Hi Hans,
Hans Verkuil wrote:
[clip]
>>> diff --git a/drivers/media/video/v4l2-fh.c
>>> b/drivers/media/video/v4l2-fh.c
>>> index 8635011..c6aef84 100644
>>> --- a/drivers/media/video/v4l2-fh.c
>>> +++ b/drivers/media/video/v4l2-fh.c
>>> @@ -93,10 +93,8 @@ void v4l2_fh_exit(struct v4l2_fh *fh)
>>> {
>>> if (fh->vdev == NULL)
>>> return;
>>> -
>>> - fh->vdev = NULL;
>>> -
>>> v4l2_event_free(fh);
>>> + fh->vdev = NULL;
>>
>> This looks like a bugfix.
>
> But it isn't :-)
>
> v4l2_event_free didn't use fh->vdev in the past, but now it does so the
> order had to be swapped.
Ok.
>>
>>> }
>>> EXPORT_SYMBOL_GPL(v4l2_fh_exit);
>>>
>>> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
>>> index 92d2fdd..f7238c1 100644
>>> --- a/include/linux/videodev2.h
>>> +++ b/include/linux/videodev2.h
>>> @@ -1787,6 +1787,7 @@ struct v4l2_streamparm {
>>> #define V4L2_EVENT_ALL 0
>>> #define V4L2_EVENT_VSYNC 1
>>> #define V4L2_EVENT_EOS 2
>>> +#define V4L2_EVENT_CTRL_CH_VALUE 3
>>> #define V4L2_EVENT_PRIVATE_START 0x08000000
>>>
>>> /* Payload for V4L2_EVENT_VSYNC */
>>> @@ -1795,21 +1796,33 @@ struct v4l2_event_vsync {
>>> __u8 field;
>>> } __attribute__ ((packed));
>>>
>>> +/* Payload for V4L2_EVENT_CTRL_CH_VALUE */
>>> +struct v4l2_event_ctrl_ch_value {
>>> + __u32 type;
>>
>> type is enum v4l2_ctrl_type in struct v4l2_ctrl and struct v4l2_queryctrl.
>
> Yes, but enum's are frowned upon these days in the public API.
Agreed.
>>
>>> + union {
>>> + __s32 value;
>>> + __s64 value64;
>>> + };
>>> +} __attribute__ ((packed));
>>> +
>>> struct v4l2_event {
>>> __u32 type;
>>> union {
>>> struct v4l2_event_vsync vsync;
>>> + struct v4l2_event_ctrl_ch_value ctrl_ch_value;
>>> __u8 data[64];
>>> } u;
>>> __u32 pending;
>>> __u32 sequence;
>>> struct timespec timestamp;
>>> - __u32 reserved[9];
>>> + __u32 id;
>>
>> id is valid only for control related events. Shouldn't it be part of the
>> control related structures instead, or another union for control related
>> event types? E.g.
>>
>> struct {
>> enum v4l2_ctrl_type id;
>> union {
>> struct v4l2_event_ctrl_ch_value ch_value;
>> };
>> } ctrl;
>
> The problem with making this dependent of the type is that the core event
> code would have to have a switch on the event type when it comes to
> matching identifiers. By making it a core field it doesn't have to do
> this. Also, this makes it available for use by private events as well.
>
> It is important to keep the send-event core code as fast as possible since
> it can be called from interrupt context.
>
> So this is by design.
I understand your point, and agree with it. There would be a few places
in the v4l2-event.c that one would have to know if the event is
control-related or not.
As the id field is handled in the v4l2-event.c the way it is, it must be
zero when the event is not a control-related one. This makes it
impossible to use it for other purposes, at least for now.
What about renaming the field to ctrl_id? Or do you think we could have
other use for the field outside the scope of the control-related events?
The benefit of the current name is still that it does not suggest
anything on the implementation.
Cheers,
--
Sakari Ailus
sakari.ai...@maxwell.research.nokia.com
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