视频驱动V4L2子系统驱动架构 - ioctl
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#文章系列
视频驱动V4L2子系统驱动架构 - 驱动框架
视频驱动V4L2子系统驱动架构 - ioctl
基于linux4.6.3,最后会附上一张ioctl调用总图，分析代码还是要用图来说明，这样更清晰一点，我就是这么分析的，不过平时分析的图很随便，而且很大，所以就不能在这里呈现，我在这里会贴出一个简略图
#ioctl详解
进入ioctl都是从cdev->ops->ioctl进入的，一般的驱动cdev都是驱动自己初始化的，在v4l2架构中，cdev都已经初始化完成，不需要驱动开发者来初始化，下面是v4l2的cdev->ops结构体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有两个，一个unlocked_ioctl，另一个是compat_ioctl 兼容性的，其中的区别这里不多说，我们来看函数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);--正常进入函数|video_device->fops
if (lock)
mutex_unlock(lock);
} else
ret = -ENOTTY;
return ret;
}
从上可以看到要调用vdev->fops->unlocked_ioctl(filp, cmd, arg);具体驱动实现不同，以davinci平台为例来介绍，在vpfe_capture.c文件中，初始化过程中有
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
};
那么是要调用video_ioctl2：
long video_ioctl2(struct file *file,
unsigned int cmd, unsigned long arg)
{
return video_usercopy(file, cmd, arg, __video_do_ioctl);--这个函数最终是要调用__video_do_ioctl，当然他会做其他事，有兴趣的可以去了解
}
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这几个函数的调用，要明白他们的作用)
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)) {------------------------检查命令是否可用
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) {-----进入正题，这几个if会判断cmd的类型，然后调用不同的函数，这里留个尾巴，详情见下一节
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;
/*调用驱动自定义的函数*/
ret = (*vidioc)(file, fh, arg);------------调用video_device->ioctl_ops
} else if (info->flags & INFO_FL_FUNC) {
/*调用架构定义的函数ops，ops最终还是要调用驱动自定义的函数*/
ret = info->u.func(ops, file, fh, arg);----调用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);----调用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命令分类
ioctl命令在文件v4l2-ioctl.c文件中实现，上面分析的函数__video_do_ioctl就在此文件中，在分析这个函数的过程中留了个尾巴，下面来分析一下
从上面的分析过程可以看出最终都是要调用video_device->ioctl_ops，而且调用时还需判断是INFO_FL_STD还是INFO_FL_FUNC，怎么判断呢，v4l2-ioctl.c有定义：
IOCTL_INFO_FNC(命令, 实现函数, 打印信息(debug使用), flag)，同样
IOCTL_INFO_STD(命令, 实现函数, 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)),
};
上面的分析中一直说到video_device->ioctl_ops，那么ioctl_ops有多少函数呢。。很多见下：
算了还是不粘贴了自己去代码中看吧，这里只粘一点：
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调用总图
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