title: 完整注释的代码摘录
date: 2019/4/23 20:40:00
toc: true
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完整注释的代码摘录

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#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <asm/atomic.h>
#include <asm/unaligned.h>#include <media/v4l2-common.h>
#include <media/v4l2-ioctl.h>
#include <media/videobuf-core.h>#include "uvcvideo.h"/* 参考 drivers/media/video/uvc目录下面的一系列文件 */#define MYUVC_URBS 5/* 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)/* 从Uvcvideo.h (drivers\media\video\uvc)拷贝过来* 这个结构体是和usb设备进行数据传输的结构体，我们可以从usb设备中获取这个结构体的信息，* 也可以自己填写这个结构体然后发送给usb设备，对usb设备进行设置。* 我们只需要使用usb_control_msg函数来发起usb数据的收发信号即可。* 这个结构体中的成员都是从uvc规格中Control Selector描述符中的位域名*/struct myuvc_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;
};struct frame_desc {int width;int height;
};/* 参考uvc_video_queue定义一些结构体 */
struct myuvc_buffer {
/* 必须要有v4l2_buffer，因为在以后的myuvc_vidioc_dqbuf和myuvc_vidioc_qbuf都需要这个结构体 */struct v4l2_buffer buf;int state;/* 表示是否已经被mmap，初始值为0 表示还没有被mmap，没经过mmap一次，就会被加1*/int vma_use_count; wait_queue_head_t wait;  /* APP要读某个缓冲区,如果无数据,在此休眠 */struct list_head stream;struct list_head irq;
};struct myuvc_queue {void *mem;  /* 所有的缓存都是这一整块内存，一整块的内存起始地址 */int count;  /* 缓冲区的个数 */int buf_size;   /* 缓冲区的大小 */ struct myuvc_buffer buffer[32];struct urb *urb[32];char *urb_buffer[32];/* urb buffer的物理地址 */dma_addr_t urb_dma[32];unsigned int urb_size;/* 供APP消费用，当这个队列中有数据时，应用程序会从这个队列中取出缓冲区 */struct list_head mainqueue;   /* 供底层驱动生产用，当摄像头产生数据时会将数据放入这个队列中的个缓存 */struct list_head irqqueue;
};static struct myuvc_queue myuvc_queue;static struct video_device *myuvc_vdev;
static struct usb_device *myuvc_udev;
/* 在开始函数中使用usb_set_interface函数设置了VS接口中的第8个bAlternateSetting，* 该bAlternateSetting中的端点地址bEndpointAddress为0x81，由描述符可知。*/
static int myuvc_bEndpointAddress = 0x81;
static int myuvc_streaming_intf;
static int myuvc_control_intf;
static int myuvc_streaming_bAlternateSetting = 8;
static struct v4l2_format myuvc_format;/* 这些分辨率是根据5个VS_FRAME_UNCOMPRESSED描述符写出来的 */
static struct frame_desc frames[] = {{640, 480}, {352, 288}, {320, 240}, {176, 144}, {160, 120}};
//分辨率的索引值
static int frame_idx = 1;
/* 每个像素多少位是在VS_FORMAT_UNCOMPRESSED格式描述符中的bBitsPerPixel表示 */
static int bBitsPerPixel = 16; /* lsusb -v -d 0x1e4e:  "bBitsPerPixel" */
static int uvc_version = 0x0100; /* lsusb -v -d 0x1e4e: bcdUVC */static int wMaxPacketSize = 1024;
static int ProcessingUnitID = 3;static struct myuvc_streaming_control myuvc_params;/* A2 参考 uvc_v4l2_do_ioctl * Uvc_video.c (drivers\media\video\uvc)** 函数功能:该函数的目的是表征这是一个摄像头设备*/
static int myuvc_vidioc_querycap(struct file *file, void  *priv,struct v4l2_capability *cap)
{    memset(cap, 0, sizeof *cap);strcpy(cap->driver, "myuvc");strcpy(cap->card, "myuvc");cap->version = 1;/* V4L2_CAP_VIDEO_CAPTURE表示这是一个摄像头设备，V4L2_CAP_STREAMING表明可以通过* qbuf或者dbuf来获得数据，V4L2_CAP_READWRITE表示可以通过读写函数来获取数据，因此* 这个摄像头驱动支持两种获取数据的格式*/cap->capabilities = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;return 0;
}/* A3 列举支持哪种格式* 参考: uvc_fmts 数组*/
static int myuvc_vidioc_enum_fmt_vid_cap(struct file *file, void  *priv,struct v4l2_fmtdesc *f)
{/* 人工查看描述符可知我们用的摄像头只支持1种格式 */if (f->index >= 1)return -EINVAL;/* 支持什么格式呢?* 查看VideoStreaming Interface的描述符可知为VS_FORMAT_UNCOMPRESSED格式,* 得到GUID为"59 55 59 32 00 00 10 00 80 00 00 aa 00 38 9b 71"* 通过uvc_driver.c中的uvc_format_by_guid函数中的uvc_fmts对比可知，这个uvc的GUID* 与UVC_GUID_FORMAT_YUY2是一模一样的，因此这个格式为V4L2_PIX_FMT_YUYV*/strcpy(f->description, "4:2:2, packed, YUYV");f->pixelformat = V4L2_PIX_FMT_YUYV;    return 0;
}/* A4 返回当前所使用的格式 */
static int myuvc_vidioc_g_fmt_vid_cap(struct file *file, void *priv,struct v4l2_format *f)
{/* 直接从全局变量中拷贝 */memcpy(f, &myuvc_format, sizeof(myuvc_format));return (0);
}/* A5 测试驱动程序是否支持某种格式, 强制设置该格式 * 参考: uvc_v4l2_try_format*       myvivi_vidioc_try_fmt_vid_cap*/
static int myuvc_vidioc_try_fmt_vid_cap(struct file *file, void *priv,struct v4l2_format *f)
{/* 参考uvc_driver.c中的uvc_parse_streaming，里面就有V4L2_BUF_TYPE_VIDEO_CAPTURE */if (f->type != V4L2_BUF_TYPE_VIDEO_CAPTURE){return -EINVAL;}if (f->fmt.pix.pixelformat != V4L2_PIX_FMT_YUYV)return -EINVAL;/* 调整format的width, height, * 计算bytesperline, sizeimage*//* 人工查看描述符, 确定支持哪几种分辨率 * 这种方式是强制的把分辨率定死了*/f->fmt.pix.width  = frames[frame_idx].width;f->fmt.pix.height = frames[frame_idx].height;f->fmt.pix.bytesperline =(f->fmt.pix.width * bBitsPerPixel) >> 3;f->fmt.pix.sizeimage =f->fmt.pix.height * f->fmt.pix.bytesperline;return 0;
}/* A6 参考 myvivi_vidioc_s_fmt_vid_cap */
static int myuvc_vidioc_s_fmt_vid_cap(struct file *file, void *priv,struct v4l2_format *f)
{/* 该函数强制设置分辨率格式  */int ret = myuvc_vidioc_try_fmt_vid_cap(file, NULL, f);if (ret < 0)return ret;memcpy(&myuvc_format, f, sizeof(myuvc_format));return 0;
}static int myuvc_free_buffers(void)
{if (myuvc_queue.mem){vfree(myuvc_queue.mem);memset(&myuvc_queue, 0, sizeof(myuvc_queue));myuvc_queue.mem = NULL;}return 0;
}/* A7 APP调用该ioctl让驱动程序分配若干个缓存, APP将从这些缓存中读到视频数据 * 参考: uvc_alloc_buffers   在Uvc_queue.c (drivers\media\video\uvc)   */
static int myuvc_vidioc_reqbufs(struct file *file, void *priv,struct v4l2_requestbuffers *p)
{/* 申请多少个缓存 */int nbuffers = p->count;/* 每个缓存的大小 * myuvc_format.fmt.pix.sizeimage表示当前格式一屏数据的大小* PAGE_ALIGN函数是页对齐，也就是一整页一整页的来分配*/int bufsize  = PAGE_ALIGN(myuvc_format.fmt.pix.sizeimage);unsigned int i;void *mem = NULL;int ret;/* 如果之前已经分配过缓存了，那么就先释放掉 */if ((ret = myuvc_free_buffers()) < 0)goto done;/* Bail out if no buffers should be allocated. */if (nbuffers == 0)goto done;/* Decrement the number of buffers until allocation succeeds. */for (; nbuffers > 0; --nbuffers) {mem = vmalloc_32(nbuffers * bufsize);if (mem != NULL)break;}if (mem == NULL) {ret = -ENOMEM;goto done;}/* 这些缓存是一次性作为一个整体来分配的 */memset(&myuvc_queue, 0, sizeof(myuvc_queue));INIT_LIST_HEAD(&myuvc_queue.mainqueue);INIT_LIST_HEAD(&myuvc_queue.irqqueue);for (i = 0; i < nbuffers; ++i) {myuvc_queue.buffer[i].buf.index = i;myuvc_queue.buffer[i].buf.m.offset = i * bufsize;/* 缓存的大小是实际的大小，并不是页对齐之后的大小 */myuvc_queue.buffer[i].buf.length = myuvc_format.fmt.pix.sizeimage;/* type是enum v4l2_buf_type类型的，只有V4L2_BUF_TYPE_VIDEO_CAPTURE符合 */myuvc_queue.buffer[i].buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;myuvc_queue.buffer[i].buf.sequence = 0;myuvc_queue.buffer[i].buf.field = V4L2_FIELD_NONE;myuvc_queue.buffer[i].buf.memory = V4L2_MEMORY_MMAP;myuvc_queue.buffer[i].buf.flags = 0;myuvc_queue.buffer[i].state     = VIDEOBUF_IDLE;init_waitqueue_head(&myuvc_queue.buffer[i].wait);}myuvc_queue.mem = mem;myuvc_queue.count = nbuffers;myuvc_queue.buf_size = bufsize;ret = nbuffers;done:return ret;
}/* A8 查询缓存状态, 比如地址信息(APP可以用mmap进行映射) * 参考 uvc_query_buffer*/
static int myuvc_vidioc_querybuf(struct file *file, void *priv, struct v4l2_buffer *v4l2_buf)
{int ret = 0;if (v4l2_buf->index >= myuvc_queue.count) {ret = -EINVAL;goto done;}memcpy(v4l2_buf, &myuvc_queue.buffer[v4l2_buf->index].buf, sizeof(*v4l2_buf));/* 更新flags *//* 如果已经被mmap过 */if (myuvc_queue.buffer[v4l2_buf->index].vma_use_count)v4l2_buf->flags |= V4L2_BUF_FLAG_MAPPED;switch (myuvc_queue.buffer[v4l2_buf->index].state) {case VIDEOBUF_ERROR:case VIDEOBUF_DONE:v4l2_buf->flags |= V4L2_BUF_FLAG_DONE;break;case VIDEOBUF_QUEUED://放入了队列case VIDEOBUF_ACTIVE://正在队列中进行处理v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;    //还在队列中break;case VIDEOBUF_IDLE:default:break;}done:    return ret;
}/* A10 把缓冲区放入队列, 底层的硬件操作函数将会把数据放入这个队列的缓存 * 参考: uvc_queue_buffer*/
static int myuvc_vidioc_qbuf(struct file *file, void *priv, struct v4l2_buffer *v4l2_buf)
{struct myuvc_buffer *buf;/* 0. APP传入的v4l2_buf可能有问题, 要做判断 */if (v4l2_buf->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||v4l2_buf->memory != V4L2_MEMORY_MMAP) {return -EINVAL;}if (v4l2_buf->index >= myuvc_queue.count) {return -EINVAL;}buf = &myuvc_queue.buffer[v4l2_buf->index];if (buf->state != VIDEOBUF_IDLE) {return -EINVAL;}/* 1. 修改状态 */buf->state = VIDEOBUF_QUEUED;/* 刚把缓存放入队列中，这个缓存中被使用的字节数为0 */buf->buf.bytesused = 0;/* 2. 放入2个队列 *//* 队列1: 供APP使用 * 当缓冲区没有数据时,放入mainqueue队列* 当缓冲区有数据时, APP从mainqueue队列中取出*/list_add_tail(&buf->stream, &myuvc_queue.mainqueue);/* 队列2: 供产生数据的函数使用* 当采集到数据时,从irqqueue队列中取出第1个缓冲区,存入数据*/list_add_tail(&buf->irq, &myuvc_queue.irqqueue);return 0;
}/* 打印从usb设备哪里使用usb_control_msg函数获得的参数 */
static void myuvc_print_streaming_params(struct myuvc_streaming_control *ctrl)
{printk("video params:\n");printk("bmHint                   = %d\n", ctrl->bmHint);printk("bFormatIndex             = %d\n", ctrl->bFormatIndex);printk("bFrameIndex              = %d\n", ctrl->bFrameIndex);printk("dwFrameInterval          = %d\n", ctrl->dwFrameInterval);printk("wKeyFrameRate            = %d\n", ctrl->wKeyFrameRate);printk("wPFrameRate              = %d\n", ctrl->wPFrameRate);printk("wCompQuality             = %d\n", ctrl->wCompQuality);printk("wCompWindowSize          = %d\n", ctrl->wCompWindowSize);printk("wDelay                   = %d\n", ctrl->wDelay);printk("dwMaxVideoFrameSize      = %d\n", ctrl->dwMaxVideoFrameSize);printk("dwMaxPayloadTransferSize = %d\n", ctrl->dwMaxPayloadTransferSize);printk("dwClockFrequency         = %d\n", ctrl->dwClockFrequency);printk("bmFramingInfo            = %d\n", ctrl->bmFramingInfo);printk("bPreferedVersion         = %d\n", ctrl->bPreferedVersion);printk("bMinVersion              = %d\n", ctrl->bMinVersion);printk("bMinVersion              = %d\n", ctrl->bMinVersion);
}/* 参考: uvc_get_video_ctrl (ret = uvc_get_video_ctrl(video, probe, 1, GET_CUR)) static int uvc_get_video_ctrl(struct uvc_video_device *video,struct uvc_streaming_control *ctrl, int probe, __u8 query)*/
static int myuvc_get_streaming_params(struct myuvc_streaming_control *ctrl)
{__u8 *data;__u16 size;int ret;__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;/* 根据uvc版本知道发多少数据 */size = uvc_version >= 0x0110 ? 34 : 26;/* 分配缓存 */data = kmalloc(size, GFP_KERNEL);if (data == NULL)return -ENOMEM;/* 初始化管道,管道是通过端点的编号和类型生成的一个整型，然后通过这个整型数就可* 以直接找到由哪个端点来进行收发数据，本身这些信息在端点里也有，只不过将这些* 信息用函数合成一个整形数据来使用，比较方便而已，类似于文件描述符。直接使用* 文件描述符来通讯。我们初始化的这个管道就是从端点0来获得数据的管道。 * usb_rcvctrlpipe是用于产生接收的控制管道 (接收与发送都是相对于usb控制器来说的)*/pipe = (GET_CUR & 0x80) ? usb_rcvctrlpipe(myuvc_udev, 0): usb_sndctrlpipe(myuvc_udev, 0);/* 数据传输方向 * usb设备的传输方向都是针对usb控制器的，因为我们要从usb设备中读取数据，所以方向* 应该是从usb设备到usb控制器，所以是USB_DIR_IN*/type |= (GET_CUR & 0x80) ? USB_DIR_IN : USB_DIR_OUT;/* 参数: GET_CUR表示当前的usb参数，GET_MIN和GET_MAX分别是获得最大最小的usb参数 * 参数: VS_PROBE_CONTROL表示枚举参数，VS_COMMIT_CONTROL表示提交参数* 摄像头的参数是存放在VS接口描述符中的，* usb_control_msg是没有用到urb的在USB中简单进行发送和接收的一种机制，用于少量的数据通信* usb_control_msg函数是usb设备的最底层函数接口.该函数的功能是向usb设备发送数据包* 发起usb传输，就可以获得当前锁使用的参数，存储于data中，然后再将data中的数据* 赋给myuvc_streaming_control结构体* 函数的返回值:如果成功则返回传输的数据的个数，如果失败则返回一个负数*/ret = usb_control_msg(myuvc_udev, pipe, GET_CUR, type, VS_PROBE_CONTROL << 8,0 << 8 | myuvc_streaming_intf, data, size, 5000);//超时5秒if (ret < 0)goto done;/* 从uvc_get_video_ctrl中拷贝过来的* 将data中的数据赋给myuvc_streaming_control结构体*/ctrl->bmHint = le16_to_cpup((__le16 *)&data[0]);ctrl->bFormatIndex = data[2];ctrl->bFrameIndex = data[3];ctrl->dwFrameInterval = le32_to_cpup((__le32 *)&data[4]);ctrl->wKeyFrameRate = le16_to_cpup((__le16 *)&data[8]);ctrl->wPFrameRate = le16_to_cpup((__le16 *)&data[10]);ctrl->wCompQuality = le16_to_cpup((__le16 *)&data[12]);ctrl->wCompWindowSize = le16_to_cpup((__le16 *)&data[14]);ctrl->wDelay = le16_to_cpup((__le16 *)&data[16]);ctrl->dwMaxVideoFrameSize = get_unaligned_le32(&data[18]);ctrl->dwMaxPayloadTransferSize = get_unaligned_le32(&data[22]);if (size == 34) {ctrl->dwClockFrequency = get_unaligned_le32(&data[26]);ctrl->bmFramingInfo = data[30];ctrl->bPreferedVersion = data[31];ctrl->bMinVersion = data[32];ctrl->bMaxVersion = data[33];} else {//ctrl->dwClockFrequency = video->dev->clock_frequency;ctrl->bmFramingInfo = 0;ctrl->bPreferedVersion = 0;ctrl->bMinVersion = 0;ctrl->bMaxVersion = 0;}done:kfree(data);return (ret < 0) ? ret : 0;
}/* 参考: uvc_v4l2_try_format ∕uvc_probe_video *       uvc_set_video_ctrl(video, probe, 1)*/
static int myuvc_try_streaming_params(struct myuvc_streaming_control *ctrl)
{__u8 *data;__u16 size;int ret;__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;memset(ctrl, 0, sizeof *ctrl);/* ctrl->bmHint = 1;也就是说uvc规格书中D0=1，表示在协商过程中保持dwFrameInterval不变，* 什么是协商呢？就是说我们设置了一些参数，先发给usb摄像头，让他确认一下能不能用，* 如果不能用的话，从新修改然后在发给usb摄像头，确认能不能用，直到最后能用为止，* 我们再使用其他的命令把这些参数发给usb摄像头，他就可以接收这些参数，* 并且工作在这些新参数之下。*/ctrl->bmHint = 1;   /* dwFrameInterval *//* 我们只有一种格式 */ctrl->bFormatIndex = 1;/* 在该种格式下使用哪一种分辨率 */ctrl->bFrameIndex  = frame_idx + 1;/* 有VS_FRAME_UNCOMPRESSED描述符的最后一项可知，dwMinFrameInterval为15 16 05 00，* 就是十六进制0x051615------>333333(十进制) ,由规格书可知dwFrameInterval表示* 每帧之间的时间间隔，单位为100ns,那么如果该值为333333，每秒多少帧呢？* 1000000000 ns/ (333333*100)ns = 30       也就是每秒30帧*/ctrl->dwFrameInterval = 333333;/* 下面的代码跟myuvc_get_streaming_params函数基本是一样的 */size = uvc_version >= 0x0110 ? 34 : 26;data = kzalloc(size, GFP_KERNEL);if (data == NULL)return -ENOMEM;*(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);data[2] = ctrl->bFormatIndex;data[3] = ctrl->bFrameIndex;*(__le32 *)&data[4] = cpu_to_le32(ctrl->dwFrameInterval);*(__le16 *)&data[8] = cpu_to_le16(ctrl->wKeyFrameRate);*(__le16 *)&data[10] = cpu_to_le16(ctrl->wPFrameRate);*(__le16 *)&data[12] = cpu_to_le16(ctrl->wCompQuality);*(__le16 *)&data[14] = cpu_to_le16(ctrl->wCompWindowSize);*(__le16 *)&data[16] = cpu_to_le16(ctrl->wDelay);put_unaligned_le32(ctrl->dwMaxVideoFrameSize, &data[18]);put_unaligned_le32(ctrl->dwMaxPayloadTransferSize, &data[22]);if (size == 34) {put_unaligned_le32(ctrl->dwClockFrequency, &data[26]);data[30] = ctrl->bmFramingInfo;data[31] = ctrl->bPreferedVersion;data[32] = ctrl->bMinVersion;data[33] = ctrl->bMaxVersion;}/* SET_CUR表示设置当前参数，与usb设备进行设备信息的查询和设置时，使用端点0 */pipe = (SET_CUR & 0x80) ? usb_rcvctrlpipe(myuvc_udev, 0): usb_sndctrlpipe(myuvc_udev, 0);type |= (SET_CUR & 0x80) ? USB_DIR_IN : USB_DIR_OUT;/* 参数VS_PROBE_CONTROL只是枚举，尝试而已，并不是设置，真正要设置的话是需要使用* 参数VS_COMMIT_CONTROL，因为我们现在只是枚举这些参数是否能用，并不是真正想要设置* 这些参数，知道参数可用使用我们才真正使用VS_COMMIT_CONTROL参数来设置。*/ret = usb_control_msg(myuvc_udev, pipe, SET_CUR, type, VS_PROBE_CONTROL << 8,0 << 8 | myuvc_streaming_intf, data, size, 5000);kfree(data);return (ret < 0) ? ret : 0;}/* 参考: uvc_v4l2_try_format ∕uvc_probe_video *       uvc_set_video_ctrl(video, probe, 1)* myuvc_set_streaming_params这个函数基本和myuvc_try_streaming_params是一样的，* 只不过这个函数不需要我们在甘薯内部设置myuvc_streaming_control而已，是由参数* 传递进来的，直接使用usb_control_msg函数将参数发送出去即可*/
static int myuvc_set_streaming_params(struct myuvc_streaming_control *ctrl)
{__u8 *data;__u16 size;int ret;__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;size = uvc_version >= 0x0110 ? 34 : 26;data = kzalloc(size, GFP_KERNEL);if (data == NULL)return -ENOMEM;*(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);data[2] = ctrl->bFormatIndex;data[3] = ctrl->bFrameIndex;*(__le32 *)&data[4] = cpu_to_le32(ctrl->dwFrameInterval);*(__le16 *)&data[8] = cpu_to_le16(ctrl->wKeyFrameRate);*(__le16 *)&data[10] = cpu_to_le16(ctrl->wPFrameRate);*(__le16 *)&data[12] = cpu_to_le16(ctrl->wCompQuality);*(__le16 *)&data[14] = cpu_to_le16(ctrl->wCompWindowSize);*(__le16 *)&data[16] = cpu_to_le16(ctrl->wDelay);put_unaligned_le32(ctrl->dwMaxVideoFrameSize, &data[18]);put_unaligned_le32(ctrl->dwMaxPayloadTransferSize, &data[22]);if (size == 34) {put_unaligned_le32(ctrl->dwClockFrequency, &data[26]);data[30] = ctrl->bmFramingInfo;data[31] = ctrl->bPreferedVersion;data[32] = ctrl->bMinVersion;data[33] = ctrl->bMaxVersion;}pipe = (SET_CUR & 0x80) ? usb_rcvctrlpipe(myuvc_udev, 0): usb_sndctrlpipe(myuvc_udev, 0);type |= (SET_CUR & 0x80) ? USB_DIR_IN : USB_DIR_OUT;ret = usb_control_msg(myuvc_udev, pipe, SET_CUR, type, VS_COMMIT_CONTROL << 8,0 << 8 | myuvc_streaming_intf, data, size, 5000);kfree(data);return (ret < 0) ? ret : 0;}static void myuvc_uninit_urbs(void)
{int i;for (i = 0; i < MYUVC_URBS; ++i) {if (myuvc_queue.urb_buffer[i]){usb_buffer_free(myuvc_udev, myuvc_queue.urb_size, myuvc_queue.urb_buffer[i], myuvc_queue.urb_dma[i]);myuvc_queue.urb_buffer[i] = NULL;}if (myuvc_queue.urb[i]){usb_free_urb(myuvc_queue.urb[i]);myuvc_queue.urb[i] = NULL;}}
}/* 参考: uvc_video_complete / uvc_video_decode_isoc */
static void myuvc_video_complete(struct urb *urb)
{u8 *src;u8 *dest;int ret, i;int len;int maxlen;int nbytes;struct myuvc_buffer *buf;switch (urb->status) {case 0:break;default:printk("Non-zero status (%d) in video ""completion handler.\n", urb->status);return;}/* 从irqqueue队列中取出第1个缓冲区 */if (!list_empty(&myuvc_queue.irqqueue)){buf = list_first_entry(&myuvc_queue.irqqueue, struct myuvc_buffer, irq);/* 一次urb传输里面包含的子包数，依次取出每一个子包 */for (i = 0; i < urb->number_of_packets; ++i) {if (urb->iso_frame_desc[i].status < 0) {printk("USB isochronous frame ""lost (%d).\n", urb->iso_frame_desc[i].status);continue;}/* 数据源 */src  = urb->transfer_buffer + urb->iso_frame_desc[i].offset;/* 数据的目的地址，buf->buf.bytesused表示这个buffer目前已经存放了多少个字节的数据 * 因为urb需要经过几次传输才能填满一个buf，所以源地址等于buf的偏移还要加上这个* buf已经使用的字节数。*/dest = myuvc_queue.mem + buf->buf.m.offset + buf->buf.bytesused;/* 每一个子包的实际长度 */len = urb->iso_frame_desc[i].actual_length;/* 判断数据是否有效，参考uvc_video_decode_start，该函数的作用是对数据的* 头部进行判断*//* Sanity checks:* - packet must be at least 2 bytes long* - bHeaderLength value must be at least 2 bytes (see above)* - bHeaderLength value can't be larger than the packet size.*//* URB数据含义:* src[0] : 头部长度* src[1] : 错误状态* 由以上的分析可知，得到的每一个子包会包含一个头部，在头部之后才是有效的视频数据*/if (len < 2 || src[0] < 2 || src[0] > len)continue;/* Skip payloads marked with the error bit ("error frames"). */if (src[1] & UVC_STREAM_ERR) {printk("Dropping payload (error bit set).\n");continue;}/* 参考uvc_video_decode_data函数，该函数是对摄像头数据的拷贝 *//* 除去头部后的数据长度。真正的视频数据长度 */len -= src[0];/* 缓冲区最多还能存多少数据 */maxlen = buf->buf.length - buf->buf.bytesused;/* 最终要复制的数据长度 */nbytes = min(len, maxlen);/* 复制数据 */memcpy(dest, src + src[0], nbytes);buf->buf.bytesused += nbytes;/* 判断一帧数据是否已经全部接收到 * 参考uvc_video_decode_end函数，该函数的功能是判断一帧数据是否接收完成*/if (len > maxlen) {buf->state = VIDEOBUF_DONE;}/* Mark the buffer as done if the EOF marker is set. * 如果状态标志中有UVC_STREAM_EOF标志，并且已经收到数据，* 则说明数据已经全部收到*/if (src[1] & UVC_STREAM_EOF && buf->buf.bytesused != 0) {printk("Frame complete (EOF found).\n");if (len == 0)printk("EOF in empty payload.\n");buf->state = VIDEOBUF_DONE;}}/* 当接收完一帧数据, * 从irqqueue中删除这个缓冲区* 唤醒等待数据的进程 */if (buf->state == VIDEOBUF_DONE ||buf->state == VIDEOBUF_ERROR){list_del(&buf->irq);wake_up(&buf->wait);}}/* 再次提交URB */if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {printk("Failed to resubmit video URB (%d).\n", ret);}
}/* 参考: uvc_init_video_isoc */
static int myuvc_alloc_init_urbs(void)
{u16 psize;u32 size;/* 传输一帧数据所用的包数 */int npackets;int i;int j;struct urb *urb;/* wMaxPacketSize为1024的端点属于VS接口中的第8个bAlternateSetting的,* 是由我们自己选择的。*/psize = wMaxPacketSize; /* 实时传输端点一次能传输的最大字节数 *//* 是从usb设备中读取出来的 */size  = myuvc_params.dwMaxVideoFrameSize;  /* 一帧数据的最大长度 *//* 向上取整 */npackets = DIV_ROUND_UP(size, psize);if (npackets > 32)npackets = 32;size = myuvc_queue.urb_size = psize * npackets;/* 总共分配了5个urb，也就是每一帧数据对应一个urb */for (i = 0; i < MYUVC_URBS; ++i) {/* 1. 分配usb_buffers，最后一个参数 */myuvc_queue.urb_buffer[i] = usb_buffer_alloc(myuvc_udev, size,GFP_KERNEL | __GFP_NOWARN, &myuvc_queue.urb_dma[i]);/* 2. 分配urb */myuvc_queue.urb[i] = usb_alloc_urb(npackets, GFP_KERNEL);if (!myuvc_queue.urb_buffer[i] || !myuvc_queue.urb[i]){myuvc_uninit_urbs();return -ENOMEM;}}/* 3. 设置urb */for (i = 0; i < MYUVC_URBS; ++i) {urb = myuvc_queue.urb[i];urb->dev = myuvc_udev;urb->context = NULL;/* 在开始函数中使用usb_set_interface函数设置了VS接口中的第8个bAlternateSetting，* 该bAlternateSetting中的端点地址bEndpointAddress为0x81，由描述符可知。*/urb->pipe = usb_rcvisocpipe(myuvc_udev,myuvc_bEndpointAddress);urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;/* 在开始函数中使用usb_set_interface函数设置了VS接口中的第8个bAlternateSetting，* 该bAlternateSetting中的bInterval为1，由描述符可知。*/urb->interval = 1;urb->transfer_buffer = myuvc_queue.urb_buffer[i];/* urb的物理地址 */urb->transfer_dma = myuvc_queue.urb_dma[i];/* 当这个驱动程序收到一帧数据之后，就会产生一个中断，这就是中断处理函数 */urb->complete = myuvc_video_complete;/* 这个urb总共要传输多少次数据 */urb->number_of_packets = npackets;/* urb传输的数据总共多大 */urb->transfer_buffer_length = size;/* iso表示实时传输。* 因为每个urb都要传输npackets次才能完成一帧的数据传输，所以每次传输数据的* 偏移和大小都存放在urb->iso_frame_desc中*/for (j = 0; j < npackets; ++j) {urb->iso_frame_desc[j].offset = j * psize;urb->iso_frame_desc[j].length = psize;}}return 0;
}/* A11 启动传输 * 参考: uvc_video_enable(video, 1):*           uvc_commit_video*           uvc_init_video*/
static int myuvc_vidioc_streamon(struct file *file, void *priv, enum v4l2_buf_type i)
{int ret;/* 1. 向USB摄像头设置参数: 比如使用哪个format, 使用这个format下的哪个frame(分辨率) * 参考: uvc_set_video_ctrl / uvc_get_video_ctrl* 1.1 根据一个结构体uvc_streaming_control设置数据包: 可以手工设置,也可以读出后再修改* 1.2 调用usb_control_msg发出数据包*//* a. 测试参数 */ret = myuvc_try_streaming_params(&myuvc_params);printk("myuvc_try_streaming_params ret = %d\n", ret);/* b. 取出参数 * 经过测试发现测试函数和设置函数直接必须要有取出参数这个函数，因为当向usb设备发* 送一个参数之后，如果usb设备能够接收这个参数，他就会把这个参数保存起来，* 并且会做一些修正，比如说，我们在使用myuvc_try_streaming_params函数的时候只是发送* 了几个参数，后面的参数都没有发送。刚才发给usb设备的参数，usb设备发现他能够接收* 这些参数，他就会把后面的参数补齐，接下来我们就应该使用myuvc_get_streaming_params函数* 将补齐的参数一次性读出来。最后调用设置函数即可。*/ret = myuvc_get_streaming_params(&myuvc_params);printk("myuvc_get_streaming_params ret = %d\n", ret);/* c. 设置参数 */ret = myuvc_set_streaming_params(&myuvc_params);printk("myuvc_set_streaming_params ret = %d\n", ret);myuvc_print_streaming_params(&myuvc_params);/* 参考uvc_init_video* d. 设置VideoStreaming Interface所使用的setting* d.1 从myuvc_params确定带宽* d.2 根据setting的endpoint能传输的wMaxPacketSize*     找到能满足该带宽的setting*//* 手工确定:* bandwidth = myuvc_params.dwMaxPayloadTransferSize = 1024* 观察lsusb -v -d 0x1e4e:的结果:*                wMaxPacketSize     0x0400  1x 1024 bytes* bAlternateSetting       8* usb_set_interface函数的作用是设置usb设备使用VideoStreaming Interface中的哪个* 设置来进行传输数据。我们通过lsusb命令查看描述符，发现其每个设置描述符中都只有* 一个端点，这可能就是uvc规范，因此找到设置就可以使用唯一的端点进行传输数据。* 因为usb设备就是使用端点来进行数据传输的。*/usb_set_interface(myuvc_udev, myuvc_streaming_intf, myuvc_streaming_bAlternateSetting);/* 2. 分配设置URB */ret = myuvc_alloc_init_urbs();if (ret)printk("myuvc_alloc_init_urbs err : ret = %d\n", ret);/* 3. 提交URB以接收数据 * 因为这5个urb设置的完成函数都是同一个完成函数，相当于有5个urb包来共同从usb摄像头* 获取数据，放入myuvc_buffer中。*/for (i = 0; i < MYUVC_URBS; ++i) {if ((ret = usb_submit_urb(myuvc_queue.urb[i], GFP_KERNEL)) < 0) {printk("Failed to submit URB %u (%d).\n", i, ret);myuvc_uninit_urbs();return ret;}}return 0;
}/* A13 APP通过poll/select确定有数据后, 把缓存从队列中取出来* 参考: uvc_dequeue_buffer*/
static int myuvc_vidioc_dqbuf(struct file *file, void *priv, struct v4l2_buffer *v4l2_buf)
{/* APP发现数据就绪后, 从mainqueue里取出这个buffer */struct myuvc_buffer *buf;int ret = 0;if (list_empty(&myuvc_queue.mainqueue)) {ret = -EINVAL;goto done;}buf = list_first_entry(&myuvc_queue.mainqueue, struct myuvc_buffer, stream);switch (buf->state) {case VIDEOBUF_ERROR:ret = -EIO;case VIDEOBUF_DONE:buf->state = VIDEOBUF_IDLE;break;case VIDEOBUF_IDLE:case VIDEOBUF_QUEUED:case VIDEOBUF_ACTIVE:default:ret = -EINVAL;goto done;}list_del(&buf->stream);done:return ret;
}/** A14 之前已经通过mmap映射了缓存, APP可以直接读数据* A15 再次调用myuvc_vidioc_qbuf把缓存放入队列* A16 poll...*//* A17 停止 * 参考 : uvc_video_enable(video, 0)*/
static int myuvc_vidioc_streamoff(struct file *file, void *priv, enum v4l2_buf_type t)
{struct urb *urb;unsigned int i;/* 1. kill URB */for (i = 0; i < MYUVC_URBS; ++i) {if ((urb = myuvc_queue.urb[i]) == NULL)continue;usb_kill_urb(urb);}/* 2. free URB */myuvc_uninit_urbs();/* 3. 设置VideoStreaming Interface为setting 0 ，即为初始状态* 让这个VS接口的处于不工作状态，可以从uvc规范里面找到这么做的原因*/usb_set_interface(myuvc_udev, myuvc_streaming_intf, 0);return 0;
}/* Control handling *//* Extract the bit string specified by mapping->offset and mapping->size* from the little-endian data stored at 'data' and return the result as* a signed 32bit integer. Sign extension will be performed if the mapping* references a signed data type.* 该函数从uvc驱动里面拷贝过来的，函数的功能是从如下的信息中计算出所需的值//以下结构体用于参考{.id     = V4L2_CID_BRIGHTNESS,.name       = "Brightness",.entity     = UVC_GUID_UVC_PROCESSING,.selector   = PU_BRIGHTNESS_CONTROL,.size       = 16,.offset     = 0,.v4l2_type  = V4L2_CTRL_TYPE_INTEGER,.data_type  = UVC_CTRL_DATA_TYPE_SIGNED,},*/
static __s32 myuvc_get_le_value(const __u8 *data)
{int bits = 16;  //sizeint offset = 0;     //offset__s32 value = 0;__u8 mask;data += offset / 8;offset &= 7;mask = ((1LL << bits) - 1) << offset;for (; bits > 0; data++) {__u8 byte = *data & mask;value |= offset > 0 ? (byte >> offset) : (byte << (-offset));bits -= 8 - (offset > 0 ? offset : 0);offset -= 8;mask = (1 << bits) - 1;}/* Sign-extend the value if needed. */value |= -(value & (1 << (16 - 1)));return value;
}/* Set the bit string specified by mapping->offset and mapping->size* in the little-endian data stored at 'data' to the value 'value'.* 该函数的功能:将一个数转换为一个16位的，用于向usb设备发起设置属性的请求，* 由uvc_control_mapping结构体可知，设置亮度需要16位，因此需要将一个整数转化为16位*/
static void myuvc_set_le_value(__s32 value, __u8 *data)
{int bits = 16;int offset = 0;__u8 mask;data += offset / 8;offset &= 7;for (; bits > 0; data++) {mask = ((1LL << bits) - 1) << offset;*data = (*data & ~mask) | ((value << offset) & mask);value >>= offset ? offset : 8;bits -= 8 - offset;offset = 0;}
}/* 参考:uvc_query_v4l2_ctrl * 对属性的操作，这个驱动程序只支持亮度的操作*/
int myuvc_vidioc_queryctrl (struct file *file, void *fh,struct v4l2_queryctrl *ctrl)
{__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;int ret;u8 data[2];/* V4L2_CID_BRIGHTNESS宏是从uvc_control_mapping结构体数组中的index拷贝的 */if (ctrl->id != V4L2_CID_BRIGHTNESS)return -EINVAL;memset(ctrl, 0, sizeof *ctrl);ctrl->id   = V4L2_CID_BRIGHTNESS;ctrl->type = V4L2_CTRL_TYPE_INTEGER;strcpy(ctrl->name, "MyUVC_BRIGHTNESS");ctrl->flags = 0;/* 接收数据，由端点0发起控制传输 */pipe = usb_rcvctrlpipe(myuvc_udev, 0);type |= USB_DIR_IN;/*  参考的详细属性信息   {.id     = V4L2_CID_BRIGHTNESS,.name       = "Brightness",.entity     = UVC_GUID_UVC_PROCESSING,.selector   = PU_BRIGHTNESS_CONTROL,.size       = 16,.offset     = 0,.v4l2_type  = V4L2_CTRL_TYPE_INTEGER,.data_type  = UVC_CTRL_DATA_TYPE_SIGNED,},*//* 发起USB传输确定这些值，得到两个字节的数据 * 参数ProcessingUnitID表示PU号，在自己打印的VC的额外
描述符中可以找到，* 参数2表示发送的数据大小，由uvc_ctrls数组中的信息可知。* 参数PU_BRIGHTNESS_CONTROL表示PU中的哪个属性*/ret = usb_control_msg(myuvc_udev, pipe, GET_MIN, type, PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;/* 根据获得数据取出在最小值 * 由uvc规范可知，从usb设备获取的最小值(GET_MIN)是16位的数据，因此需要将这16位的数* 转换为一个整数*/ctrl->minimum = myuvc_get_le_value(data);   /* Note signedness */ret = usb_control_msg(myuvc_udev, pipe, GET_MAX, type,  PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;ctrl->maximum = myuvc_get_le_value(data);   /* Note signedness *//* 获得阶梯值，所谓阶梯值表示当调整亮度时，每一小格的亮度最小值是多少。 */ret = usb_control_msg(myuvc_udev, pipe, GET_RES, type, PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;ctrl->step = myuvc_get_le_value(data);  /* Note signedness */ret = usb_control_msg(myuvc_udev, pipe, GET_DEF, type, PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;ctrl->default_value = myuvc_get_le_value(data); /* Note signedness */printk("Brightness: min =%d, max = %d, step = %d, default = %d\n", ctrl->minimum, ctrl->maximum, ctrl->step, ctrl->default_value);return 0;
}/* 参考 : uvc_ctrl_get * 函数功能是获取当前的是属性值，*/
int myuvc_vidioc_g_ctrl (struct file *file, void *fh,struct v4l2_control *ctrl)
{__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;int ret;u8 data[2];if (ctrl->id != V4L2_CID_BRIGHTNESS)return -EINVAL;pipe = usb_rcvctrlpipe(myuvc_udev, 0);type |= USB_DIR_IN;/* 查询myuvc_udev设备中的myuvc_control_intf接口中的ProcessingUnitID中的当前(GET_CUR)* 亮度值(PU_BRIGHTNESS_CONTROL) */ret = usb_control_msg(myuvc_udev, pipe, GET_CUR, type, PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;ctrl->value = myuvc_get_le_value(data); /* Note signedness */return 0;
}/* 参考: uvc_ctrl_set/uvc_ctrl_commit */
int myuvc_vidioc_s_ctrl (struct file *file, void *fh,struct v4l2_control *ctrl)
{__u8 type = USB_TYPE_CLASS | USB_RECIP_INTERFACE;unsigned int pipe;int ret;u8 data[2];if (ctrl->id != V4L2_CID_BRIGHTNESS)return -EINVAL;myuvc_set_le_value(ctrl->value, data);pipe = usb_sndctrlpipe(myuvc_udev, 0);type |= USB_DIR_OUT;ret = usb_control_msg(myuvc_udev, pipe, SET_CUR, type, PU_BRIGHTNESS_CONTROL << 8,ProcessingUnitID  << 8 | myuvc_control_intf, data, 2, 5000);if (ret != 2)return -EIO;return 0;
}static const struct v4l2_ioctl_ops myuvc_ioctl_ops = {// 表示它是一个摄像头设备.vidioc_querycap      = myuvc_vidioc_querycap,/* 用于列举、获得、测试、设置摄像头的数据的格式 */.vidioc_enum_fmt_vid_cap  = myuvc_vidioc_enum_fmt_vid_cap,.vidioc_g_fmt_vid_cap     = myuvc_vidioc_g_fmt_vid_cap,.vidioc_try_fmt_vid_cap   = myuvc_vidioc_try_fmt_vid_cap,.vidioc_s_fmt_vid_cap     = myuvc_vidioc_s_fmt_vid_cap,/* 缓冲区操作: 申请/查询/放入队列/取出队列 */.vidioc_reqbufs       = myuvc_vidioc_reqbufs,.vidioc_querybuf      = myuvc_vidioc_querybuf,.vidioc_qbuf          = myuvc_vidioc_qbuf,.vidioc_dqbuf         = myuvc_vidioc_dqbuf,/* 查询/获得/设置属性 */.vidioc_queryctrl     = myuvc_vidioc_queryctrl,.vidioc_g_ctrl        = myuvc_vidioc_g_ctrl,.vidioc_s_ctrl        = myuvc_vidioc_s_ctrl,// 启动/停止.vidioc_streamon      = myuvc_vidioc_streamon,.vidioc_streamoff     = myuvc_vidioc_streamoff,
};/* A1 */
static int myuvc_open(struct file *file)
{return 0;
}static void myuvc_vm_open(struct vm_area_struct *vma)
{struct myuvc_buffer *buffer = vma->vm_private_data;/* buffer的引用计数加1 */buffer->vma_use_count++;
}static void myuvc_vm_close(struct vm_area_struct *vma)
{struct myuvc_buffer *buffer = vma->vm_private_data;buffer->vma_use_count--;
}static struct vm_operations_struct myuvc_vm_ops = {.open       = myuvc_vm_open,.close      = myuvc_vm_close,
};/* A9 把缓存映射到APP的空间,以后APP就可以直接操作这块缓存 * 参考: uvc_v4l2_mmap* mmap函数在应用层传进来的参数经过VFS后，参数会被封装为一个vm_area_struct结构体*/
static int myuvc_mmap(struct file *file, struct vm_area_struct *vma)
{struct myuvc_buffer *buffer;struct page *page;unsigned long addr, start, size;unsigned int i;int ret = 0;start = vma->vm_start;size = vma->vm_end - vma->vm_start;/* 应用程序调用mmap函数时, 会传入offset参数* 根据这个offset找出指定的缓冲区buffer*/for (i = 0; i < myuvc_queue.count; ++i) {buffer = &myuvc_queue.buffer[i];if ((buffer->buf.m.offset >> PAGE_SHIFT) == vma->vm_pgoff)break;}if (i == myuvc_queue.count || size != myuvc_queue.buf_size) {ret = -EINVAL;goto done;}/** VM_IO marks the area as being an mmaped region for I/O to a* device. It also prevents the region from being core dumped.*/vma->vm_flags |= VM_IO;/* 根据虚拟地址找到缓冲区对应的page构体 */addr = (unsigned long)myuvc_queue.mem + buffer->buf.m.offset;while (size > 0) {/* 将vmalloc分配的内存转化为页 */page = vmalloc_to_page((void *)addr);/* 把page和APP传入的虚拟地址挂构 */if ((ret = vm_insert_page(vma, start, page)) < 0)goto done;start += PAGE_SIZE;addr += PAGE_SIZE;size -= PAGE_SIZE;}vma->vm_ops = &myuvc_vm_ops;vma->vm_private_data = buffer;myuvc_vm_open(vma);done:return ret;
}/* A12 APP调用POLL/select来确定缓存是否就绪(有数据) * 参考 : uvc_v4l2_poll*/
static unsigned int myuvc_poll(struct file *file, struct poll_table_struct *wait)
{struct myuvc_buffer *buf;unsigned int mask = 0;/* 从mainqueuq中取出第1个缓冲区 *//*判断它的状态, 如果未就绪, 休眠 */if (list_empty(&myuvc_queue.mainqueue)) {mask |= POLLERR;goto done;}buf = list_first_entry(&myuvc_queue.mainqueue, struct myuvc_buffer, stream);poll_wait(file, &buf->wait, wait);if (buf->state == VIDEOBUF_DONE ||buf->state == VIDEOBUF_ERROR)mask |= POLLIN | POLLRDNORM;done:return mask;
}/* A18 关闭 */
static int myuvc_close(struct file *file)
{return 0;
}static const struct v4l2_file_operations myuvc_fops = {.owner      = THIS_MODULE,.open       = myuvc_open,.release    = myuvc_close,.mmap       = myuvc_mmap,/* 最终会调用myuvc_vdev->ioctl_ops中的ioctl函数 */.ioctl      = video_ioctl2, /* V4L2 ioctl handler */.poll       = myuvc_poll,
};static void myuvc_release(struct video_device *vdev)
{
}static int myuvc_probe(struct usb_interface *intf,const struct usb_device_id *id)
{static int cnt = 0;struct usb_device *dev = interface_to_usbdev(intf);myuvc_udev = dev;printk("myuvc_probe : cnt = %d\n", cnt++);/* 参考uvc_driver.c * 这是为了获得当前接口描述符的编号*/if (cnt == 1){/* 获得当前VC接口描述符的编号 */myuvc_control_intf = intf->cur_altsetting->desc.bInterfaceNumber;}else if (cnt == 2){   /* 获得当前VS接口描述符的编号 */myuvc_streaming_intf = intf->cur_altsetting->desc.bInterfaceNumber;}/* usb匹配成功后会执行两次probe函数，因为usb_device_id中有两个接口 */if (cnt == 2){/* 1. 分配一个video_device结构体 */myuvc_vdev = video_device_alloc();/* 2. 设置 *//* 2.1 */myuvc_vdev->release = myuvc_release;/* 2.2 */myuvc_vdev->fops    = &myuvc_fops;/* 2.3 */myuvc_vdev->ioctl_ops = &myuvc_ioctl_ops;/* 3. 注册 ,以下信息是通过追踪源代码得到的结论* 参数-1表示分配第一个可用的号* which device node number (0 == /dev/video0, 1 == /dev/video1, ...*            -1 == first free) */video_register_device(myuvc_vdev, VFL_TYPE_GRABBER, -1);//参考vivi.c}return 0;
}static void myuvc_disconnect(struct usb_interface *intf)
{static int cnt = 0;printk("myuvc_disconnect : cnt = %d\n", cnt++);if (cnt == 2){video_unregister_device(myuvc_vdev);video_device_release(myuvc_vdev);}}/* 这些设备是逻辑上的设备，对应的术语叫做INTERFACE，一般usb摄像头有两个INTERFACE，一个是* 控制接口，一个是流接口。*/
static struct usb_device_id myuvc_ids[] = {/* Generic USB Video Class */{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) },  /* VideoControl Interface */{ USB_INTERFACE_INFO(USB_CLASS_VIDEO, 2, 0) },  /* VideoStreaming Interface */{}
};/* 1. 分配usb_driver */
/* 2. 设置 */
static struct usb_driver myuvc_driver = {.name       = "myuvc",.probe      = myuvc_probe,.disconnect = myuvc_disconnect,.id_table   = myuvc_ids,
};static int myuvc_init(void)
{/* 3. 注册 */usb_register(&myuvc_driver);return 0;
}static void myuvc_exit(void)
{usb_deregister(&myuvc_driver);
}module_init(myuvc_init);
module_exit(myuvc_exit);MODULE_LICENSE("GPL");