3.1 mxc_v4l2_capture.c分析---probe函数分析
mxc_v4l2_capture.c函数提供了应用程序中的一些接口函数，所以从分析它开始：
（一）看一个驱动程序从它的入口函数开始：
module_init(camera_init);
static __init int camera_init(void)
{
u8 err = 0;
pr_debug("In MVC:camera_init\n");
/* Register the device driver structure. */
err = platform_driver_register(&mxc_v4l2_driver);
if (err != 0) {
pr_err("ERROR: v4l2 capture:camera_init: "
"platform_driver_register failed.\n");
return err;
}
return err;
}它里面就一个重要的函数，platform_driver_register(&mxc_v4l2_driver)；通过调用这个函数，将mxc_v4l2_driver这个驱动注册到platform总线上面，然后当总线中有对应的设备的时候，就会调用这个mxc_v4l2_driver结构体里面的的probe函数mxc_v4l2_probe。mxc_v4l2_driver结构体如下所示：
static struct platform_driver mxc_v4l2_driver = {
.driver = {
.name = "mxc_v4l2_capture",
.owner = THIS_MODULE,
.of_match_table = mxc_v4l2_dt_ids,
},
.id_table = imx_v4l2_devtype,
.probe = mxc_v4l2_probe,
.remove = mxc_v4l2_remove,
.suspend = mxc_v4l2_suspend,
.resume = mxc_v4l2_resume,
.shutdown = NULL,
};（二） mxc_v4l2_probe函数
static int mxc_v4l2_probe(struct platform_device *pdev)
{
/* Create cam and initialize it. */
cam_data *cam = kmalloc(sizeof(cam_data), GFP_KERNEL);
if (cam == NULL) {
pr_err("ERROR: v4l2 capture: failed to register camera\n");
return -1;
}
init_camera_struct(cam, pdev);
pdev->dev.release = camera_platform_release;
/* Set up the v4l2 device and register it*/
cam->self->priv = cam;
v4l2_int_device_register(cam->self);
/* register v4l video device */
if (video_register_device(cam->video_dev, VFL_TYPE_GRABBER, video_nr)
< 0) {
kfree(cam);
cam = NULL;
pr_err("ERROR: v4l2 capture: video_register_device failed\n");
return -1;
}
pr_debug(" Video device registered: %s #%d\n",
cam->video_dev->name, cam->video_dev->minor);
if (device_create_file(&cam->video_dev->dev,
&dev_attr_fsl_v4l2_capture_property))
dev_err(&pdev->dev, "Error on creating sysfs file"
" for capture\n");
if (device_create_file(&cam->video_dev->dev,
&dev_attr_fsl_v4l2_overlay_property))
dev_err(&pdev->dev, "Error on creating sysfs file"
" for overlay\n");
if (device_create_file(&cam->video_dev->dev,
&dev_attr_fsl_csi_property))
dev_err(&pdev->dev, "Error on creating sysfs file"
" for csi number\n");
return 0;
}这个函数首先为cam_data*cam分配内存，然后就调用init_camera_struct(cam,pdev);函数来对cam结构体进行初始化。
2.1 init_camera_struct函数
static int init_camera_struct(cam_data *cam, struct platform_device *pdev)
{
const struct of_device_id *of_id =
of_match_device(mxc_v4l2_dt_ids, &pdev->dev);
struct device_node *np = pdev->dev.of_node;
int ipu_id, csi_id, mclk_source;
int ret = 0;
struct v4l2_device *v4l2_dev;
pr_debug("In MVC: init_camera_struct\n");
ret = of_property_read_u32(np, "ipu_id", &ipu_id);
if (ret) {
dev_err(&pdev->dev, "ipu_id missing or invalid\n");
return ret;
}
ret = of_property_read_u32(np, "csi_id", &csi_id);
if (ret) {
dev_err(&pdev->dev, "csi_id missing or invalid\n");
return ret;
}
ret = of_property_read_u32(np, "mclk_source", &mclk_source);
if (ret) {
dev_err(&pdev->dev, "sensor mclk missing or invalid\n");
return ret;
}
/* Default everything to 0 */
memset(cam, 0, sizeof(cam_data));
/* get devtype to distinguish if the cpu is imx5 or imx6
* IMX5_V4L2 specify the cpu is imx5
* IMX6_V4L2 specify the cpu is imx6q or imx6sdl
*/
if (of_id)
pdev->id_entry = of_id->data;
cam->devtype = pdev->id_entry->driver_data;
cam->ipu = ipu_get_soc(ipu_id);
if (cam->ipu == NULL) {
pr_err("ERROR: v4l2 capture: failed to get ipu\n");
return -EINVAL;
} else if (cam->ipu == ERR_PTR(-ENODEV)) {
pr_err("ERROR: v4l2 capture: get invalid ipu\n");
return -ENODEV;
}
init_MUTEX(&cam->param_lock);
init_MUTEX(&cam->busy_lock);
cam->video_dev = video_device_alloc();
if (cam->video_dev == NULL)
return -ENODEV;
*(cam->video_dev) = mxc_v4l_template;
video_set_drvdata(cam->video_dev, cam);
dev_set_drvdata(&pdev->dev, (void *)cam);
cam->video_dev->minor = -1;
v4l2_dev = kzalloc(sizeof(*v4l2_dev), GFP_KERNEL);
if (!v4l2_dev) {
dev_err(&pdev->dev, "failed to allocate v4l2_dev structure\n");
video_device_release(cam->video_dev);
return -ENOMEM;
}
if (v4l2_device_register(&pdev->dev, v4l2_dev) < 0) {
dev_err(&pdev->dev, "register v4l2 device failed\n");
video_device_release(cam->video_dev);
kfree(v4l2_dev);
return -ENODEV;
}
cam->video_dev->v4l2_dev = v4l2_dev;
init_waitqueue_head(&cam->enc_queue);
init_waitqueue_head(&cam->still_queue);
/* setup cropping */
cam->crop_bounds.left = 0;
cam->crop_bounds.width = 640;
cam->crop_bounds.top = 0;
cam->crop_bounds.height = 480;
cam->crop_current = cam->crop_defrect = cam->crop_bounds;
ipu_csi_set_window_size(cam->ipu, cam->crop_current.width,
cam->crop_current.height, cam->csi);
ipu_csi_set_window_pos(cam->ipu, cam->crop_current.left,
cam->crop_current.top, cam->csi);
cam->streamparm.parm.capture.capturemode = 0;
cam->standard.index = 0;
cam->standard.id = V4L2_STD_UNKNOWN;
cam->standard.frameperiod.denominator = 30;
cam->standard.frameperiod.numerator = 1;
cam->standard.framelines = 480;
cam->standard_autodetect = true;
cam->streamparm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
cam->streamparm.parm.capture.timeperframe = cam->standard.frameperiod;
cam->streamparm.parm.capture.capability = V4L2_CAP_TIMEPERFRAME;
cam->overlay_on = false;
cam->capture_on = false;
cam->v4l2_fb.flags = V4L2_FBUF_FLAG_OVERLAY;
cam->v2f.fmt.pix.sizeimage = 352 * 288 * 3 / 2;
cam->v2f.fmt.pix.bytesperline = 288 * 3 / 2;
cam->v2f.fmt.pix.width = 288;
cam->v2f.fmt.pix.height = 352;
cam->v2f.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;
cam->win.w.width = 160;
cam->win.w.height = 160;
cam->win.w.left = 0;
cam->win.w.top = 0;
cam->ipu_id = ipu_id;
cam->csi = csi_id;
cam->mclk_source = mclk_source;
cam->mclk_on[cam->mclk_source] = false;
cam->enc_callback = camera_callback;
init_waitqueue_head(&cam->power_queue);
spin_lock_init(&cam->queue_int_lock);
spin_lock_init(&cam->dqueue_int_lock);
cam->self = kmalloc(sizeof(struct v4l2_int_device), GFP_KERNEL);
cam->self->module = THIS_MODULE;
sprintf(cam->self->name, "mxc_v4l2_cap%d", cam->csi);
cam->self->type = v4l2_int_type_master;
cam->self->u.master = &mxc_v4l2_master;
return 0;
}2.1.1 首先通过of_match_device函数根据pdev->dev里面的of_node项，从mxc_v4l2_dt_ids数组里面找出最匹配的一项of_device_id，然后将这个值赋给of_id。在这里of_id= {
.compatible= "fsl,imx6q-v4l2-capture",
.data= &imx_v4l2_devtype[IMX6_V4L2],
},
2.1.2 然后通过三个of_property_read_u32函数，来分别读取pdev->dev.of_node里面的"ipu_id"，"csi_id"和"mclk_source"的值，并将他们分别保存在ipu_id和csi_id以及mclk_source中。之后调用memset将cam_data*cam中的其他变量设置为0.
然后通过pdev->id_entry= of_id->data;将pdev中的id_entry项设置为of_id->data。在这里就是pdev->id_entry= &imx_v4l2_devtype[IMX6_V4L2].
然后就是cam->devtype=pdev->id_entry->driver_data;通过上一步，刚把pdev里面的id_entry赋值，所以这一步，就是将cam->devtype的值设置为IMX6_V4L2。
2.1.3 之后就是cam->ipu= ipu_get_soc(ipu_id); ipu_get_soc这个函数在ipu_common.c中定义，如下所示：
struct ipu_soc *ipu_get_soc(int id)
{
if (id >= MXC_IPU_MAX_NUM)
return ERR_PTR(-ENODEV);
else if (!ipu_array[id].online)
return ERR_PTR(-ENODEV);
else
return &(ipu_array[id]);
}
EXPORT_SYMBOL_GPL(ipu_get_soc);其中这个ipu_array数组可以搜索看到，是在前面定义的一个全局数组，如下：
static struct ipu_soc ipu_array[MXC_IPU_MAX_NUM];
#define MXC_IPU_MAX_NUM 2目前为止，最多有2个ipu，ipu_get_soc函数从这个ipu_array数组中根据ipu_id取出相应的ipu。然后对ipu_id进行判断，如果它大于ipu的最大数目，就直接返回。然后判断ipu_array[id].online这一项，我们可以在ipu_soc结构体里面看到这一项，他是一个bool类型的变量，判断系统是否正在占用这一个ipu，如果系统正在占用这一个ipu的话，就只能返回了，如果以上两点都满足的话，就返回找到的这个ipu_soc结构体的地址。可以看这个cam_data结构体，它里面有一项成员是void*ipu，所以这个ipu_get_soc返回的是（structipu_soc *）类型。在本例中就是返回&(ipu_array[id])。
在这个ipu_soc函数中，它会返回成功的地址或者-ENODEV出错提示，在init_camera_struct函数中，它对这个函数的返回值进行了判断，如下所示：
cam->ipu = ipu_get_soc(ipu_id);
if (cam->ipu == NULL) {
pr_err("ERROR: v4l2 capture: failed to get ipu\n");
return -EINVAL;
} else if (cam->ipu == ERR_PTR(-ENODEV)) {
pr_err("ERROR: v4l2 capture: get invalid ipu\n");
return -ENODEV;
}2.1.4 之后就是初始化一些互斥锁，为cam结构体里面的video_dev分配内存，然后通过*(cam->video_dev)= mxc_v4l_template;将video_device结构体指向了mxc_v4l_template，mxc_v4l_template如下所示：
static struct video_device mxc_v4l_template = {
.name = "Mxc Camera",
.fops = &mxc_v4l_fops,
.release = video_device_release,
};static struct v4l2_file_operations mxc_v4l_fops = {
.owner = THIS_MODULE,
.open = mxc_v4l_open,
.release = mxc_v4l_close,
.read = mxc_v4l_read,
.ioctl = mxc_v4l_ioctl,
.mmap = mxc_mmap,
.poll = mxc_poll,
};通过这一步，就为用户空间提供了接口函数，当用户空间调用open,read, poll等函数的时候，就会调用到mxc_v4l_open,mxc_v4l_read, mxc_v4l_poll等函数。这些函数都在mxc_v4l2_capture.c里面提供了，后面再分析。
2.1.5 然后通过
video_set_drvdata(cam->video_dev, cam);
dev_set_drvdata(&pdev->dev, (void *)cam);这两个函数，分别将cam结构体设置为cam->video_dev和&pdev->dev里面的私有数据。即将cam->video_dev->dev->p->driver_data指向cam和将&pdev->dev->p->driver_data指向cam。
这两个函数就不具体分析了。
2.1.6 然后将cam->video_dev->minor设置为-1;在structvideo_device结构体中有这样的注释：
/*'minor' is set to -1 if the registration failed */，
因为我们现在在init_camera_struct函数中，初始化的时候也把这个值设置成初始值。
2.1.7 之后就是为v4l2_dev结构体分配内存并清零，调用了v4l2_device_register(&pdev->dev,v4l2_dev)函数，这个函数将v4l2_dev这个结构体里面的一些成员函数进行了初始化，然后将pdev->dev->p指向v4l2_dev，然后通过cam->video_dev->v4l2_dev= v4l2_dev;将v4l2_dev添加到cam->video_dev结构体里面。
2.1.8 通过
init_waitqueue_head(&cam->enc_queue);
init_waitqueue_head(&cam->still_queue);这两条语句，初始化cam结构体里面的这两个队列头，这两个队列在用到的时候再分析。
2.1.9 之后就是设置cam_data结构体里面的一些其他参数的初始值：
cam->crop_bounds.left = 0;
cam->crop_bounds.width = 640;
cam->crop_bounds.top = 0;
cam->crop_bounds.height = 480;首先设置的是crop_bounds的值，也就是图像裁剪的大小和位置，这个结构体是v4l2_rect类型的,
struct v4l2_rect {
__s32 left;
__s32 top;
__u32 width;
__u32 height;
};为什么这个结构体采用这四个值呢？可以想象一下，如果想要裁剪显示屏幕上任意一块区域，只需要知道这一块区域的左上角坐标，同时知道区域的宽度和高度，这块区域其他3个点的坐标位置就可以通过这几个值计算出来。
然后通过cam->crop_current= cam->crop_defrect =cam->crop_bounds;这条语句将cam_data结构体里面其他两个相似的成员crop_current和crop_defrect赋值。将这三个值都初始化为左上角坐标为（0，0），区域大小都为640* 480。
之后通过ipu_csi_set_window_size(cam->ipu,cam->crop_current.width,
cam->crop_current.height,cam->csi);
函数来设置显示窗口的大小范围，这个ipu_csi_set_window_size函数在ipu_capture.c中定义，先简略分析一下，核心就是下面这个函数：
ipu_csi_write(ipu,csi, (width - 1) | (height - 1) << 16, CSI_ACT_FRM_SIZE);
--->writel(value, ipu->csi_reg[csi] + offset);
其中value= (width - 1) | (height - 1) << 16, offset = CSI_ACT_FRM_SIZE，大致意思是根据cam->ipu和cam->csi（这两个变量之前刚设定好）将(width- 1) | (height - 1) <<16的值写到csi寄存器里面，这个csi寄存器的初始地址在通过ipu_get_soc函数获取ipu的时候已经获取到了，CSI_ACT_FRM_SIZE就是关于csi寄存器初始地址的偏移值，它在drivers/mxc/ipu3/ipu_regs.h中定义。
之后就是ipu_csi_set_window_pos(cam->ipu,cam->crop_current.left,
cam->crop_current.top,cam->csi);
函数，这个函数同样在ipu_capture.c中定义，它会根据ipu和csi的值，设置底层的寄存器的值。
即上面设置了crop_bounds的4个初始值，然后就调用ipu_csi_set_window_size和ipu_csi_set_window_pos将这四个值写到底层的寄存器中去。
2.1.10 下面就是继续设置cam_data结构体里面成员初始值，分别设置了streamparm，standard，standard_autodetect，overlay_on，capture_on，v2f，win的值。这些就不分析了，后面用到的话再说。
然后继续设置其他值：
cam->ipu_id = ipu_id;
cam->csi = csi_id;
cam->mclk_source = mclk_source;
cam->mclk_on[cam->mclk_source] = false;比较重要的是下面这个：
cam->enc_callback=camera_callback;设置cam_data结构体中的enc_callback回调函数，这个函数在本文件中定义，它是一个中断处理函数，在视频采集过程中，如果一个buffer填充满的话，会产生一个中断信号，中断处理函数中最终会调用到这个函数来处理中断。
2.1.11 下面就是设置cam_data中的self结构体，self结构体为structv4l2_int_device类型的,
cam->self = kmalloc(sizeof(struct v4l2_int_device), GFP_KERNEL);
cam->self->module = THIS_MODULE;
sprintf(cam->self->name, "mxc_v4l2_cap%d", cam->csi);
cam->self->type = v4l2_int_type_master;
cam->self->u.master = &mxc_v4l2_master;首先分配内存，将module指向THIS_MODULE，然后将名字根据csi号设置为mxc_v4l2_cap%d的类型，分别设置self的type和u.master类型。将这个cam->self结构体作为一个master设备注册到int_list链表中。
至此，这个cam_data结构体初始化完毕了，这个结构体toobig了～～～
2.2 下面我们返回probe函数中继续分析：
pdev->dev.release= camera_platform_release;
为device结构体中指定release函数，但是这个函数中什么都没有做，如果不添加这个函数的话就会报错，所以就添加一个空函数进去。
2.3 下面是
cam->self->priv= cam;
v4l2_int_device_register(cam->self);
cam_data结构体中self变量是v4l2_int_device类型的，首先将cam保存为v4l2_int_deviceself的私有数据，然后在操作cam->self结构体的时候，在很多函数中，行参只是v4l2_int_device类型的self，相要获得更外层的cam_data结构体的话，就可以从self->priv中获取。然后调用v4l2_int_device_register函数来注册v4l2_int_device。
这个函数在v4l2-int-device.c中定义，如下所示：
int v4l2_int_device_register(struct v4l2_int_device *d)
{
if (d->type == v4l2_int_type_slave)
sort(d->u.slave->ioctls, d->u.slave->num_ioctls, /* 按照序号存储,加快访问速度。*/
sizeof(struct v4l2_int_ioctl_desc),
&ioctl_sort_cmp, NULL);
mutex_lock(&mutex);
list_add(&d->head, &int_list); //无论是slave还是master都会添加到int_list中
v4l2_int_device_try_attach_all(); //都会做匹配动作
mutex_unlock(&mutex);
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_int_device_register);在前一节中已经具体分析这个v4l2设备中master和slave的注册过程了，在这里就不再具体分析。
2.4下面是这个probe函数的核心函数：video_register_device，它在v4l2-dev.h中定义，如下所示：
static inline int __must_check video_register_device_no_warn(
struct video_device *vdev, int type, int nr)
{
return __video_register_device(vdev, type, nr, 0, vdev->fops->owner);
}__video_register_device在v4l2-dev.c中定义：（就直接在代码中注释了）
int __video_register_device(struct video_device *vdev, int type, int nr,
int warn_if_nr_in_use, struct module *owner)
{
int i = 0;
int ret;
int minor_offset = 0;
int minor_cnt = VIDEO_NUM_DEVICES;
const char *name_base;
/* A minor value of -1 marks this video device as never
having been registered */
vdev->minor = -1;
/* the release callback MUST be present */
if (WARN_ON(!vdev->release))
return -EINVAL; /*如果没有提供这个release函数的话，就直接返回错误，那么我们在哪初始化了它呢？在上面的init_camera_struct(cam,pdev);函数中，通过下面这个语句*(cam->video_dev)= mxc_v4l_template;来为它指定release函数了，在mxc_v4l_template结构体中
.release= video_device_release。*/
caseVFL_TYPE_GRABBER:
/* the v4l2_dev pointer MUST be present */
if (WARN_ON(!vdev->v4l2_dev))
return -EINVAL;/*这个v4l2_dev指针也是必须要提供的，它同样在init_camera_struct函数中提供了*/
/* v4l2_fh support */
spin_lock_init(&vdev->fh_lock);
INIT_LIST_HEAD(&vdev->fh_list);
/* Part 1: check device type */
switch (type) {
case VFL_TYPE_GRABBER:
name_base = "video";
break;
case VFL_TYPE_VBI:
name_base = "vbi";
break;
case VFL_TYPE_RADIO:
name_base = "radio";
break;
case VFL_TYPE_SUBDEV:
name_base = "v4l-subdev";
break;
default:
printk(KERN_ERR "%s called with unknown type: %d\n",
__func__, type);
return -EINVAL;
} /*根据传进来的type参数，确定设备在/dev目录下看到的名字*/
vdev->vfl_type = type;
vdev->cdev = NULL;
if (vdev->v4l2_dev) {
if (vdev->v4l2_dev->dev)
vdev->parent = vdev->v4l2_dev->dev;
if (vdev->ctrl_handler == NULL)
vdev->ctrl_handler = vdev->v4l2_dev->ctrl_handler;
/* If the prio state pointer is NULL, then use the v4l2_device
prio state. */
if (vdev->prio == NULL)
vdev->prio = &vdev->v4l2_dev->prio;
} /*进行vdev中父设备和ctrl处理函数的初始化。*/
/* Part 2: find a free minor, device node number and device index. */
#ifdef CONFIG_VIDEO_FIXED_MINOR_RANGES
/* Keep the ranges for the first four types for historical
* reasons.
* Newer devices (not yet in place) should use the range
* of 128-191 and just pick the first free minor there
* (new style). */
switch (type) {
case VFL_TYPE_GRABBER:
minor_offset = 0;
minor_cnt = 64;
break;
case VFL_TYPE_RADIO:
minor_offset = 64;
minor_cnt = 64;
break;
case VFL_TYPE_VBI:
minor_offset = 224;
minor_cnt = 32;
break;
default:
minor_offset = 128;
minor_cnt = 64;
break;
}
#endif
/* Pick a device node number */
mutex_lock(&videodev_lock);
nr = devnode_find(vdev, nr == -1 ? 0 : nr, minor_cnt);
if (nr == minor_cnt)
nr = devnode_find(vdev, 0, minor_cnt);
if (nr == minor_cnt) {
printk(KERN_ERR "could not get a free device node number\n");
mutex_unlock(&videodev_lock);
return -ENFILE;
}
#ifdef CONFIG_VIDEO_FIXED_MINOR_RANGES
/* 1-on-1 mapping of device node number to minor number */
i = nr;
#else
/* The device node number and minor numbers are independent, so
we just find the first free minor number. */
for (i = 0; i < VIDEO_NUM_DEVICES; i++)
if (video_device[i] == NULL)
break;
if (i == VIDEO_NUM_DEVICES) {
mutex_unlock(&videodev_lock);
printk(KERN_ERR "could not get a free minor\n");
return -ENFILE;
}
#endif
vdev->minor = i + minor_offset;
vdev->num = nr;
devnode_set(vdev);
/* Should not happen since we thought this minor was free */
WARN_ON(video_device[vdev->minor] != NULL);
vdev->index = get_index(vdev);
video_device[vdev->minor] = vdev;
mutex_unlock(&videodev_lock);
if (vdev->ioctl_ops)
determine_valid_ioctls(vdev);/*上面的part2就是确定设备的次设备号*/
/* Part 3: Initialize the character device */
vdev->cdev = cdev_alloc();
if (vdev->cdev == NULL) {
ret = -ENOMEM;
goto cleanup;
} /*在这进行设备的注册，用cdev_alloc函数，从这我们就可以看出来，它是一个普通的字符设备驱动，然后设置它的一些参数。怎么就是字符设备驱动了？？？这个通过v4l2框架中可以看出来。*/
vdev->cdev->ops = &v4l2_fops; /*cdev结构体里面的ops指向了v4l2_fops这个结构体，这个v4l2_fops结构体也是在v4l2-dev.c这个文件中。它是一个file_operations操作函数集，
static const struct file_operations v4l2_fops = {
.owner = THIS_MODULE,
.read = v4l2_read,
.write = v4l2_write,
.open = v4l2_open,
.get_unmapped_area = v4l2_get_unmapped_area,
.mmap = v4l2_mmap,
.unlocked_ioctl = v4l2_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = v4l2_compat_ioctl32,
#endif
.release = v4l2_release,
.poll = v4l2_poll,
.llseek = no_llseek,
};仔细分析上面那些子函数的话，就可以发现他们最终还是调用的是cam->video_dev所提供的函数，即
mxc_v4l_template结构体里面的mxc_v4l_fops。
*/
vdev->cdev->owner = owner;
ret = cdev_add(vdev->cdev, MKDEV(VIDEO_MAJOR, vdev->minor), 1);
if (ret < 0) {
printk(KERN_ERR "%s: cdev_add failed\n", __func__);
kfree(vdev->cdev);
vdev->cdev = NULL;
goto cleanup;
}
/* Part 4: register the device with sysfs */
vdev->dev.class = &video_class;
vdev->dev.devt = MKDEV(VIDEO_MAJOR, vdev->minor);
if (vdev->parent)
vdev->dev.parent = vdev->parent;
dev_set_name(&vdev->dev, "%s%d", name_base, vdev->num);
ret = device_register(&vdev->dev);
if (ret < 0) {
printk(KERN_ERR "%s: device_register failed\n", __func__);
goto cleanup;
}
/* Register the release callback that will be called when the last
reference to the device goes away. */
vdev->dev.release = v4l2_device_release;
if (nr != -1 && nr != vdev->num && warn_if_nr_in_use)
printk(KERN_WARNING "%s: requested %s%d, got %s\n", __func__,
name_base, nr, video_device_node_name(vdev));
/* Increase v4l2_device refcount */
if (vdev->v4l2_dev)
v4l2_device_get(vdev->v4l2_dev);
/* 在sysfs中创建类，在类下创建设备结点 */
#if defined(CONFIG_MEDIA_CONTROLLER)
/* Part 5: Register the entity. */
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV) {
vdev->entity.type = MEDIA_ENT_T_DEVNODE_V4L;
vdev->entity.name = vdev->name;
vdev->entity.info.v4l.major = VIDEO_MAJOR;
vdev->entity.info.v4l.minor = vdev->minor;
ret = media_device_register_entity(vdev->v4l2_dev->mdev,
&vdev->entity);
if (ret < 0)
printk(KERN_WARNING
"%s: media_device_register_entity failed\n",
__func__);
}
#endif /*创建实体entity，这一步并不是必须的，需要配置了CONFIG_MEDIA_CONTROLLER选项后才会执行这一步，在这一步里面有一个media_entity实体结构体，在后面再分析它。*/
/* Part 6: Activate this minor. The char device can now be used. */
set_bit(V4L2_FL_REGISTERED, &vdev->flags); /*设置标志位*/
mutex_lock(&videodev_lock);
video_device[vdev->minor] = vdev; /*将设置好的video_device结构体vdev按照次设备号保存到video_device数组中。这个数组是在前面staticstruct video_device *video_device[VIDEO_NUM_DEVICES];定义的。*/
mutex_unlock(&videodev_lock);
return 0;
cleanup:
mutex_lock(&videodev_lock);
if (vdev->cdev)
cdev_del(vdev->cdev);
devnode_clear(vdev);
mutex_unlock(&videodev_lock);
/* Mark this video device as never having been registered. */
vdev->minor = -1;
return ret;
}
EXPORT_SYMBOL(__video_register_device);2.5 下面通过3次调用device_create_file函数，来分别为dev_attr_fsl_v4l2_capture_property，dev_attr_fsl_v4l2_overlay_property和dev_attr_fsl_csi_property在/sys/class/下创建对应的属性文件。
至此，mxc_v4l2_probe函数就分析完毕了。