一、vivi虚拟摄像头驱动
基于V4L2(video for linux 2)摄像头驱动程序,我们减去不需要的ioctl_fops的函数,只增加ioctl函数增加的必要的摄像头流查询等函数;
1 #include <linux/module.h> 2 #include <linux/module.h> 3 #include <linux/delay.h> 4 #include <linux/errno.h> 5 #include <linux/fs.h> 6 #include <linux/kernel.h> 7 #include <linux/slab.h> 8 #include <linux/mm.h> 9 #include <linux/ioport.h> 10 #include <linux/init.h> 11 #include <linux/sched.h> 12 #include <linux/pci.h> 13 #include <linux/random.h> 14 #include <linux/version.h> 15 #include <linux/mutex.h> 16 #include <linux/videodev2.h> 17 #include <linux/dma-mapping.h> 18 #include <linux/interrupt.h> 19 #include <linux/kthread.h> 20 #include <linux/highmem.h> 21 #include <linux/freezer.h> 22 #include <media/videobuf-vmalloc.h> 23 #include <media/v4l2-device.h> 24 #include <media/v4l2-ioctl.h> 25 26 static struct video_device *myvivi_device; 27 static struct timer_list myvivi_timer; 28 static struct list_head myvivi_vb_local_queue; 29 30 static void myvivi_timer_function(unsigned long data) 31 { 32 struct videobuf_buffer *vb; 33 void *vbuf; 34 struct timeval ts; 35 36 /* 1. 构造数据: 从队列头部取出第1个videobuf到本地队列中, 填充数据 37 */ 38 39 /* 1.1 从本地队列取出第1个videobuf */ 40 if (list_empty(&myvivi_vb_local_queue)) { 41 goto out; 42 } 43 44 vb = list_entry(myvivi_vb_local_queue.next, 45 struct videobuf_buffer, queue); 46 47 /* Nobody is waiting on this buffer, return */ 48 if (!waitqueue_active(&vb->done)) 49 goto out; 50 51 52 /* 1.2 填充数据 */ 53 vbuf = videobuf_to_vmalloc(vb); 54 memset(vbuf, 0xff, vb->size); 55 vb->field_count++; 56 do_gettimeofday(&ts); 57 vb->ts = ts; 58 vb->state = VIDEOBUF_DONE; 59 60 /* 1.3 把videobuf从本地队列中删除 */ 61 list_del(&vb->queue); 62 63 /* 2. 唤醒进程: 唤醒videobuf->done上的进程 */ 64 wake_up(&vb->done); 65 66 out: 67 /* 3. 修改timer的超时时间 : 30fps, 1秒里有30帧数据 68 * 每1/30 秒产生一帧数据 69 */ 70 mod_timer(&myvivi_timer, jiffies + HZ/30); 71 } 72 /* ------------------------------------------------------------------ 73 IOCTL vidioc handling 74 ------------------------------------------------------------------*/ 75 static int myvivi_videoc_querycap(struct file *file, void *priv, 76 struct v4l2_capability *cap) 77 { 78 //VIDIOC_QUERYCAP 命令通过结构 v4l2_capability 获取设备支持的操作模式: 79 /* 80 struct v4l2_capability { 81 __u8 driver[16]; i.e. "bttv" 82 __u8 card[32]; i.e. "Hauppauge WinTV" 83 __u8 bus_info[32]; "PCI:" + pci_name(pci_dev) 84 __u32 version; should use KERNEL_VERSION() 85 __u32 capabilities; Device capabilities 86 __u32 reserved[4]; 87 }; 88 * 89 */ 90 strcpy(cap->driver, "myvivi"); 91 strcpy(cap->card, "myvivi"); 92 93 cap->version = 0x0001; 94 cap->capabilities = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING; //V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING表示一个视 95 //频捕捉设备并且具有数据流控制模式 96 97 return 0; 98 } 99 100 /* 用于列举、获得、测试、设置摄像头的数据的格式 */101 /* 列举支持哪种格式 */102 static int myvivi_vidioc_enum_fmt_vid_cap(struct file *file, void *priv,103 struct v4l2_fmtdesc *f)104 {105 /*106 * F O R M A T E N U M E R A T I O N107 108 struct v4l2_fmtdesc {109 __u32 index; // Format number , 需要填充,从0开始,依次上升。110 enum v4l2_buf_type type; // buffer type Camera,则填写V4L2_BUF_TYPE_VIDEO_CAPTURE111 __u32 flags; // 如果压缩的,则Driver 填写:V4L2_FMT_FLAG_COMPRESSED,112 __u8 description[32]; // Description string ,image format的描述,如:YUV 4:2:2 (YUYV)113 __u32 pixelformat; // Format fourcc ,所支持的格式。 如:V4L2_PIX_FMT_UYVY 114 __u32 reserved[4];115 };116 */117 118 if(f->index >= 1)119 {120 return -EINVAL;121 }122 strcpy(f->description, "4:2:2, packed, YUYV");123 124 //从vivi_fmt结构体中可以看见:125 f->pixelformat = V4L2_PIX_FMT_YUYV;126 127 return 0;128 }129 struct v4l2_format myvivi_format;130 /* 返回当前所使用的格式 */131 static int myvivi_vidioc_g_fmt_vid_cap(struct file *file, void *priv,132 struct v4l2_format *f)133 {134 135 memcpy(f, &myvivi_format, sizeof(myvivi_format));136 137 return (0);138 }139 140 /* 测试驱动程序是否支持某种格式 */141 static int myvivi_vidioc_try_fmt_vid_cap(struct file *file, void *priv,142 struct v4l2_format *f)143 {144 unsigned int maxw, maxh;145 enum v4l2_field field;146 147 148 if (f->fmt.pix.pixelformat != V4L2_PIX_FMT_YUYV)149 return -EINVAL;150 151 field = f->fmt.pix.field;152 153 if (field == V4L2_FIELD_ANY) {154 field = V4L2_FIELD_INTERLACED;155 } else if (V4L2_FIELD_INTERLACED != field) {156 return -EINVAL;157 }158 159 maxw = 1024;160 maxh = 768;161 162 /*163 v4l2_format:164 struct v4l2_format { 165 enum v4l2_buf_type type; 166 union { 167 struct v4l2_pix_format pix; // V4L2_BUF_TYPE_VIDEO_CAPTURE 168 struct v4l2_window win; // V4L2_BUF_TYPE_VIDEO_OVERLAY 169 struct v4l2_vbi_format vbi; // V4L2_BUF_TYPE_VBI_CAPTURE 170 struct v4l2_sliced_vbi_format sliced; // V4L2_BUF_TYPE_SLICED_VBI_CAPTURE 171 __u8 raw_data[200]; // user-defined 172 } fmt; 173 };174 175 其中 176 enum v4l2_buf_type 177 { 178 V4L2_BUF_TYPE_VIDEO_CAPTURE = 1, 179 V4L2_BUF_TYPE_VIDEO_OUTPUT = 2, 180 V4L2_BUF_TYPE_VIDEO_OVERLAY = 3, 181 ... 182 V4L2_BUF_TYPE_PRIVATE = 0x80, 183 }; 184 185 struct v4l2_pix_format { 186 __u32 width; 187 __u32 height; 188 __u32 pixelformat; 189 enum v4l2_field field; 190 __u32 bytesperline; // for padding, zero if unused 191 __u32 sizeimage; 192 enum v4l2_colorspace colorspace; 193 __u32 priv; // private data, depends on pixelformat 194 }; 195 196 常见的捕获模式为 V4L2_BUF_TYPE_VIDEO_CAPTURE 即视频捕捉模式,在此模式下 fmt 联合体采用域 v4l2_pix_format:其中 width 为197 视频的宽、height 为视频的高、pixelformat 为视频数据格式(常见的值有 V4L2_PIX_FMT_YUV422P | V4L2_PIX_FMT_RGB565)、198 bytesperline 为一行图像占用的字节数、sizeimage 则为图像占用的总字节数、colorspace 指定设备的颜色空间。 199 */ 200 //设置最小宽度和最大宽度等201 /* 调整format的width, height, 202 * 计算bytesperline, sizeimage203 */204 v4l_bound_align_image(&f->fmt.pix.width, 48, maxw, 2, &f->fmt.pix.height, 32, maxh, 0, 0);205 206 f->fmt.pix.bytesperline =207 (f->fmt.pix.width * 16) >> 3; //颜色深度支持16208 f->fmt.pix.sizeimage =209 f->fmt.pix.height * f->fmt.pix.bytesperline;210 211 212 return 0;213 }214 215 216 static int myvivi_vidioc_s_fmt_vid_cap(struct file *file, void *priv,217 struct v4l2_format *f)218 {219 int ret = myvivi_vidioc_try_fmt_vid_cap(file, NULL, f);220 if (ret < 0)221 return ret;222 223 memcpy(&myvivi_format, f, sizeof(myvivi_format));224 225 return ret;226 }227 /* 用于列举、获得、测试、设置摄像头的数据的格式 */228 229 230 231 232 /* 队列操作1: 定义 */233 static struct videobuf_queue myvivi_vb_vidqueue;234 //自旋锁235 static spinlock_t myvivi_queue_slock;236 237 238 /* 参考documentations/video4linux/v4l2-framework.txt:239 * drivers\media\video\videobuf-core.c 240 ops->buf_setup - calculates the size of the video buffers and avoid they241 to waste more than some maximum limit of RAM;242 ops->buf_prepare - fills the video buffer structs and calls243 videobuf_iolock() to alloc and prepare mmaped memory;244 ops->buf_queue - advices the driver that another buffer were245 requested (by read() or by QBUF);246 ops->buf_release - frees any buffer that were allocated.247 248 *249 */250 251 252 253 254 /*****************buffer operations***********************/255 /* APP调用ioctl VIDIOC_REQBUFS(videobuf_reqbufs)时会导致此函数被调用,256 * 它重新调整count和size257 */258 static int myvivi_buffer_setup(struct videobuf_queue *vq, unsigned int *count, unsigned int *size)259 {260 //第一个参数为261 *size = myvivi_format.fmt.pix.sizeimage;262 263 if (0 == *count)264 *count = 32;265 266 return 0;267 }268 /* APP调用ioctl VIDIOC_QBUF时导致此函数被调用,269 * 它会填充video_buffer结构体并调用videobuf_iolock来分配内存270 * 271 */272 static int myvivi_buffer_prepare(struct videobuf_queue *vq, struct videobuf_buffer *vb,273 enum v4l2_field field)274 {275 /* 1. 做些准备工作 */276 /* 0. 设置videobuf */277 vb->size = myvivi_format.fmt.pix.sizeimage;278 vb->bytesperline = myvivi_format.fmt.pix.bytesperline;279 vb->width = myvivi_format.fmt.pix.width;280 vb->height = myvivi_format.fmt.pix.height;281 vb->field = field;282 #if 0283 /* 2. 调用videobuf_iolock为类型为V4L2_MEMORY_USERPTR的videobuf分配内存 */284 if (VIDEOBUF_NEEDS_INIT == buf->vb.state) {285 rc = videobuf_iolock(vq, &buf->vb, NULL);286 if (rc < 0)287 goto fail;288 }289 #endif290 /* 3. 设置状态 */291 vb->state = VIDEOBUF_PREPARED;292 293 return 0;294 }295 /* APP调用ioctlVIDIOC_QBUF时:296 * 1. 先调用buf_prepare进行一些准备工作297 * 2. 把buf放入队列298 * 3. 调用buf_queue(起通知作用)通知应用程序正在请求调用299 */300 static void myvivi_buffer_queue(struct videobuf_queue *vq, struct videobuf_buffer *vb)301 {302 vb->state = VIDEOBUF_QUEUED;303 304 /* 把videobuf放入本地一个队列尾部305 * 定时器处理函数就可以从本地队列取出videobuf,新增内核链表306 */307 list_add_tail(&vb->queue, &myvivi_vb_local_queue);308 }309 /* APP不再使用队列时, 用它来释放内存 */310 static void myvivi_buffer_release(struct videobuf_queue *vq,311 struct videobuf_buffer *vb)312 {313 videobuf_vmalloc_free(vb);314 vb->state = VIDEOBUF_NEEDS_INIT;315 }316 /*****************buffer operations***********************/317 318 319 320 /* 缓冲区操作: 申请/查询/放入队列/取出队列 */321 static int myvivi_vidioc_reqbufs(struct file *file, void *priv,322 struct v4l2_requestbuffers *p)323 {324 return (videobuf_reqbufs(&myvivi_vb_vidqueue, p));325 }326 static int myvivi_vidioc_querybuf(struct file *file, void *priv, struct v4l2_buffer *p)327 {328 return (videobuf_querybuf(&myvivi_vb_vidqueue, p));329 }330 static int myvivi_vidioc_qbuf(struct file *file, void *priv, struct v4l2_buffer *p)331 {332 return (videobuf_qbuf(&myvivi_vb_vidqueue, p));333 }334 static int myvivi_vidioc_dqbuf(struct file *file, void *priv, struct v4l2_buffer *p)335 {336 return (videobuf_dqbuf(&myvivi_vb_vidqueue, p,337 file->f_flags & O_NONBLOCK));338 }339 /* 缓冲区操作: 申请/查询/放入队列/取出队列 */340 /*------------------------------------------------------------------*/341 342 343 /*-------------------开启与关闭--------------------------*/344 static int myvivi_vidioc_streamon(struct file *file, void *priv, enum v4l2_buf_type i)345 {346 return videobuf_streamon(&myvivi_vb_vidqueue);347 }348 349 static int myvivi_vidioc_streamoff(struct file *file, void *priv, enum v4l2_buf_type i)350 {351 videobuf_streamoff(&myvivi_vb_vidqueue);352 return 0;353 }354 /*-------------------开启与关闭--------------------------*/355 356 357 358 359 /* ------------------------------------------------------------------360 Videobuf operations361 ------------------------------------------------------------------*/362 static struct videobuf_queue_ops myvivi_video_qops = {363 .buf_setup = myvivi_buffer_setup, /* 计算大小以免浪费 */364 .buf_prepare = myvivi_buffer_prepare,365 .buf_queue = myvivi_buffer_queue,366 .buf_release = myvivi_buffer_release,367 };368 /* ------------------------------------------------------------------369 File operations for the device370 ------------------------------------------------------------------*/371 static int myvivi_open(struct file *file)372 {373 /* 队列操作2: 初始化 */374 videobuf_queue_vmalloc_init(&myvivi_vb_vidqueue, &myvivi_video_qops,375 NULL, &myvivi_queue_slock, V4L2_BUF_TYPE_VIDEO_CAPTURE, V4L2_FIELD_INTERLACED,376 sizeof(struct videobuf_buffer), NULL); /* V4L2_BUF_TYPE_VIDEO_CAPTURE用于视频捕获设备,倒数第2个参数是buffer的头部大小 */377 //myvivi_video_qops这个结构体我们怎么去处理它呢?378 379 380 myvivi_timer.expires = jiffies + 1;381 add_timer(&myvivi_timer);382 return 0;383 }384 static int myvivi_close(struct file *file)385 {386 del_timer(&myvivi_timer);387 videobuf_stop(&myvivi_vb_vidqueue); //stop the buf388 videobuf_mmap_free(&myvivi_vb_vidqueue);389 390 return 0;391 }392 static int myvivi_mmap(struct file *file, struct vm_area_struct *vma)393 {394 return videobuf_mmap_mapper(&myvivi_vb_vidqueue, vma);395 }396 static unsigned int myvivi_poll(struct file *file, struct poll_table_struct *wait)397 {398 return videobuf_poll_stream(file, &myvivi_vb_vidqueue, wait);399 }400 /*------------------------------------------------------------------*/401 402 403 404 405 406 407 408 /*409 ------------------------------------------------------------410 struct video_device411 // device ops 412 const struct v4l2_file_operations *fops;413 ------------------------------------------------------------414 v4l2_file_operations=415 {416 struct module *owner;417 long (*ioctl) (struct file *, unsigned int, unsigned long);418 }419 420 421 422 ------------------------------------------------------------423 // callbacks 424 void (*release)(struct video_device *vdev);425 ------------------------------------------------------------426 */427 static const struct v4l2_ioctl_ops myvivi_ioctl_ops = 428 {429 //表示它是一个摄像头驱动430 .vidioc_querycap = myvivi_videoc_querycap,431 432 433 /* 用于列举、获得、测试、设置摄像头的数据的格式 */434 .vidioc_enum_fmt_vid_cap = myvivi_vidioc_enum_fmt_vid_cap,435 .vidioc_g_fmt_vid_cap = myvivi_vidioc_g_fmt_vid_cap,436 .vidioc_try_fmt_vid_cap = myvivi_vidioc_try_fmt_vid_cap,437 .vidioc_s_fmt_vid_cap = myvivi_vidioc_s_fmt_vid_cap,438 439 /* 缓冲区操作: 申请/查询/放入队列/取出队列 */440 .vidioc_reqbufs = myvivi_vidioc_reqbufs,441 .vidioc_querybuf = myvivi_vidioc_querybuf,442 .vidioc_qbuf = myvivi_vidioc_qbuf,443 .vidioc_dqbuf = myvivi_vidioc_dqbuf,444 445 // 启动/停止446 .vidioc_streamon = myvivi_vidioc_streamon,447 .vidioc_streamoff = myvivi_vidioc_streamoff, 448 449 };450 451 452 static const struct v4l2_file_operations myvivi_fops = 453 {454 .owner = THIS_MODULE,455 .open = myvivi_open,456 .release = myvivi_close,457 .mmap = myvivi_mmap,458 .poll = myvivi_poll, //提供了poll函数,还是会出现select timeout的情况,需要构造数据唤醒队列了,在poll_wait队列中休眠了459 .ioctl = video_ioctl2, /* v4l2 ioctl handler,在这个函数中设置了ioctl的用法 */460 };461 static void myvivi_release(struct video_device *vdev)462 {463 464 }465 466 static int myvivi_init(void)467 {468 int error=0;469 470 /* 1. 分配一个video_device函数,分配空间 */471 myvivi_device = video_device_alloc();472 473 /* 2. 设置 */474 475 /* 2.1 */476 myvivi_device->release = myvivi_release;477 /* 2.2 */478 myvivi_device->fops = &myvivi_fops;479 /* 2.3 */480 myvivi_device->ioctl_ops = &myvivi_ioctl_ops;481 482 483 /* 2.4 队列操作484 * a.定义/初始化一个队列(会用到一个自旋锁)485 */486 spin_lock_init(&myvivi_queue_slock);487 488 /*489 #define VFL_TYPE_GRABBER 0 //表明是一个图像采集设备-包括摄像头、调谐器490 #define VFL_TYPE_VBI 1 //从视频消隐的时间段取得信息的设备491 #define VFL_TYPE_RADIO 2 //代表无线电设备492 #define VFL_TYPE_VTX 3 //代表视传设备493 #define VFL_TYPE_MAX 4494 @nr: which device number (0 == /dev/video0, 1 == /dev/video1, ...495 -1 == first free)496 */497 /* 3.注册,第二个参数为VFL_TYPE_GRABBER, -1 为 first free */498 error = video_register_device(myvivi_device, VFL_TYPE_GRABBER, -1);499 500 501 //用定时器产生数据并唤醒进程502 init_timer(&myvivi_timer);503 myvivi_timer.function = myvivi_timer_function;504 505 506 INIT_LIST_HEAD(&myvivi_vb_local_queue);507 return error;508 };509 510 511 /*512 * 出口函数513 * 514 */515 static void myvivi_exit(void)516 {517 video_unregister_device(myvivi_device);518 video_device_release(myvivi_device);519 }520 521 522 module_init(myvivi_init);523 module_exit(myvivi_exit);524 MODULE_LICENSE("GPL");
二、虚拟摄像头驱动应用程序调用过程流程图:
虚拟摄像头一般不用自己写的程序,而是采用网络上提供的应用程序直接使用的xawtv、webcam、spcaview、luvcview;我们是采用xawtv的方式来调用一个虚拟摄像头的驱动程序,代码流程如下分析,以上驱动代码一一对应:
git ssh路径:git@git.oschina.net:linhao123/USB_CAMERA.git
http路径:https://git.oschina.net/linhao123/USB_CAMERA.git
原标题:vivi虚拟摄像头驱动程序
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