(十) 编写UVC程序
目录
编写UVC程序
这里其实自己有些也没看懂,某个函数以后要深究的话还是要看下 Linux摄像头驱动2——UVC
更多参考资料回去看 01-V4L2学习流程.md
流程简述#
回顾下要怎么写代码
1.构造一个usb_driver
2.
.id_table:
.probe:
2.1. 分配video_device:video_device_alloc
2.2. 设置
.fops
.ioctl_ops (里面需要设置11项)
如果要用内核提供的缓冲区操作函数，还需要构造一个videobuf_queue_ops
2.3. 注册: video_register_device
3.注册： usb_register
4.构造11个ioctl函数
5.构造启动,关闭函数
===============================================================================
1. open
2. 查询是否为视频设备
3. 枚举支持的格式,这里app通过下标来索引支持的格式,我们直接只返回索引1的格式,也就表示支持1种格式
4. 返回当前格式,这里构造一个全局变量,存储当前的格式
static struct v4l2_format myuvc_format;//当前格式
4. 测试是否支持某种格式
5. 设置某种格式
这里调用4的测试某种格式,然后只是复制到全局变量的当前格式中,并没有传输到硬件
6. 申请buf,这里构造了一个队列管理结构
struct myuvc_queue {
void *mem; //vmalloc_32 申请的内存地址
int count; //已经分配的buf个数
int buf_size; //每个buf的大小,这里一般为一个lcd的大小=像素*pix
struct myuvc_buffer buffer[32]; //这里的32表示最多申请32个内存
struct list_head mainqueue; /* 供APP消费用 */
struct list_head irqqueue; /* 供底层驱动生产用 */
};
struct myuvc_buffer {
struct v4l2_buffer buf;
int state; // 这个我理解其实可以和下面的vma合并
int vma_use_count; /* 表示是否已经被mmap */
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; //当前buf的的链表节点 指示 用于指示驱动
struct list_head irq; //当前buf的的链表节点 指示 用于指示app
};
myuvc_free_buffers 释放原来已经申请的缓存
mem=vmalloc_32.........申请内存
INIT_LIST_HEAD(&myuvc_queue.mainqueue);//初始化队列
INIT_LIST_HEAD(&myuvc_queue.irqqueue);
for (i = 0; i < nbuffers; ++i) {
myuvc_queue.buffer[i].buf.index = i; // 下标
myuvc_queue.buffer[i].buf.m.offset = i * bufsize; //偏移
myuvc_queue.buffer[i].state = VIDEOBUF_IDLE; //状态
...
init_waitqueue_head(&myuvc_queue.buffer[i].wait); //buf的等待队列
}
myuvc_queue.mem = mem; //起始内存地址
myuvc_queue.count = nbuffers; //几个buf,这里我们实际上限制为32个
myuvc_queue.buf_size = bufsize; //每个buf的大小
6.1 这里也就是
-[buf0]-[buf1]-----[buf32]
- v4l2_buffer
- vma_use_count 是否被mmap
- state
- wait /* APP要读某个缓冲区,如果无数据,在此休眠 */
- stream
- irq
7. 查询缓存状态
通过 myuvc_queue.buffer[v4l2_buf->index].vma_use_count和state 去更新具体的 buf的flags
8. 把缓冲区放入队列,这个具体为什么有两个队列,看老师画的图,这个函数在初始状态下应该会倍调用
1. 修改buf状态
2. 把缓冲区放入 队列中,这里有两个链表
mainqueue 给app使用,
irqqueue 给驱动使用
/* 2. 放入2个队列 */
/* 队列1: 供APP使用
*
* 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);
9. 缓存从队列中取出,这里是应用层想得到数据
// 通过当前的队列节点 找到一个节点
buf = list_first_entry(&myuvc_queue.mainqueue, struct myuvc_buffer, stream);
list_del(&buf->stream);
10. mmap,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
11. poll
buf = list_first_entry(&myuvc_queue.mainqueue, struct myuvc_buffer, stream); //找到队列
poll_wait(file, &buf->wait, wait); // 等待数据
用URB来记录一次完整传输的信息，包括每次传多少，传几次，传的目标位置等
urb 初始化
1. 分配usb_buffers,这个是实际的内存区域
myuvc_queue.urb_buffer[i] = usb_buffer_alloc(...&myuvc_queue.urb_dma[i]),//这里会返回物理地址和虚拟地址
2. 分配urb ,这个是buf的管理结构
myuvc_queue.urb[i] = usb_alloc_urb
3. 设置urb
1. 很自然的,我们需要绑定这个buf到 urb上
urb->transfer_buffer = myuvc_queue.urb_buffer[i] //虚拟地址
urb->transfer_dma = myuvc_queue.urb_dma[i]; // 物理地址
urb->complete = myuvc_video_complete; //中断函数
2. 其他设置,比如端点,一个urb应该对应了一个端点,这里一个端点对应了多个urb
urb->pipe = usb_rcvisocpipe(myuvc_udev,myuvc_bEndpointAddress);
urb 提交
for (i = 0; i < MYUVC_URBS; ++i) {
usb_submit_urb(myuvc_queue.urb[i], GFP_KERNEL)}
urb 完成中断函数
1. 状态判断
2. myuvc_queue.irqqueue 非空也就是有空的buf用于存数据
if (!list_empty(&myuvc_queue.irqqueue))
// 取出队列头
buf = list_first_entry(&myuvc_queue.irqqueue, struct myuvc_buffer, irq);
一个完整的urb是由多个包组成的,我们这里合并数据
for (i = 0; i < urb->number_of_packets; ++i)
{
src = urb->transfer_buffer + urb->iso_frame_desc[i].offset; //每包的源
dest = myuvc_queue.mem + buf->buf.m.offset + buf->buf.bytesused; //数据目的地址
..
memcpy(dest, src + src[0], nbytes); //复制到buf
}
// 删除这个buf队列,唤醒app程序,app程序应该处理完后将这个buf放回去
list_del(&buf->irq);
wake_up(&buf->wait);
3. 重新提交urb 往复循环
usb_submit_urb
12. vidioc_streamon 启动
1. 设置参数
假如我们直接设置，可能摄像头不支持我们设置的格式，后面对应的解析数据可能会出现错误。
因此我们先尝试传入设置参数，摄像头接收后会保存起来，并根据自身情况做一些修正，,这里具体的解释看代码注释 ctrl->bmHint = 1;
usb_control_msg(..这里组好数据,VS_PROBE_CONTROL),这里使用VS接口,参数VS_PROBE_CONTROL只是枚举，尝试而已，并不是设置
再将该设置读取出来
再设置
usb_control_msg(..这里组好数据,VS_COMMIT_CONTROL ),VS_PROBE_CONTROL 表示枚举参数，VS_COMMIT_CONTROL 表示提交参数
设置具体的接口的带宽等
// 一个接口下有多个设置,获得当前接口索引
myuvc_control_intf = intf->cur_altsetting->desc.bInterfaceNumber;
myuvc_streaming_intf = intf->cur_altsetting->desc.bInterfaceNumber;
//选择第8个接口设置
usb_set_interface(myuvc_udev, myuvc_streaming_intf, 8);
11个ioctl函数#
先来实现ioctl函数，参考到drivers\media\usb\uvc\uvc_driver.c中的uvc_ioctl_ops,这里的video_usercopy就是把用户空间的参数传递给内核然后执行函数
uvc_register_video
vdev->fops = &uvc_fops;
vdev->ioctl_ops = &uvc_ioctl_ops; //linux-4.13.1\drivers\media\usb\uvc\uvc_v4l2.c
uvc_fops.unlocked_ioctl
video_usercopy(file, cmd, arg, __video_do_ioctl);
vdev->ioctl_ops=uvc_ioctl_ops
// 3.x的内核是这样的,也就是最终调用 uvc_v4l2_do_ioctl
vdev->fops = &uvc_fops;
uvc_v4l2_ioctl
video_usercopy(file, cmd, arg, uvc_v4l2_do_ioctl)
针对这些具体的cmd,我们可以看到如下定义
#define VIDIOC_QUERYCAP _IOR('V', 0, struct v4l2_capability)
#define VIDIOC_RESERVED _IO('V', 1)
#define VIDIOC_ENUM_FMT _IOWR('V', 2, struct v4l2_fmtdesc)
第三个参数应该就是我们设置或者查询的结构,所以内部一般是这么使用的
struct v4l2_capability *cap = arg;
...然后对这个cap 进行设置或者解析
查询属性 VIDIOC_QUERYCAP#
// uvc_v4l2.c > uvc_v4l2_do_ioctl
case VIDIOC_QUERYCAP:
{
struct v4l2_capability *cap = arg;
memset(cap, 0, sizeof *cap);
strlcpy(cap->driver, "uvcvideo", sizeof cap->driver);
strlcpy(cap->card, vdev->name, sizeof cap->card);
usb_make_path(stream->dev->udev,
cap->bus_info, sizeof(cap->bus_info));
cap->version = LINUX_VERSION_CODE;
if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
cap->capabilities = V4L2_CAP_VIDEO_CAPTURE
| V4L2_CAP_STREAMING;
else
cap->capabilities = V4L2_CAP_VIDEO_OUTPUT
| V4L2_CAP_STREAMING;
break;
}
修改如下
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;
cap->capabilities = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
return 0;
}
枚举格式 VIDIOC_ENUM_FMT#
所谓枚举,就是App通过index=1,....max来查询我们硬件支持的格式
// uvc_v4l2.c > uvc_v4l2_do_ioctl
case VIDIOC_ENUM_FMT:
{
struct v4l2_fmtdesc *fmt = arg;
struct uvc_format *format;
enum v4l2_buf_type type = fmt->type;
__u32 index = fmt->index; //app查询的下标
if (fmt->type != stream->type ||
fmt->index >= stream->nformats)
return -EINVAL;
memset(fmt, 0, sizeof(*fmt));
fmt->index = index;
fmt->type = type;
//
format = &stream->format[fmt->index];
fmt->flags = 0;
if (format->flags & UVC_FMT_FLAG_COMPRESSED)
fmt->flags |= V4L2_FMT_FLAG_COMPRESSED;
strlcpy(fmt->description, format->name,
sizeof fmt->description);
fmt->description[sizeof fmt->description - 1] = 0;
fmt->pixelformat = format->fcc;
break;
}
这里具体的格式直接从stream->format[fmt->index]获取,这个是怎么设置的?
这个格式是16位guid，在函数\uvc_driver.c>uvc_parse_format 中的uvc_format_by_guid，可以看到这个数组uvc_fmts
static struct uvc_format_desc uvc_fmts[] = {
{
.name = "YUV 4:2:2 (YUYV)",
.guid = UVC_GUID_FORMAT_YUY2,
.fcc = V4L2_PIX_FMT_YUYV,
},
{
.name = "YUV 4:2:2 (YUYV)",
.guid = UVC_GUID_FORMAT_YUY2_ISIGHT,
.fcc = V4L2_PIX_FMT_YUYV,
},
{
.name = "YUV 4:2:0 (NV12)",
.guid = UVC_GUID_FORMAT_NV12,
.fcc = V4L2_PIX_FMT_NV12,
},
{
.name = "MJPEG",
.guid = UVC_GUID_FORMAT_MJPEG,
.fcc = V4L2_PIX_FMT_MJPEG,
},
{
.name = "YVU 4:2:0 (YV12)",
.guid = UVC_GUID_FORMAT_YV12,
.fcc = V4L2_PIX_FMT_YVU420,
},
{
.name = "YUV 4:2:0 (I420)",
.guid = UVC_GUID_FORMAT_I420,
.fcc = V4L2_PIX_FMT_YUV420,
},
{
.name = "YUV 4:2:0 (M420)",
.guid = UVC_GUID_FORMAT_M420,
.fcc = V4L2_PIX_FMT_M420,
},
{
.name = "YUV 4:2:2 (UYVY)",
.guid = UVC_GUID_FORMAT_UYVY,
.fcc = V4L2_PIX_FMT_UYVY,
},
{
.name = "Greyscale (8-bit)",
.guid = UVC_GUID_FORMAT_Y800,
.fcc = V4L2_PIX_FMT_GREY,
},
{
.name = "Greyscale (16-bit)",
.guid = UVC_GUID_FORMAT_Y16,
.fcc = V4L2_PIX_FMT_Y16,
},
{
.name = "RGB Bayer",
.guid = UVC_GUID_FORMAT_BY8,
.fcc = V4L2_PIX_FMT_SBGGR8,
},
{
.name = "RGB565",
.guid = UVC_GUID_FORMAT_RGBP,
.fcc = V4L2_PIX_FMT_RGB565,
},
{
.name = "H.264",
.guid = UVC_GUID_FORMAT_H264,
.fcc = V4L2_PIX_FMT_H264,
},
};
这里我们先只支持一种格式
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,
* 得到GUID为"59 55 59 32 00 00 10 00 80 00 00 aa 00 38 9b 71"
*/
strcpy(f->description, "4:2:2, packed, YUYV");
f->pixelformat = V4L2_PIX_FMT_YUYV;
return 0;
}
查询当前格式 VIDIOC_G_FMT#
case VIDIOC_G_FMT:
return uvc_v4l2_get_format(stream, arg);
这里我们自己直接返回定义的结构体即可
static int myuvc_vidioc_g_fmt_vid_cap(struct file *file, void *priv,
struct v4l2_format *f)
{
memcpy(f, &myuvc_format, sizeof(myuvc_format));
return (0);
}
尝试某种格式 VIDIOC_TRY_FMT#
参考: uvc_v4l2_try_format和myvivi_vidioc_try_fmt_vid_cap
case VIDIOC_TRY_FMT:
{
struct uvc_streaming_control probe;
return uvc_v4l2_try_format(stream, arg, &probe, NULL, NULL);
fmt->fmt.pix.width = frame->wWidth;
fmt->fmt.pix.height = frame->wHeight;
fmt->fmt.pix.field = V4L2_FIELD_NONE;
fmt->fmt.pix.bytesperline = format->bpp * frame->wWidth / 8;
fmt->fmt.pix.sizeimage = probe->dwMaxVideoFrameSize;
fmt->fmt.pix.colorspace = format->colorspace;
fmt->fmt.pix.priv = 0;
}
具体如下,实际我们的硬件摄像头要修改V4L2_PIX_FMT_YUYV为实际的
static struct frame_desc frames[] = {{640, 480}, {352, 288}, {320, 240}, {176, 144}, {160, 120}};
static int myuvc_vidioc_try_fmt_vid_cap(struct file *file, void *priv,
struct v4l2_format *f)
{
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 */
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;
}
设置某种格式 VIDIOC_S_FMT (未传递USB)#
case VIDIOC_S_FMT:
uvc_v4l2_set_format
uvc_v4l2_try_format(stream, fmt, &probe, &format, &frame);
memcpy(&stream->ctrl, &probe, sizeof probe);
stream->cur_format = format;
stream->cur_frame = frame;
这里并没有传输到USB,只是赋值全局变量即可
static int myuvc_vidioc_s_fmt_vid_cap(struct file *file, void *priv,
struct v4l2_format *f)
{
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;
}
队列请求 VIDIOC_REQBUFS#
case VIDIOC_REQBUFS:
uvc_alloc_buffers(&stream->queue, arg);
ret = vb2_reqbufs(&queue->queue, rb);
__vb2_queue_free
/* Release video buffer memory */
__vb2_free_mem(q, buffers);
/* Free videobuf buffers */
for (buffer = q->num_buffers - buffers; buffer < q->num_buffers;
++buffer) {
kfree(q->bufs[buffer]);
q->bufs[buffer] = NULL;
}
q->num_buffers -= buffers;
if (!q->num_buffers)
q->memory = 0;
INIT_LIST_HEAD(&q->queued_list);
这里老师的视频是2.x的内核,参考的如下
uvc_v412.c
uvc_v4l2_do_ioctl
uvc_alloc_buffers
unsigned int bufsize = PAGE_ALIGN(buflength);
unsigned int i;
void *mem = NULL;
int ret;
if (nbuffers > UVC_MAX_VIDEO_BUFFERS) /*#define UVC_MAX_VIDEO_BUFFERS 32*/
nbuffers = UVC_MAX_VIDEO_BUFFERS;
mutex_lock(&queue->mutex);
if ((ret = uvc_free_buffers(queue)) < 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;
}
for (i = 0; i < nbuffers; ++i) {
memset(&queue->buffer[i], 0, sizeof queue->buffer[i]);
queue->buffer[i].buf.index = i;
queue->buffer[i].buf.m.offset = i * bufsize;
queue->buffer[i].buf.length = buflength;
queue->buffer[i].buf.type = queue->type;
queue->buffer[i].buf.sequence = 0;
queue->buffer[i].buf.field = V4L2_FIELD_NONE;
queue->buffer[i].buf.memory = V4L2_MEMORY_MMAP;
queue->buffer[i].buf.flags = 0;
init_waitqueue_head(&queue->buffer[i].wait);
}
queue->mem = mem;
queue->count = nbuffers;
queue->buf_size = bufsize;
ret = nbuffers;
done:
mutex_unlock(&queue->mutex);
return ret;
流程基本就是
- 释放buff,如果已经有缓存就释放掉
- 申请内存头
- 清空
- 加入到两个队列
- 设置每个buf的具体的值
这里为什么需要两个队列? 因为一个是给驱动放数据用,一个是给APP取数据用的
实际代码如下
static int myuvc_vidioc_reqbufs(struct file *file, void *priv,
struct v4l2_requestbuffers *p)
{
int nbuffers = p->count;
int bufsize = PAGE_ALIGN(myuvc_format.fmt.pix.sizeimage);
unsigned int i;
void *mem = NULL;
int ret;
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;
myuvc_queue.buffer[i].buf.length = myuvc_format.fmt.pix.sizeimage;//buffer的长度（图像的大小）
myuvc_queue.buffer[i].buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;//buffer的类型（视频捕捉类）
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;
//初始化等待队列，最后的视频数据是放到一个一个缓冲区，应用程序在读某个缓冲区的时候。有可能因为缓冲区还没有数据就会休眠。缓冲区里面应该有一个队列（用来存储要读这个缓冲区的进程）
init_waitqueue_head(&myuvc_queue.buffer[i].wait);
}
myuvc_queue.mem = mem;//总buffer的地址（队列里面地址）
myuvc_queue.count = nbuffers;//队列里缓冲区的个数
myuvc_queue.buf_size = bufsize;//每个缓冲区的大小,页对齐后的大小
ret = nbuffers;
done:
return ret;
}
static int myuvc_free_buffers(void)//释放缓存
{
kfree(myuvc_queue.mem);//释放整块缓存
memset(&myuvc_queue, 0, sizeof(myuvc_queue));//清零
return 0;
}
队列查询 VIDIOC_QUERYBUF#
VIDIOC_QUERYBUF
uvc_query_buffer
vb2_querybuf(&queue->queue, buf);
__fill_v4l2_buffer(vb, b);
switch (vb->state) {
case VB2_BUF_STATE_QUEUED:
case VB2_BUF_STATE_ACTIVE:
b->flags |= V4L2_BUF_FLAG_QUEUED;
break;
case VB2_BUF_STATE_ERROR:
b->flags |= V4L2_BUF_FLAG_ERROR;
/* fall through */
case VB2_BUF_STATE_DONE:
b->flags |= V4L2_BUF_FLAG_DONE;
break;
case VB2_BUF_STATE_PREPARED:
b->flags |= V4L2_BUF_FLAG_PREPARED;
break;
case VB2_BUF_STATE_DEQUEUED:
/* nothing */
break;
}
if (__buffer_in_use(q, vb))
b->flags |= V4L2_BUF_FLAG_MAPPED;
这里3.x和2.x的内核不一样了,看下2.x的
int uvc_query_buffer(struct uvc_video_queue *queue,
struct v4l2_buffer *v4l2_buf)
{
int ret = 0;
if (v4l2_buf->index >= queue->count) {
ret = -EINVAL;
goto done;
}
__uvc_query_buffer(&queue->buffer[v4l2_buf->index], v4l2_buf);
}
static void __uvc_query_buffer(struct uvc_buffer *buf,
struct v4l2_buffer *v4l2_buf)
{
memcpy(v4l2_buf, &buf->buf, sizeof *v4l2_buf);
if (buf->vma_use_count)
v4l2_buf->flags |= V4L2_BUF_FLAG_MAPPED;
switch (buf->state) {
case UVC_BUF_STATE_ERROR:
case UVC_BUF_STATE_DONE:
v4l2_buf->flags |= V4L2_BUF_FLAG_DONE;
break;
case UVC_BUF_STATE_QUEUED:
case UVC_BUF_STATE_ACTIVE:
v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
break;
case UVC_BUF_STATE_IDLE:
default:
break;
}
}
这里我们实际代码如下
/* 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 */
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:
case VIDEOBUF_ACTIVE:
v4l2_buf->flags |= V4L2_BUF_FLAG_QUEUED;
break;
case VIDEOBUF_IDLE:
default:
break;
}
done:
return ret;
}
缓冲放入队列 VIDIOC_QBUF#
VIDIOC_QBUF
uvc_queue_buffer(&stream->queue, arg)
vb2_qbuf(&queue->queue, buf)
这个直接放上代码
static int myuvc_vidioc_qbuf(struct file *file, void *priv, struct v4l2_buffer *v4l2_buf)
{
struct myuvc_buffer *buf;
int ret;
/* 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;
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;
}
缓冲出队列 VIDIOC_DQBUF#
VIDIOC_DQBUF
uvc_dequeue_buffer
vb2_dqbuf(&queue->queue, buf, nonblocking)
/* Fill buffer information for the userspace */
__fill_v4l2_buffer(vb, b);
/* Remove from videobuf queue */
list_del(&vb->queued_entry);
dprintk(1, "dqbuf of buffer %d, with state %d\n",
vb->v4l2_buf.index, vb->state);
vb->state = VB2_BUF_STATE_DEQUEUED;
2.x的不太一样,直接放代码
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;
}
MMAP#
uvc_v4l2_mmap
uvc_queue_mmap
vb2_mmap(&queue->queue, vma)
__find_plane_by_offset
call_memop(q, mmap, vb->planes[plane].mem_priv, vma)
实际代码参考vivi好了
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
*/
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) {
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;
}
poll#
uvc_v4l2_poll
uvc_queue_poll
vb2_poll(&queue->queue, file, wait)
if (list_empty(&q->queued_list))
return POLLERR;
poll_wait(file, &q->done_wq, wait);
if (vb && (vb->state == VB2_BUF_STATE_DONE
|| vb->state == VB2_BUF_STATE_ERROR)) {
return (V4L2_TYPE_IS_OUTPUT(q->type)) ? POLLOUT | POLLWRNORM :
POLLIN | POLLRDNORM;
APP调用POLL/select来确定缓存是否就绪(有数据),我觉得在3.x内核应该直接调用vb2_poll就好了
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;
}
streamon(设置参数&urb )#
打开摄像头启动传输,这里我们需要设置参数到摄像头,怎么设置参数?流程如下
VIDIOC_STREAMON
uvc_video_enable
uvc_queue_enable(&stream->queue, 1)
vb2_streamon
uvc_commit_video(stream, &stream->ctrl)
uvc_set_video_ctrl //这里设置参数
size = stream->dev->uvc_version >= 0x0110 ? 34 : 26;
data = kzalloc(size, GFP_KERNEL);
...
__uvc_query_ctrl
usb_control_msg
uvc_init_video(stream, GFP_KERNEL)//查找端点
uvc_video_stats_start
if (intf->num_altsetting > 1)
{
uvc_find_endpoint
/* Check if the bandwidth is high enough. */
....
}
usb_set_interface //设置接口
uvc_init_video_isoc //分配设置urb
usb_submit_urb // 提交urb
那么这里的data数据是怎么构造的呢?搜索bmHint
uvc_v4l2_try_format in uvc_v4l2.c (drivers\media\video\uvc) : probe->bmHint = 1; /* dwFrameInterval */
uvc_get_video_ctrl in uvc_video.c (drivers\media\video\uvc) : ctrl->bmHint = le16_to_cpup((__le16 *)&data[0]);
uvc_set_video_ctrl in uvc_video.c (drivers\media\video\uvc) : *(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);
uvc_streaming_control in video.h (include\linux\usb) : __u16 bmHint;
可以看到可以手工设置它,也可以通过uvc_get_video_ctrl来读出后修改
uvc_get_video_ctrl
ctrl->bmHint = le16_to_cpup((__le16 *)&data[0]);
....
uvc_set_video_ctrl
*(__le16 *)&data[0] = cpu_to_le16(ctrl->bmHint);
...
我们可以这么写在2.x中,注意这里还需要选择接口的端点,也就是先
- 确定带宽
- 根据setting的endpoint能传输的wMaxPacketSize来确定选择setting
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 */
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);
/* 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: 这个端点的传输大小
* wMaxPacketSize 0x0400 1x 1024 bytes
* bAlternateSetting 8
*/
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 */
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;
}
具体的参数获取设置如下
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;
size = uvc_version >= 0x0110 ? 34 : 26;
data = kmalloc(size, GFP_KERNEL);
if (data == NULL)
return -ENOMEM;
pipe = (GET_CUR & 0x80) ? usb_rcvctrlpipe(myuvc_udev, 0)
: usb_sndctrlpipe(myuvc_udev, 0);
type |= (GET_CUR & 0x80) ? USB_DIR_IN : USB_DIR_OUT;
ret = usb_control_msg(myuvc_udev, pipe, GET_CUR, type, VS_PROBE_CONTROL << 8,
0 << 8 | myuvc_streaming_intf, data, size, 5000);
if (ret < 0)
goto done;
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; /* dwFrameInterval */
ctrl->bFormatIndex = 1;
ctrl->bFrameIndex = frame_idx + 1;
ctrl->dwFrameInterval = 333333;
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_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)
*/
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;
}
/* 参考: uvc_init_video_isoc */
static int myuvc_alloc_init_urbs(void)
{
u16 psize;
u32 size;
int npackets;
int i;
int j;
struct urb *urb;
psize = wMaxPacketSize; /* 实时传输端点一次能传输的最大字节数 */
size = myuvc_params.dwMaxVideoFrameSize; /* 一帧数据的最大长度 */
npackets = DIV_ROUND_UP(size, psize);
if (npackets > 32)
npackets = 32;
size = myuvc_queue.urb_size = psize * npackets;
for (i = 0; i < MYUVC_URBS; ++i) {
/* 1. 分配usb_buffers */
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;
urb->pipe = usb_rcvisocpipe(myuvc_udev,myuvc_bEndpointAddress);
urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
urb->interval = 1;
urb->transfer_buffer = myuvc_queue.urb_buffer[i];
urb->transfer_dma = myuvc_queue.urb_dma[i];
urb->complete = myuvc_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;
}
}
return 0;
}
streamoff#
uvc_video_enable
uvc_uninit_video(stream, 1);
usb_set_interface(stream->dev->udev, stream->intfnum, 0);
uvc_queue_enable(&stream->queue, 0);
uvc_video_clock_cleanup(stream);
这个就比较简单,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 */
usb_set_interface(myuvc_udev, myuvc_streaming_intf, 0);
return 0;
}
设置URB#
在上面的streamon中其实已经提到了设置urb,具体参考uvc_init_video_isoc
VIDIOC_STREAMON
uvc_video_enable
uvc_queue_enable(&stream->queue, 1)
vb2_streamon
uvc_commit_video(stream, &stream->ctrl)
uvc_set_video_ctrl //这里设置参数
size = stream->dev->uvc_version >= 0x0110 ? 34 : 26;
data = kzalloc(size, GFP_KERNEL);
...
__uvc_query_ctrl
usb_control_msg
uvc_init_video(stream, GFP_KERNEL)//查找端点
uvc_video_stats_start
if (intf->num_altsetting > 1)
{
uvc_find_endpoint
/* Check if the bandwidth is high enough. */
....
}
usb_set_interface //设置接口
uvc_init_video_isoc //分配设置urb-----------
usb_submit_urb // 提交urb
uvc_init_video_isoc
uvc_alloc_urb_buffers //存储数据的缓冲区
usb_alloc_coherent ===这个和以前的函数 usb_buffer_alloc等同
for (i = 0; i < UVC_URBS; ++i)
kmalloc(stream->urb_size, gfp_flags | __GFP_NOWARN);
//===这个和以前的函数 usb_buffer_alloc等同
static inline void *usb_buffer_alloc
return usb_alloc_coherent(dev, size, mem_flags, dma);
for (i = 0; i < UVC_URBS; ++i) {
urb = usb_alloc_urb(npackets, gfp_flags); //管理结构,有一个指针指向上面的缓冲区
if (urb == NULL) {
uvc_uninit_video(stream, 1);
return -ENOMEM;
}
实际的代码如下
/* 参考: uvc_init_video_isoc */
static int myuvc_alloc_init_urbs(void)
{
u16 psize;
u32 size;
int npackets;
int i;
int j;
struct urb *urb;
psize = wMaxPacketSize; /* 实时传输端点一次能传输的最大字节数 */
size = myuvc_params.dwMaxVideoFrameSize; /* 一帧数据的最大长度 */
npackets = DIV_ROUND_UP(size, psize);
if (npackets > 32)
npackets = 32;
size = myuvc_queue.urb_size = psize * npackets;
for (i = 0; i < MYUVC_URBS; ++i) {
/* 1. 分配usb_buffers */
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;
//myuvc_bEndpointAddress 这个是端点,我们选择了接口下的某个设置,就会有一个端点地址
urb->pipe = usb_rcvisocpipe(myuvc_udev,myuvc_bEndpointAddress);//管道设置
urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
urb->interval = 1;//端点描述符里面的bInterval
urb->transfer_buffer = myuvc_queue.urb_buffer[i];//分配的是哪一个urb_buffer
urb->transfer_dma = myuvc_queue.urb_dma[i];
urb->complete = myuvc_video_complete;//驱动程序收到一个urb包后，会产生一个中断，这是相应的中断处理函数
urb->number_of_packets = npackets;//urb要传输多少次数据
urb->transfer_buffer_length = size;//总共是多长的数据
//每一次传输的数据存在在哪里（偏移地址和长度）
for (j = 0; j < npackets; ++j) {
urb->iso_frame_desc[j].offset = j * psize;
urb->iso_frame_desc[j].length = psize;
}
}
return 0;
}
URB中断处理函数#
参考代码
uvc_video_complete
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);// 从urb取出数据
if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
ret);
}
}
解析函数搜索下 decode > uvc_video_decode_isoc
uvc_video_init
if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
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;
else
stream->decode = uvc_video_decode_bulk;
实际代码如下,这个是每个urb就会触发的,一个完整的数据一般由多个urb组成
/* 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);
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;
}
src = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
dest = myuvc_queue.mem + buf->buf.m.offset + buf->buf.bytesused;
len = urb->iso_frame_desc[i].actual_length;
/* 判断数据是否有效 */
/* URB数据含义:
* data[0] : 头部长度
* data[1] : 错误状态
*/
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;
}
/* 除去头部后的数据长度 */
len -= src[0];
/* 缓冲区最多还能存多少数据 */
maxlen = buf->buf.length - buf->buf.bytesused;
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 */
if (len > maxlen) {
buf->state = VIDEOBUF_DONE;
}
/* Mark the buffer as done if the EOF marker is set. */
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);
}
}
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