
+		break;
+
+	case -ESHUTDOWN:
+		printk(KERN_INFO "VS request cancelled.\n");
+		goto requeue;
+
+	default:
+		printk(KERN_INFO "VS request completed with status %d.\n",
+			req->status);
+		goto requeue;
+	}
+
+	spin_lock_irqsave(&video->queue.irqlock, flags);
+	buf = uvc_queue_head(&video->queue);
+	if (buf == NULL) {
+		spin_unlock_irqrestore(&video->queue.irqlock, flags);
+		goto requeue;
+	}
+
+	video->encode(req, video, buf);
+
+	if ((ret = usb_ep_queue(ep, req, GFP_ATOMIC)) < 0) {
+		printk(KERN_INFO "Failed to queue request (%d).\n", ret);
+		usb_ep_set_halt(ep);
+		spin_unlock_irqrestore(&video->queue.irqlock, flags);
+		goto requeue;
+	}
+	spin_unlock_irqrestore(&video->queue.irqlock, flags);
+
+	return;
+
+requeue:
+	spin_lock_irqsave(&video->req_lock, flags);
+	list_add_tail(&req->list, &video->req_free);
+	spin_unlock_irqrestore(&video->req_lock, flags);
+}
+
+static int
+uvc_video_free_requests(struct uvc_video *video)
+{
+	unsigned int i;
+
+	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
+		if (video->req[i]) {
+			usb_ep_free_request(video->ep, video->req[i]);
+			video->req[i] = NULL;
+		}
+
+		if (video->req_buffer[i]) {
+			kfree(video->req_buffer[i]);
+			video->req_buffer[i] = NULL;
+		}
+	}
+
+	INIT_LIST_HEAD(&video->req_free);
+	video->req_size = 0;
+	return 0;
+}
+
+static int
+uvc_video_alloc_requests(struct uvc_video *video)
+{
+	unsigned int i;
+	int ret = -ENOMEM;
+
+	BUG_ON(video->req_size);
+
+	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
+		video->req_buffer[i] = kmalloc(video->ep->maxpacket, GFP_KERNEL);
+		if (video->req_buffer[i] == NULL)
+			goto error;
+
+		video->req[i] = usb_ep_alloc_request(video->ep, GFP_KERNEL);
+		if (video->req[i] == NULL)
+			goto error;
+
+		video->req[i]->buf = video->req_buffer[i];
+		video->req[i]->length = 0;
+		video->req[i]->dma = DMA_ADDR_INVALID;
+		video->req[i]->complete = uvc_video_complete;
+		video->req[i]->context = video;
+
+		list_add_tail(&video->req[i]->list, &video->req_free);
+	}
+
+	video->req_size = video->ep->maxpacket;
+	return 0;
+
+error:
+	uvc_video_free_requests(video);
+	return ret;
+}
+
+/* --------------------------------------------------------------------------
+ * Video streaming
+ */
+
+/*
+ * uvc_video_pump - Pump video data into the USB requests
+ *
+ * This function fills the available USB requests (listed in req_free) with
+ * video data from the queued buffers.
+ */
+int
+uvc_video_pump(struct uvc_video *video)
+{
+	struct usb_request *req;
+	struct uvc_buffer *buf;
+	unsigned long flags;
+	int ret;
+
+	/* FIXME TODO Race between uvc_video_pump and requests completion
+	 * handler ???
+	 */
+
+	while (1) {
+		/* Retrieve the first available USB request, protected by the
+		 * request lock.
+		 */
+		spin_lock_irqsave(&video->req_lock, flags);
+		if (list_empty(&video->req_free)) {
+			spin_unlock_irqrestore(&video->req_lock, flags);
+			return 0;
+		}
+		req = list_first_entry(&video->req_free, struct usb_request,
+					list);
+		list_del(&req->list);
+		spin_unlock_irqrestore(&video->req_lock, flags);
+
+		/* Retrieve the first available video buffer and fill the
+		 * request, protected by the video queue irqlock.
+		 */
+		spin_lock_irqsave(&video->queue.irqlock, flags);
+		buf = uvc_queue_head(&video->queue);
+		if (buf == NULL) {
+			spin_unlock_irqrestore(&video->queue.irqlock, flags);
+			break;
+		}
+
+		video->encode(req, video, buf);
+
+		/* Queue the USB request */
+		if ((ret = usb_ep_queue(video->ep, req, GFP_KERNEL)) < 0) {
+			printk(KERN_INFO "Failed to queue request (%d)\n", ret);
+			usb_ep_set_halt(video->ep);
+			spin_unlock_irqrestore(&video->queue.irqlock, flags);
+			break;
+		}
+		spin_unlock_irqrestore(&video->queue.irqlock, flags);
+	}
+
+	spin_lock_irqsave(&video->req_lock, flags);
+	list_add_tail(&req->list, &video->req_free);
+	spin_unlock_irqrestore(&video->req_lock, flags);
+	return 0;
+}
+
+/*
+ * Enable or disable the video stream.
+ */
+int
+uvc_video_enable(struct uvc_video *video, int enable)
+{
+	unsigned int i;
+	int ret;
+
+	if (video->ep == NULL) {
+		printk(KERN_INFO "Video enable failed, device is "
+			"uninitialized.\n");
+		return -ENODEV;
+	}
+
+	if (!enable) {
+		for (i = 0; i < UVC_NUM_REQUESTS; ++i)
+			usb_ep_dequeue(video->ep, video->req[i]);
+
+		uvc_video_free_requests(video);
+		uvc_queue_enable(&video->queue, 0);
+		return 0;
+	}
+
+	if ((ret = uvc_queue_enable(&video->queue, 1)) < 0)
+		return ret;
+
+	if ((ret = uvc_video_alloc_requests(video)) < 0)
+		return ret;
+
+	if (video->max_payload_size) {
+		video->encode = uvc_video_encode_bulk;
+		video->payload_size = 0;
+	} else
+		video->encode = uvc_video_encode_isoc;
+
+	return uvc_video_pump(video);
+}
+
+/*
+ * Initialize the UVC video stream.
+ */
+int
+uvc_video_init(struct uvc_video *video)
+{
+	INIT_LIST_HEAD(&video->req_free);
+	spin_lock_init(&video->req_lock);
+
+	video->fcc = V4L2_PIX_FMT_YUYV;
+	video->bpp = 16;
+	video->width = 320;
+	video->height = 240;
+	video->imagesize = 320 * 240 * 2;
+
+	/* Initialize the video buffers queue. */
+	uvc_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT);
+	return 0;
+}
+