2.4 自己编写一个vivi驱动程序

学习目标：从零编写一个vivi驱动程序，并测试；

一. vivi驱动应用程序调用过程

上节对xawtv对vivi程序调用欧城进行了详细分析，可总结为以下流程：

二、仿照vivi.c编写myvivi.c驱动程序

 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/ioport.h>
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/pci.h>
 #include <linux/random.h>
 #include <linux/version.h>
 #include <linux/mutex.h>
 #include <linux/videodev2.h>
 #include <linux/dma-mapping.h>
 #include <linux/interrupt.h>
 #include <linux/kthread.h>
 #include <linux/highmem.h>
 #include <linux/freezer.h>
 #include <media/videobuf-vmalloc.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-ioctl.h>

 static struct v4l2_format myvivi_format;

 /* 队列操作1: 定义 */
 static struct videobuf_queue myvivi_vb_vidqueue;
 static spinlock_t myvivi_queue_slock;

 static struct list_head myvivi_vb_local_queue; //定义本地队列，用于把videobuf放入该队列的尾部

 static struct timer_list myvivi_timer; //定义定时器

 /* ------------------------------------------------------------------
     Videobuf operations
    ------------------------------------------------------------------*/
 /* APP调用ioctl VIDIOC_REQBUFS时会导致此函数被调用,
  * 它重新调整count和size
  */
 static int myvivi_buffer_setup(struct videobuf_queue *vq, unsigned int *count, unsigned int *size)
 {

     *size = myvivi_format.fmt.pix.sizeimage;

     if ( == *count)
         *count = ;

     return ;
 }

 /* APP调用ioctlVIDIOC_QBUF时导致此函数被调用,
  * 它会填充video_buffer结构体并调用videobuf_iolock来分配内存
  *
  */
 static int myvivi_buffer_prepare(struct videobuf_queue *vq, struct videobuf_buffer *vb,
                         enum v4l2_field field)
 {
     /* 0. 设置videobuf */
     vb->size = myvivi_format.fmt.pix.sizeimage;
     vb->bytesperline = myvivi_format.fmt.pix.bytesperline;
     vb->width  = myvivi_format.fmt.pix.width;
     vb->height = myvivi_format.fmt.pix.height;
     vb->field  = field;

     /* 1. 做些准备工作 */

 #if 0
     /* 2. 调用videobuf_iolock为类型为V4L2_MEMORY_USERPTR的videobuf分配内存 */
     if (VIDEOBUF_NEEDS_INIT == buf->vb.state) {
         rc = videobuf_iolock(vq, &buf->vb, NULL);
         if (rc < )
             goto fail;
     }
 #endif
     /* 3. 设置状态 */
     vb->state = VIDEOBUF_PREPARED;

     return ;
 }

 /* APP调用ioctl VIDIOC_QBUF时:
  * 1. 先调用buf_prepare进行一些准备工作
  * 2. 把buf放入stream队列
  * 3. 调用buf_queue(起通知、记录作用)
  */
 static void myvivi_buffer_queue(struct videobuf_queue *vq, struct videobuf_buffer *vb)
 {
     vb->state = VIDEOBUF_QUEUED;

     /* 把videobuf放入本地一个队列尾部
      * 定时器处理函数就可以从本地队列取出videobuf
      */
     list_add_tail(&vb->queue, &myvivi_vb_local_queue);
 }

 /* APP不再使用队列时, 用它来释放内存 */
 static void myvivi_buffer_release(struct videobuf_queue *vq,
                struct videobuf_buffer *vb)
 {
     videobuf_vmalloc_free(vb);
     vb->state = VIDEOBUF_NEEDS_INIT;
 }

 static struct videobuf_queue_ops myvivi_video_qops = {
     .buf_setup      = myvivi_buffer_setup, /* 计算大小以免浪费 */
     .buf_prepare    = myvivi_buffer_prepare,
     .buf_queue      = myvivi_buffer_queue,
     .buf_release    = myvivi_buffer_release,
 };

 /* ------------------------------------------------------------------
     File operations for the device
    ------------------------------------------------------------------*/

 static int myvivi_open(struct file *file)
 {
     /* 队列操作2: 初始化 */
     videobuf_queue_vmalloc_init(&myvivi_vb_vidqueue, &myvivi_video_qops,
             NULL, &myvivi_queue_slock, V4L2_BUF_TYPE_VIDEO_CAPTURE, V4L2_FIELD_INTERLACED,
             sizeof(struct videobuf_buffer), NULL); /* 倒数第2个参数是buffer的头部大小 */

     myvivi_timer.expires = jiffies + ;
     add_timer(&myvivi_timer);

     return ;
 }

 static int myvivi_close(struct file *file)
 {
     del_timer(&myvivi_timer);
     videobuf_stop(&myvivi_vb_vidqueue);
     videobuf_mmap_free(&myvivi_vb_vidqueue);

     return ;
 }

 static int myvivi_mmap(struct file *file, struct vm_area_struct *vma)
 {
     return videobuf_mmap_mapper(&myvivi_vb_vidqueue, vma);
 }

 static unsigned int myvivi_poll(struct file *file, struct poll_table_struct *wait)
 {
     return videobuf_poll_stream(file, &myvivi_vb_vidqueue, wait);
 }

 static int myvivi_vidioc_querycap(struct file *file, void  *priv,
                     struct v4l2_capability *cap)
 {
     strcpy(cap->driver, "myvivi");
     strcpy(cap->card, "myvivi");
     cap->version = 0x0001;
     cap->capabilities =    V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
     return ;
 }

 /* 列举支持哪种格式 */
 static int myvivi_vidioc_enum_fmt_vid_cap(struct file *file, void  *priv,
                     struct v4l2_fmtdesc *f)
 {
     if (f->index >= )
         return -EINVAL;

     strcpy(f->description, "4:2:2, packed, YUYV");
     f->pixelformat = V4L2_PIX_FMT_YUYV;
     return ;
 }

 /* 返回当前所使用的格式 */
 static int myvivi_vidioc_g_fmt_vid_cap(struct file *file, void *priv,
                     struct v4l2_format *f)
 {
     memcpy(f, &myvivi_format, sizeof(myvivi_format));
     return ();
 }

 /* 测试驱动程序是否支持某种格式 */
 static int myvivi_vidioc_try_fmt_vid_cap(struct file *file, void *priv,
             struct v4l2_format *f)
 {
     unsigned int maxw, maxh;
     enum v4l2_field field;

     if (f->fmt.pix.pixelformat != V4L2_PIX_FMT_YUYV)
         return -EINVAL;

     field = f->fmt.pix.field;

     if (field == V4L2_FIELD_ANY) {
         field = V4L2_FIELD_INTERLACED;
     } else if (V4L2_FIELD_INTERLACED != field) {
         return -EINVAL;
     }

     maxw  = ;
     maxh  = ;

     /* 调整format的width, height,
      * 计算bytesperline, sizeimage
      */
     v4l_bound_align_image(&f->fmt.pix.width, , maxw, ,
                   &f->fmt.pix.height, , maxh, , );
     f->fmt.pix.bytesperline =
         (f->fmt.pix.width * ) >> ;
     f->fmt.pix.sizeimage =
         f->fmt.pix.height * f->fmt.pix.bytesperline;

     return ;
 }

 static int myvivi_vidioc_s_fmt_vid_cap(struct file *file, void *priv,
                     struct v4l2_format *f)
 {
     int ret = myvivi_vidioc_try_fmt_vid_cap(file, NULL, f);
     if (ret < )
         return ret;

     memcpy(&myvivi_format, f, sizeof(myvivi_format));

     return ret;
 }

 static int myvivi_vidioc_reqbufs(struct file *file, void *priv,
               struct v4l2_requestbuffers *p)
 {
     return (videobuf_reqbufs(&myvivi_vb_vidqueue, p));
 }

 static int myvivi_vidioc_querybuf(struct file *file, void *priv, struct v4l2_buffer *p)
 {
     return (videobuf_querybuf(&myvivi_vb_vidqueue, p));
 }

 static int myvivi_vidioc_qbuf(struct file *file, void *priv, struct v4l2_buffer *p)
 {
     return (videobuf_qbuf(&myvivi_vb_vidqueue, p));
 }

 static int myvivi_vidioc_dqbuf(struct file *file, void *priv, struct v4l2_buffer *p)
 {
     return (videobuf_dqbuf(&myvivi_vb_vidqueue, p,
                 file->f_flags & O_NONBLOCK));
 }

 static int myvivi_vidioc_streamon(struct file *file, void *priv, enum v4l2_buf_type i)
 {
     return videobuf_streamon(&myvivi_vb_vidqueue);
 }

 static int myvivi_vidioc_streamoff(struct file *file, void *priv, enum v4l2_buf_type i)
 {
     videobuf_streamoff(&myvivi_vb_vidqueue);
     return ;
 }

 static const struct v4l2_ioctl_ops myvivi_ioctl_ops = {
         // 表示它是一个摄像头设备
         .vidioc_querycap      = myvivi_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  = myvivi_vidioc_enum_fmt_vid_cap,
         .vidioc_g_fmt_vid_cap     = myvivi_vidioc_g_fmt_vid_cap,
         .vidioc_try_fmt_vid_cap   = myvivi_vidioc_try_fmt_vid_cap,
         .vidioc_s_fmt_vid_cap     = myvivi_vidioc_s_fmt_vid_cap,

         /* 缓冲区操作: 申请/查询/放入队列/取出队列 */
         .vidioc_reqbufs       = myvivi_vidioc_reqbufs,
         .vidioc_querybuf      = myvivi_vidioc_querybuf,
         .vidioc_qbuf          = myvivi_vidioc_qbuf,
         .vidioc_dqbuf         = myvivi_vidioc_dqbuf,

         // 启动/停止
         .vidioc_streamon      = myvivi_vidioc_streamon,
         .vidioc_streamoff     = myvivi_vidioc_streamoff,
 };

 static const struct v4l2_file_operations myvivi_fops = {
     .owner        = THIS_MODULE,
     .open       = myvivi_open,
     .release    = myvivi_close,
     .mmap       = myvivi_mmap,
     .ioctl      = video_ioctl2, /* V4L2 ioctl handler */
     .poll       = myvivi_poll,
 };

 static struct video_device *myvivi_device;

 static void myvivi_release(struct video_device *vdev)
 {
 }

 static void myvivi_timer_function(unsigned long data)
 {
     struct videobuf_buffer *vb;
     void *vbuf;
     struct timeval ts;

     /* 1. 构造数据: 从队列头部取出第1个videobuf, 填充数据
      */

     /* 1.1 从本地队列取出第1个videobuf */
     if (list_empty(&myvivi_vb_local_queue)) { //已在myvivi_buffer_queue函数中放入的
         goto out;
     }

     vb = list_entry(myvivi_vb_local_queue.next,
              struct videobuf_buffer, queue);

     /* Nobody is waiting on this buffer, return */
     if (!waitqueue_active(&vb->done))
         goto out;

     /* 1.2 填充数据 */
     vbuf = videobuf_to_vmalloc(vb);
     memset(vbuf, , vb->size); // 写入0；
     vb->field_count++;
     do_gettimeofday(&ts);
     vb->ts = ts;
     vb->state = VIDEOBUF_DONE;

     /* 1.3 把videobuf从本地队列中删除 *****注意：这不是myvivi_vb_local_queue队列*/
     list_del(&vb->queue);

     /* 2. 唤醒进程: 唤醒videobuf->done上的进程 */
     wake_up(&vb->done);

 out:
     /* 3. 修改timer的超时时间 : 30fps, 1秒里有30帧数据
      *    每1/30 秒产生一帧数据
      */
     mod_timer(&myvivi_timer, jiffies + HZ/);
 }

 static int myvivi_init(void)
 {
     int error;

     /* 1. 分配一个video_device结构体 */
     myvivi_device = video_device_alloc();

     /* 2. 设置 */

     /* 2.1 */
     myvivi_device->release = myvivi_release;

     /* 2.2 */
     myvivi_device->fops    = &myvivi_fops;

     /* 2.3 */
     myvivi_device->ioctl_ops = &myvivi_ioctl_ops;

     /* 2.4 队列操作
      *  a. 定义/初始化一个队列(会用到一个spinlock)
      */
     spin_lock_init(&myvivi_queue_slock);

     /* 3. 注册 */
     error = video_register_device(myvivi_device, VFL_TYPE_GRABBER, -);

     /* 用定时器产生数据并唤醒进程 */
     init_timer(&myvivi_timer);
     myvivi_timer.function  = myvivi_timer_function;

     INIT_LIST_HEAD(&myvivi_vb_local_queue);

     return error;
 }

 static void myvivi_exit(void)
 {
     video_unregister_device(myvivi_device);
     video_device_release(myvivi_device);
 }

 module_init(myvivi_init);
 module_exit(myvivi_exit);
 MODULE_LICENSE("GPL");

（参考：https://home.cnblogs.com/u/linhaostudy和百问网）