uvc摄像头代码解析7

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13.uvc视频初始化

13.1 uvc数据流控制

[cpp

struct uvc_streaming_control {

__u16 bmHint;

__u8 bFormatIndex; //视频格式索引

__u8 bFrameIndex; //视频帧索引

__u32 dwFrameInterval; //视频帧间隔

__u16 wKeyFrameRate; //

__u16 wPFrameRate;

__u16 wCompQuality;

__u16 wCompWindowSize;

__u16 wDelay; //延时

__u32 dwMaxVideoFrameSize; //最大视频帧大小

__u32 dwMaxPayloadTransferSize;

__u32 dwClockFrequency; //时钟频率

__u8 bmFramingInfo;

__u8 bPreferedVersion;

__u8 bMinVersion; //版本

__u8 bMaxVersion; //版本

} __attribute__((__packed__));

13.2 uvc_video_init

[cpp]

int uvc_video_init(struct uvc_streaming *stream)

{

struct uvc_streaming_control *probe = &stream->ctrl; //获取uvc数据流的uvs数据流控制对象

struct uvc_format *format = NULL;

struct uvc_frame *frame = NULL;

unsigned int i;

int ret;

if (stream->nformats == 0) {

uvc_printk(KERN_INFO, "No supported video formats found.\n");

return -EINVAL;

}

atomic_set(&stream->active, 0);

uvc_queue_init(&stream->queue, stream->type, !uvc_no_drop_param); //初始化视频缓冲区队列

usb_set_interface(stream->dev->udev, stream->intfnum, 0); //选择Alt.Setting 0

if (uvc_get_video_ctrl(stream, probe, 1, UVC_GET_DEF) == 0) //VS_PROBE_CONTROL(GET_DEF)

uvc_set_video_ctrl(stream, probe, 1); //VS_PROBE_CONTROL(SET_DEF)

ret = uvc_get_video_ctrl(stream, probe, 1, UVC_GET_CUR); //VS_PROBE_CONTROL(GET_CUR)

if (ret < 0)

return ret;

for (i = stream->nformats; i > 0; --i) { //获取对应的uvc格式

format = &stream->format[i-1];

if (format->index == probe->bFormatIndex) //匹配uvc格式索引值

break;

}

if (format->nframes == 0) {

uvc_printk(KERN_INFO, "No frame descriptor found for the default format.\n");

return -EINVAL;

}

for (i = format->nframes; i > 0; --i) {

frame = &format->frame[i-1]; //获取对应的uvc帧

if (frame->bFrameIndex == probe->bFrameIndex) //匹配uvc帧索引值

break;

}

probe->bFormatIndex = format->index; //设置uvc视频流控制的格式索引为uvc格式的索引

probe->bFrameIndex = frame->bFrameIndex; //设置uvc视频流控制的帧索引为uvc帧的索引

stream->cur_format = format; //设置uvc格式为uvc数据流的cur_format成员

stream->cur_frame = frame; //设置uvc帧未uvc数据流的cur_frame成员

/* Select the video decoding function 选择视频解码函数*/

if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) { //视频采集

if (stream->dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)

stream->decode = uvc_video_decode_isight;

else if (stream->intf->num_altsetting > 1)

stream->decode = uvc_video_decode_isoc; //同步方式

else

stream->decode = uvc_video_decode_bulk; //bluk方式

}

else { //视频播放

if (stream->intf->num_altsetting == 1)

stream->decode = uvc_video_encode_bulk;

else {

uvc_printk(KERN_INFO, "Isochronous endpoints are not supported for video output devices.\n");

return -EINVAL;

}

return 0;

}

13.2.1 初始化uvc队列

[cpp]

void uvc_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,int drop_corrupted)

{

mutex_init(&queue->mutex);

spin_lock_init(&queue->irqlock);

INIT_LIST_HEAD(&queue->mainqueue); //初始化uvc视频队列mainqueue链表

INIT_LIST_HEAD(&queue->irqqueue); //初始化uvc视频队列irqqueue链表

queue->flags = drop_corrupted ? UVC_QUEUE_DROP_CORRUPTED : 0;

queue->type = type;

}

14.uvc V4L2设备

14.1 V4L2操作函数集

[cpp]

const struct v4l2_file_operations uvc_fops = {

.owner = THIS_MODULE,

.open = uvc_v4l2_open, //打开方法

.release = uvc_v4l2_release, //释放方法

.unlocked_ioctl = uvc_v4l2_ioctl, //控制方法

.read = uvc_v4l2_read, //读方法

.mmap = uvc_v4l2_mmap, //映射方法

.poll = uvc_v4l2_poll, //轮询方法

};

14.2 打开方法

14.2.1 相关结构体

[cpp]

struct uvc_fh {//uvc句柄

struct uvc_video_chain *chain; //uvc视频链

struct uvc_streaming *stream; //uvc视频流

enum uvc_handle_state state;

};

14.2.2 open

[cpp]

static int uvc_v4l2_open(struct file *file)

{

struct uvc_streaming *stream;

struct uvc_fh *handle;

int ret = 0;

uvc_trace(UVC_TRACE_CALLS, "uvc_v4l2_open\n");

stream = video_drvdata(file); //获取uvc视频流

if (stream->dev->state & UVC_DEV_DISCONNECTED) //设备没连接

return -ENODEV;

ret = usb_autopm_get_interface(stream->dev->intf); //唤醒设备

if (ret < 0)

return ret;

/* Create the device handle. */

handle = kzalloc(sizeof *handle, GFP_KERNEL); //创建uvc句柄

if (handle == NULL) {

usb_autopm_put_interface(stream->dev->intf);

return -ENOMEM;

}

if (atomic_inc_return(&stream->dev->users) == 1) {

ret = uvc_status_start(stream->dev); //uvc状态开始

if (ret < 0) {

usb_autopm_put_interface(stream->dev->intf);

atomic_dec(&stream->dev->users);

kfree(handle);

return ret;

}

handle->chain = stream->chain; //捆绑uvc句柄和uvc视频链

handle->stream = stream; //捆绑uvc句柄和uvc视频流

handle->state = UVC_HANDLE_PASSIVE; //设置uvc状态为未激活

file->private_data = handle; //将uvc句柄作为文件的私有数据

return 0;

}

14.2.2.1 uvc_status_start启动状态

[cpp]

int uvc_status_start(struct uvc_device *dev)

{

if (dev->int_urb == NULL)

return 0;

return usb_submit_urb(dev->int_urb, GFP_KERNEL); //提交urb

}

参看 12.uvc状态初始化

14.3 控制方法

14.3.1 V4L2的控制方式可以参考下面的资料

linux媒体接口API

常用的命令

[cpp]

VIDIOC_REQBUFS：分配内存

VIDIOC_QUERYBUF：把VIDIOC_REQBUFS中分配的数据缓存转换成物理地址

VIDIOC_QUERYCAP：查询驱动功能

VIDIOC_ENUM_FMT：获取当前驱动支持的视频格式

VIDIOC_S_FMT：设置当前驱动的频捕获格式

VIDIOC_G_FMT：读取当前驱动的频捕获格式

VIDIOC_TRY_FMT：验证当前驱动的显示格式

VIDIOC_CROPCAP：查询驱动的修剪能力

VIDIOC_S_CROP：设置视频信号的边框

VIDIOC_G_CROP：读取视频信号的边框

VIDIOC_QBUF：把数据从缓存中读取出来

VIDIOC_DQBUF：把数据放回缓存队列

VIDIOC_STREAMON：开始视频显示函数

VIDIOC_STREAMOFF：结束视频显示函数

VIDIOC_QUERYSTD：检查当前视频设备支持的标准，例如PAL或NTSC。

14.3.2 uvc设备V4L2控制方法uvc_v4l2_do_ioctl

[cpp]

static long uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)

{

struct video_device *vdev = video_devdata(file);//获取V4L2设备

struct uvc_fh *handle = file->private_data;//获取uvc句柄

struct uvc_video_chain *chain = handle->chain;//获取uvc视频链

struct uvc_streaming *stream = handle->stream;//获取uvc视频流

long ret = 0;

switch (cmd) {

...

case ...:

{

...

break;

}

return ret;

}

a.VIDIOC_STREAMON 开始视频显示函数

[cpp]

<pre class="cpp" name="code"> case VIDIOC_STREAMON:

{

int *type = arg;

if (*type != stream->type)

return -EINVAL;

if (!uvc_has_privileges(handle))

return -EBUSY;

mutex_lock(&stream->mutex);

ret = uvc_video_enable(stream, 1); //uvc视频流使能

mutex_unlock(&stream->mutex);

if (ret < 0)

return ret;

break;

}</pre>a.1 uvc视频流使能

<pre class="cpp" name="code">int uvc_video_enable(struct uvc_streaming *stream, int enable)

{

int ret;

if (!enable) {

uvc_uninit_video(stream, 1);//逆初始化视频

usb_set_interface(stream->dev->udev, stream->intfnum, 0);

uvc_queue_enable(&stream->queue, 0);//uvc禁用队列

return 0;

}

ret = uvc_queue_enable(&stream->queue, 1); //uvc使能队列

if (ret < 0)

return ret;

/* Commit the streaming parameters. */

ret = uvc_commit_video(stream, &stream->ctrl); //uvc提交视频参数

if (ret < 0)

return ret;

return uvc_init_video(stream, GFP_KERNEL); //uvc初始化视频

}</pre>a.1.1 uvc使能队列

<pre class="cpp" name="code"><pre class="cpp" name="code">static int uvc_queue_enable(struct uvc_video_queue *queue, int enable)

{

unsigned int i;

int ret = 0;

mutex_lock(&queue->mutex);

if (enable) { //使能uvc队列

if (uvc_queue_streaming(queue)) { //判断队列标志是否为UVC_QUEUE_STREAMING

ret = -EBUSY;

goto done;

}

queue->sequence = 0;

queue->flags |= UVC_QUEUE_STREAMING; //设置队列标志

queue->buf_used = 0; //设置缓冲区使用标志

}

else {

uvc_queue_cancel(queue, 0); //取消uvc队列

INIT_LIST_HEAD(&queue->mainqueue); //重新初始化uvc队列mainqueue队列头

for (i = 0; i < queue->count; ++i)

queue->buffer[i].state = UVC_BUF_STATE_IDLE; //设置缓冲区状态为闲置态

queue->flags &= ~UVC_QUEUE_STREAMING; //设置队列标志

}

done:

mutex_unlock(&queue->mutex);

return ret;

}</pre>a.1.2 uvc提交视频参数

<pre class="cpp" name="code"><pre class="cpp" name="code">int uvc_commit_video(struct uvc_streaming *stream,struct uvc_streaming_control *probe)

{

return uvc_set_video_ctrl(stream, probe, 0); //uvc设置视频控制

}</pre>a.1.3 uvc初始化视频

<pre class="cpp" name="code"><pre class="cpp" name="code">static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)

{

struct usb_interface *intf = stream->intf;

struct usb_host_endpoint *ep;

unsigned int i;

int ret;

stream->sequence = -1;

stream->last_fid = -1;

stream->bulk.header_size = 0;

stream->bulk.skip_payload = 0;

stream->bulk.payload_size = 0;

if (intf->num_altsetting > 1) { //同步方式

struct usb_host_endpoint *best_ep = NULL;

unsigned int best_psize = 3 * 1024;

unsigned int bandwidth;

unsigned int uninitialized_var(altsetting);

int intfnum = stream->intfnum;

/* Isochronous endpoint, select the alternate setting. */

bandwidth = stream->ctrl.dwMaxPayloadTransferSize;

if (bandwidth == 0) {

uvc_trace(UVC_TRACE_VIDEO, "Device requested null bandwidth, defaulting to lowest.\n");

bandwidth = 1;

}

else {

uvc_trace(UVC_TRACE_VIDEO, "Device requested %u B/frame bandwidth.\n", bandwidth);

}

for (i = 0; i < intf->num_altsetting; ++i) {

struct usb_host_interface *alts;

unsigned int psize;

alts = &intf->altsetting[i];

ep = uvc_find_endpoint(alts,stream->header.bEndpointAddress);

if (ep == NULL)

continue;

/* Check if the bandwidth is high enough. */

psize = le16_to_cpu(ep->desc.wMaxPacketSize);

psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));

if (psize >= bandwidth && psize <= best_psize) {

altsetting = i;

best_psize = psize;

best_ep = ep;

}

if (best_ep == NULL) {

uvc_trace(UVC_TRACE_VIDEO, "No fast enough alt setting for requested bandwidth.\n");

return -EIO;

}

uvc_trace(UVC_TRACE_VIDEO, "Selecting alternate setting %u (%u B/frame bandwidth).\n", altsetting, best_psize);

ret = usb_set_interface(stream->dev->udev, intfnum, altsetting);

if (ret < 0)

return ret;

ret = uvc_init_video_isoc(stream, best_ep, gfp_flags); //uvc初始化视频(同步方法)

}

else { //Bulk方式

/* Bulk endpoint, proceed to URB initialization. */

ep = uvc_find_endpoint(&intf->altsetting[0],stream->header.bEndpointAddress);

if (ep == NULL)

return -EIO;

ret = uvc_init_video_bulk(stream, ep, gfp_flags); //uvc初始化视频(bulk方法)

}

if (ret < 0)

return ret;

/* Submit the URBs. */

for (i = 0; i < UVC_URBS; ++i) {

ret = usb_submit_urb(stream->urb[i], gfp_flags); //提交urb

if (ret < 0) {

uvc_printk(KERN_ERR, "Failed to submit URB %u (%d).\n", i, ret);

uvc_uninit_video(stream, 1);

return ret;

}

return 0;

}</pre>a.1.3.1 同步方式

<pre class="cpp" name="code"><pre class="cpp" name="code">static int uvc_init_video_isoc(struct uvc_streaming *stream,struct usb_host_endpoint *ep, gfp_t gfp_flags)

{

struct urb *urb;

unsigned int npackets, i, j;

u16 psize;

u32 size;

psize = le16_to_cpu(ep->desc.wMaxPacketSize);

psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));

size = stream->ctrl.dwMaxVideoFrameSize;

npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags); //分配urb缓冲区

if (npackets == 0)

return -ENOMEM;

size = npackets * psize;

for (i = 0; i < UVC_URBS; ++i) {

urb = usb_alloc_urb(npackets, gfp_flags); //分配urb

if (urb == NULL) {

uvc_uninit_video(stream, 1);

return -ENOMEM;

}

urb->dev = stream->dev->udev; //设置urb

urb->context = stream;

urb->pipe = usb_rcvisocpipe(stream->dev->udev,ep->desc.bEndpointAddress);

urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;

urb->interval = ep->desc.bInterval;

urb->transfer_buffer = stream->urb_buffer[i];

urb->transfer_dma = stream->urb_dma[i];

urb->complete = uvc_video_complete;

urb->number_of_packets = npackets;

urb->transfer_buffer_length = size;

for (j = 0; j < npackets; ++j) {

urb->iso_frame_desc[j].offset = j * psize;

urb->iso_frame_desc[j].length = psize;

}

stream->urb[i] = urb;

}

return 0;

}</pre>a.1.3.2 Bluk方式

<pre class="cpp" name="code"><pre class="cpp" name="code">static int uvc_init_video_bulk(struct uvc_streaming *stream,struct usb_host_endpoint *ep, gfp_t gfp_flags)

{

struct urb *urb;

unsigned int npackets, pipe, i;

u16 psize;

u32 size;

psize = le16_to_cpu(ep->desc.wMaxPacketSize) & 0x07ff;

size = stream->ctrl.dwMaxPayloadTransferSize;

stream->bulk.max_payload_size = size;

npackets = uvc_alloc_urb_buffers(stream, size, psize, gfp_flags); //分配urb缓冲区

if (npackets == 0)

return -ENOMEM;

size = npackets * psize;

if (usb_endpoint_dir_in(&ep->desc))

pipe = usb_rcvbulkpipe(stream->dev->udev,ep->desc.bEndpointAddress);

else

pipe = usb_sndbulkpipe(stream->dev->udev,ep->desc.bEndpointAddress);

if (stream->type == V4L2_BUF_TYPE_VIDEO_OUTPUT)

size = 0;

for (i = 0; i < UVC_URBS; ++i) {

urb = usb_alloc_urb(0, gfp_flags); //分配urb

if (urb == NULL) {

uvc_uninit_video(stream, 1);

return -ENOMEM;

}

usb_fill_bulk_urb(urb, stream->dev->udev, pipe,stream->urb_buffer[i], size, uvc_video_complete,stream); //设置urb

urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;

urb->transfer_dma = stream->urb_dma[i];

stream->urb[i] = urb;

}

return 0;

}</pre><pre class="cpp" name="code"><pre class="cpp" name="code">a.1.3.1 同步方式和a.1.3.2 Bluk方式两种方式初始化uvc视频主要是分配设置urb,然后在uvc_init_video函数中又通过usb_submit_urb提交了urb,</pre><pre class="cpp" name="code">两种方法的urb回调函数都是uvc_video_complete</pre><pre class="cpp" name="code">a.2 urb回调函数uvc_video_complete</pre><pre class="cpp" name="code"><pre class="cpp" name="code">static void uvc_video_complete(struct urb *urb)

{

struct uvc_streaming *stream = urb->context;

struct uvc_video_queue *queue = &stream->queue;

struct uvc_buffer *buf = NULL;

unsigned long flags;

int ret;

switch (urb->status) {

case 0:

break;

default:

uvc_printk(KERN_WARNING, "Non-zero status (%d) in video completion handler.\n", urb->status);

case -ENOENT: /* usb_kill_urb() called. */

if (stream->frozen)

return;

case -ECONNRESET: /* usb_unlink_urb() called. */

case -ESHUTDOWN: /* The endpoint is being disabled. */

uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);

return;

}

spin_lock_irqsave(&queue->irqlock, flags);

if (!list_empty(&queue->irqqueue))

buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,queue);

spin_unlock_irqrestore(&queue->irqlock, flags);

stream->decode(urb, stream, buf); //调用uvc视频流的decode方法

if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) { //再次提交urb

uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",ret);

}

}</pre>对于同步和bilk方式的decode方法分别是

<pre class="cpp" name="code"> stream->decode = uvc_video_decode_isoc

stream->decode = uvc_video_encode_bulk;

这个在前面uvc_video_init函数中设置了</pre>

ok后面就开始解码了

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