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视频驱动V4L2子系统驱动架构 - ioctl

發布時間：2025/3/21 windows 25 豆豆

生活随笔收集整理的這篇文章主要介紹了视频驱动V4L2子系统驱动架构 - ioctl 小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

基于linux4.6.3,最后會附上一張ioctl調用總圖，分析代碼還是要用圖來說明，這樣更清晰一點，我就是這么分析的，不過平時分析的圖很隨便，而且很大，所以就不能在這里呈現，我在這里會貼出一個簡略圖

ioctl詳解

進入ioctl都是從cdev->ops->ioctl進入的，一般的驅動cdev都是驅動自己初始化的，在v4l2架構中，cdev都已經初始化完成，不需要驅動開發者來初始化，下面是v4l2的cdev->ops結構體v4l2_fops ：

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, };

可以看到ioctl有兩個，一個unlocked_ioctl，另一個是compat_ioctl 兼容性的，其中的區別這里不多說，我們來看函數v4l2_ioctl：

static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) {struct video_device *vdev = video_devdata(filp);int ret = -ENODEV;if (vdev->fops->unlocked_ioctl) {struct mutex *lock = v4l2_ioctl_get_lock(vdev, cmd);if (lock && mutex_lock_interruptible(lock))return -ERESTARTSYS;if (video_is_registered(vdev))ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);--正常進入函數|video_device->fopsif (lock)mutex_unlock(lock);} elseret = -ENOTTY;return ret; }

從上可以看到要調用vdev->fops->unlocked_ioctl(filp, cmd, arg);具體驅動實現不同，以davinci平臺為例來介紹，在vpfe_capture.c文件中，初始化過程中有

vfd->fops = &vpfe_fops;

static const struct v4l2_file_operations vpfe_fops = {.owner = THIS_MODULE,.open = vpfe_open,.release = vpfe_release,.unlocked_ioctl = video_ioctl2,.mmap = vpfe_mmap,.poll = vpfe_poll };

那么是要調用video_ioctl2：

long video_ioctl2(struct file *file,unsigned int cmd, unsigned long arg) {return video_usercopy(file, cmd, arg, __video_do_ioctl);--這個函數最終是要調用__video_do_ioctl，當然他會做其他事，有興趣的可以去了解 }

static long __video_do_ioctl(struct file *file,unsigned int cmd, void *arg) {struct video_device *vfd = video_devdata(file);const struct v4l2_ioctl_ops *ops = vfd->ioctl_ops;----|video_device->ioctl_ops(注意 video_device這幾個函數的調用，要明白他們的作用)bool write_only = false;struct v4l2_ioctl_info default_info;const struct v4l2_ioctl_info *info;void *fh = file->private_data;struct v4l2_fh *vfh = NULL;int dev_debug = vfd->dev_debug;long ret = -ENOTTY;if (ops == NULL) {pr_warn("%s: has no ioctl_ops.\n",video_device_node_name(vfd));return ret;}if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags))vfh = file->private_data;if (v4l2_is_known_ioctl(cmd)) {------------------------檢查命令是否可用info = &v4l2_ioctls[_IOC_NR(cmd)];if (!test_bit(_IOC_NR(cmd), vfd->valid_ioctls) &&!((info->flags & INFO_FL_CTRL) && vfh && vfh->ctrl_handler))goto done;if (vfh && (info->flags & INFO_FL_PRIO)) {ret = v4l2_prio_check(vfd->prio, vfh->prio);if (ret)goto done;}} else {default_info.ioctl = cmd;default_info.flags = 0;default_info.debug = v4l_print_default;info = &default_info;}write_only = _IOC_DIR(cmd) == _IOC_WRITE;if (info->flags & INFO_FL_STD) {-----進入正題，這幾個if會判斷cmd的類型，然后調用不同的函數，這里留個尾巴，詳情見下一節typedef int (*vidioc_op)(struct file *file, void *fh, void *p);const void *p = vfd->ioctl_ops;const vidioc_op *vidioc = p + info->u.offset;/*調用驅動自定義的函數*/ret = (*vidioc)(file, fh, arg);------------調用video_device->ioctl_ops} else if (info->flags & INFO_FL_FUNC) {/*調用架構定義的函數ops，ops最終還是要調用驅動自定義的函數*/ret = info->u.func(ops, file, fh, arg);----調用video_device->ioctl_ops} else if (!ops->vidioc_default) {ret = -ENOTTY;} else {ret = ops->vidioc_default(file, fh,vfh ? v4l2_prio_check(vfd->prio, vfh->prio) >= 0 : 0,cmd, arg);----調用video_device->ioctl_ops->vidioc_default}done:if (dev_debug & (V4L2_DEV_DEBUG_IOCTL | V4L2_DEV_DEBUG_IOCTL_ARG)) {if (!(dev_debug & V4L2_DEV_DEBUG_STREAMING) &&(cmd == VIDIOC_QBUF || cmd == VIDIOC_DQBUF))return ret;v4l_printk_ioctl(video_device_node_name(vfd), cmd);if (ret < 0)pr_cont(": error %ld", ret);if (!(dev_debug & V4L2_DEV_DEBUG_IOCTL_ARG))pr_cont("\n");else if (_IOC_DIR(cmd) == _IOC_NONE)info->debug(arg, write_only);else {pr_cont(": ");info->debug(arg, write_only);}}return ret; }

ioctl命令分類

ioctl命令在文件v4l2-ioctl.c文件中實現，上面分析的函數__video_do_ioctl就在此文件中，在分析這個函數的過程中留了個尾巴，下面來分析一下

從上面的分析過程可以看出最終都是要調用video_device->ioctl_ops，而且調用時還需判斷是INFO_FL_STD還是INFO_FL_FUNC，怎么判斷呢，v4l2-ioctl.c有定義：

IOCTL_INFO_FNC(命令, 實現函數, 打印信息(debug使用), flag)，同樣?
IOCTL_INFO_STD(命令, 實現函數, 打印信息(debug使用), flag)

static struct v4l2_ioctl_info v4l2_ioctls[] = {IOCTL_INFO_FNC(VIDIOC_QUERYCAP, v4l_querycap, v4l_print_querycap, 0),IOCTL_INFO_FNC(VIDIOC_ENUM_FMT, v4l_enum_fmt, v4l_print_fmtdesc, INFO_FL_CLEAR(v4l2_fmtdesc, type)),IOCTL_INFO_FNC(VIDIOC_G_FMT, v4l_g_fmt, v4l_print_format, 0),IOCTL_INFO_FNC(VIDIOC_S_FMT, v4l_s_fmt, v4l_print_format, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_REQBUFS, v4l_reqbufs, v4l_print_requestbuffers, INFO_FL_PRIO | INFO_FL_QUEUE),IOCTL_INFO_FNC(VIDIOC_QUERYBUF, v4l_querybuf, v4l_print_buffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_buffer, length)),IOCTL_INFO_STD(VIDIOC_G_FBUF, vidioc_g_fbuf, v4l_print_framebuffer, 0),IOCTL_INFO_STD(VIDIOC_S_FBUF, vidioc_s_fbuf, v4l_print_framebuffer, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_OVERLAY, v4l_overlay, v4l_print_u32, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_QBUF, v4l_qbuf, v4l_print_buffer, INFO_FL_QUEUE),IOCTL_INFO_STD(VIDIOC_EXPBUF, vidioc_expbuf, v4l_print_exportbuffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_exportbuffer, flags)),IOCTL_INFO_FNC(VIDIOC_DQBUF, v4l_dqbuf, v4l_print_buffer, INFO_FL_QUEUE),IOCTL_INFO_FNC(VIDIOC_STREAMON, v4l_streamon, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),IOCTL_INFO_FNC(VIDIOC_STREAMOFF, v4l_streamoff, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),IOCTL_INFO_FNC(VIDIOC_G_PARM, v4l_g_parm, v4l_print_streamparm, INFO_FL_CLEAR(v4l2_streamparm, type)),IOCTL_INFO_FNC(VIDIOC_S_PARM, v4l_s_parm, v4l_print_streamparm, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_STD, vidioc_g_std, v4l_print_std, 0),IOCTL_INFO_FNC(VIDIOC_S_STD, v4l_s_std, v4l_print_std, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_ENUMSTD, v4l_enumstd, v4l_print_standard, INFO_FL_CLEAR(v4l2_standard, index)),IOCTL_INFO_FNC(VIDIOC_ENUMINPUT, v4l_enuminput, v4l_print_enuminput, INFO_FL_CLEAR(v4l2_input, index)),IOCTL_INFO_FNC(VIDIOC_G_CTRL, v4l_g_ctrl, v4l_print_control, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_control, id)),IOCTL_INFO_FNC(VIDIOC_S_CTRL, v4l_s_ctrl, v4l_print_control, INFO_FL_PRIO | INFO_FL_CTRL),IOCTL_INFO_FNC(VIDIOC_G_TUNER, v4l_g_tuner, v4l_print_tuner, INFO_FL_CLEAR(v4l2_tuner, index)),IOCTL_INFO_FNC(VIDIOC_S_TUNER, v4l_s_tuner, v4l_print_tuner, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_AUDIO, vidioc_g_audio, v4l_print_audio, 0),IOCTL_INFO_STD(VIDIOC_S_AUDIO, vidioc_s_audio, v4l_print_audio, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_QUERYCTRL, v4l_queryctrl, v4l_print_queryctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_queryctrl, id)),IOCTL_INFO_FNC(VIDIOC_QUERYMENU, v4l_querymenu, v4l_print_querymenu, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_querymenu, index)),IOCTL_INFO_STD(VIDIOC_G_INPUT, vidioc_g_input, v4l_print_u32, 0),IOCTL_INFO_FNC(VIDIOC_S_INPUT, v4l_s_input, v4l_print_u32, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_EDID, vidioc_g_edid, v4l_print_edid, 0),IOCTL_INFO_STD(VIDIOC_S_EDID, vidioc_s_edid, v4l_print_edid, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_OUTPUT, vidioc_g_output, v4l_print_u32, 0),IOCTL_INFO_FNC(VIDIOC_S_OUTPUT, v4l_s_output, v4l_print_u32, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_ENUMOUTPUT, v4l_enumoutput, v4l_print_enumoutput, INFO_FL_CLEAR(v4l2_output, index)),IOCTL_INFO_STD(VIDIOC_G_AUDOUT, vidioc_g_audout, v4l_print_audioout, 0),IOCTL_INFO_STD(VIDIOC_S_AUDOUT, vidioc_s_audout, v4l_print_audioout, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_G_MODULATOR, v4l_g_modulator, v4l_print_modulator, INFO_FL_CLEAR(v4l2_modulator, index)),IOCTL_INFO_FNC(VIDIOC_S_MODULATOR, v4l_s_modulator, v4l_print_modulator, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_G_FREQUENCY, v4l_g_frequency, v4l_print_frequency, INFO_FL_CLEAR(v4l2_frequency, tuner)),IOCTL_INFO_FNC(VIDIOC_S_FREQUENCY, v4l_s_frequency, v4l_print_frequency, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_CROPCAP, v4l_cropcap, v4l_print_cropcap, INFO_FL_CLEAR(v4l2_cropcap, type)),IOCTL_INFO_FNC(VIDIOC_G_CROP, v4l_g_crop, v4l_print_crop, INFO_FL_CLEAR(v4l2_crop, type)),IOCTL_INFO_FNC(VIDIOC_S_CROP, v4l_s_crop, v4l_print_crop, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_SELECTION, vidioc_g_selection, v4l_print_selection, INFO_FL_CLEAR(v4l2_selection, r)),IOCTL_INFO_STD(VIDIOC_S_SELECTION, vidioc_s_selection, v4l_print_selection, INFO_FL_PRIO | INFO_FL_CLEAR(v4l2_selection, r)),IOCTL_INFO_STD(VIDIOC_G_JPEGCOMP, vidioc_g_jpegcomp, v4l_print_jpegcompression, 0),IOCTL_INFO_STD(VIDIOC_S_JPEGCOMP, vidioc_s_jpegcomp, v4l_print_jpegcompression, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_QUERYSTD, v4l_querystd, v4l_print_std, 0),IOCTL_INFO_FNC(VIDIOC_TRY_FMT, v4l_try_fmt, v4l_print_format, 0),IOCTL_INFO_STD(VIDIOC_ENUMAUDIO, vidioc_enumaudio, v4l_print_audio, INFO_FL_CLEAR(v4l2_audio, index)),IOCTL_INFO_STD(VIDIOC_ENUMAUDOUT, vidioc_enumaudout, v4l_print_audioout, INFO_FL_CLEAR(v4l2_audioout, index)),IOCTL_INFO_FNC(VIDIOC_G_PRIORITY, v4l_g_priority, v4l_print_u32, 0),IOCTL_INFO_FNC(VIDIOC_S_PRIORITY, v4l_s_priority, v4l_print_u32, INFO_FL_PRIO),IOCTL_INFO_FNC(VIDIOC_G_SLICED_VBI_CAP, v4l_g_sliced_vbi_cap, v4l_print_sliced_vbi_cap, INFO_FL_CLEAR(v4l2_sliced_vbi_cap, type)),IOCTL_INFO_FNC(VIDIOC_LOG_STATUS, v4l_log_status, v4l_print_newline, 0),IOCTL_INFO_FNC(VIDIOC_G_EXT_CTRLS, v4l_g_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL),IOCTL_INFO_FNC(VIDIOC_S_EXT_CTRLS, v4l_s_ext_ctrls, v4l_print_ext_controls, INFO_FL_PRIO | INFO_FL_CTRL),IOCTL_INFO_FNC(VIDIOC_TRY_EXT_CTRLS, v4l_try_ext_ctrls, v4l_print_ext_controls, INFO_FL_CTRL),IOCTL_INFO_STD(VIDIOC_ENUM_FRAMESIZES, vidioc_enum_framesizes, v4l_print_frmsizeenum, INFO_FL_CLEAR(v4l2_frmsizeenum, pixel_format)),IOCTL_INFO_STD(VIDIOC_ENUM_FRAMEINTERVALS, vidioc_enum_frameintervals, v4l_print_frmivalenum, INFO_FL_CLEAR(v4l2_frmivalenum, height)),IOCTL_INFO_STD(VIDIOC_G_ENC_INDEX, vidioc_g_enc_index, v4l_print_enc_idx, 0),IOCTL_INFO_STD(VIDIOC_ENCODER_CMD, vidioc_encoder_cmd, v4l_print_encoder_cmd, INFO_FL_PRIO | INFO_FL_CLEAR(v4l2_encoder_cmd, flags)),IOCTL_INFO_STD(VIDIOC_TRY_ENCODER_CMD, vidioc_try_encoder_cmd, v4l_print_encoder_cmd, INFO_FL_CLEAR(v4l2_encoder_cmd, flags)),IOCTL_INFO_STD(VIDIOC_DECODER_CMD, vidioc_decoder_cmd, v4l_print_decoder_cmd, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_TRY_DECODER_CMD, vidioc_try_decoder_cmd, v4l_print_decoder_cmd, 0),IOCTL_INFO_FNC(VIDIOC_DBG_S_REGISTER, v4l_dbg_s_register, v4l_print_dbg_register, 0),IOCTL_INFO_FNC(VIDIOC_DBG_G_REGISTER, v4l_dbg_g_register, v4l_print_dbg_register, 0),IOCTL_INFO_FNC(VIDIOC_S_HW_FREQ_SEEK, v4l_s_hw_freq_seek, v4l_print_hw_freq_seek, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_S_DV_TIMINGS, vidioc_s_dv_timings, v4l_print_dv_timings, INFO_FL_PRIO),IOCTL_INFO_STD(VIDIOC_G_DV_TIMINGS, vidioc_g_dv_timings, v4l_print_dv_timings, 0),IOCTL_INFO_FNC(VIDIOC_DQEVENT, v4l_dqevent, v4l_print_event, 0),IOCTL_INFO_FNC(VIDIOC_SUBSCRIBE_EVENT, v4l_subscribe_event, v4l_print_event_subscription, 0),IOCTL_INFO_FNC(VIDIOC_UNSUBSCRIBE_EVENT, v4l_unsubscribe_event, v4l_print_event_subscription, 0),IOCTL_INFO_FNC(VIDIOC_CREATE_BUFS, v4l_create_bufs, v4l_print_create_buffers, INFO_FL_PRIO | INFO_FL_QUEUE),IOCTL_INFO_FNC(VIDIOC_PREPARE_BUF, v4l_prepare_buf, v4l_print_buffer, INFO_FL_QUEUE),IOCTL_INFO_STD(VIDIOC_ENUM_DV_TIMINGS, vidioc_enum_dv_timings, v4l_print_enum_dv_timings, 0),IOCTL_INFO_STD(VIDIOC_QUERY_DV_TIMINGS, vidioc_query_dv_timings, v4l_print_dv_timings, 0),IOCTL_INFO_STD(VIDIOC_DV_TIMINGS_CAP, vidioc_dv_timings_cap, v4l_print_dv_timings_cap, INFO_FL_CLEAR(v4l2_dv_timings_cap, type)),IOCTL_INFO_FNC(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),IOCTL_INFO_FNC(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),IOCTL_INFO_FNC(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)), };

上面的分析中一直說到video_device->ioctl_ops，那么ioctl_ops有多少函數呢。。很多見下：?
算了還是不粘貼了自己去代碼中看吧，這里只粘一點：

struct v4l2_ioctl_ops {/* ioctl callbacks *//* VIDIOC_QUERYCAP handler */int (*vidioc_querycap)(struct file *file, void *fh, struct v4l2_capability *cap);/* VIDIOC_ENUM_FMT handlers */int (*vidioc_enum_fmt_vid_cap) (struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_vid_overlay) (struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_vid_out) (struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_vid_cap_mplane)(struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_vid_out_mplane)(struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_sdr_cap) (struct file *file, void *fh,struct v4l2_fmtdesc *f);int (*vidioc_enum_fmt_sdr_out) (struct file *file, void *fh,struct v4l2_fmtdesc *f);。。。/* DV Timings IOCTLs */int (*vidioc_s_dv_timings) (struct file *file, void *fh,struct v4l2_dv_timings *timings);int (*vidioc_g_dv_timings) (struct file *file, void *fh,struct v4l2_dv_timings *timings);int (*vidioc_query_dv_timings) (struct file *file, void *fh,struct v4l2_dv_timings *timings);int (*vidioc_enum_dv_timings) (struct file *file, void *fh,struct v4l2_enum_dv_timings *timings);int (*vidioc_dv_timings_cap) (struct file *file, void *fh,struct v4l2_dv_timings_cap *cap);int (*vidioc_g_edid) (struct file *file, void *fh, struct v4l2_edid *edid);int (*vidioc_s_edid) (struct file *file, void *fh, struct v4l2_edid *edid);int (*vidioc_subscribe_event) (struct v4l2_fh *fh,const struct v4l2_event_subscription *sub);int (*vidioc_unsubscribe_event)(struct v4l2_fh *fh,const struct v4l2_event_subscription *sub);/* For other private ioctls */long (*vidioc_default) (struct file *file, void *fh,bool valid_prio, unsigned int cmd, void *arg); };

ioctl調用總圖

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