On 1/28/19 10:21 AM, Sakari Ailus wrote:
> Hi Hans,
>
> Thanks for the patch.
>
> On Sat, Jan 26, 2019 at 12:06:19PM +0100, Hans Verkuil wrote:
>> This patch adds an extended version of VIDIOC_DQEVENT that:
>>
>> 1) is Y2038 safe by using a __u64 for the timestamp
>> 2) needs no compat32 conversion code
>> 3) is able to handle control events from 64-bit control types
>> by changing the type of the minimum, maximum, step and default_value
>> field to __u64
>>
>> All drivers and frameworks will be using this, and v4l2-ioctl.c would be the
>> only place where the old event ioctl and structs are used.
>>
>> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
>> ---
>> Please let me know if there are additional requests for such a new ioctl.
>>
>> Note that I am using number 104 for the ioctl, but perhaps it would be better to
>> use an unused ioctl number like 1 or 3. There are quite a few holes in the
>> ioctl numbers. We currently have only 82 ioctls, yet are up to ioctl number 103.
>> ---
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 9a920f071ff9..969e775b8c25 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -2303,6 +2303,37 @@ struct v4l2_event {
>> __u32 reserved[8];
>> };
>>
>> +struct v4l2_event_ext_ctrl {
>> + __u32 changes;
>> + __u32 type;
>> + union {
>> + __s32 value;
>> + __s64 value64;
>> + };
>> + __s64 minimum;
>> + __s64 maximum;
>> + __s64 step;
>> + __s64 default_value;
>> + __u32 flags;
>> +};
>> +
>> +struct v4l2_ext_event {
>> + __u32 type;
>> + __u32 id;
>> + union {
>> + struct v4l2_event_vsync vsync;
>> + struct v4l2_event_ext_ctrl ctrl;
>> + struct v4l2_event_frame_sync frame_sync;
>> + struct v4l2_event_src_change src_change;
>> + struct v4l2_event_motion_det motion_det;
>> + __u8 data[64];
>> + } u;
>
> If I'd change something in the event IOCTL, I'd probably put the reserved
> fields here. That'd allow later taking some for the use of the event data
> if needed.
Good point, I'll do that.
> I might also increase the size of the event data. 64 bytes is not that
> much. But you indeed end up copying it around all the time... So it's a
> trade-off.
I decided to leave this alone. I think by putting the reserved array after
the union (nice idea) we allow for such future extension should it be
necessary.
>
>> + __u64 timestamp;
>> + __u32 pending;
>> + __u32 sequence;
>> + __u32 reserved[8];
>> +};
>> +
>> #define V4L2_EVENT_SUB_FL_SEND_INITIAL (1 << 0)
>> #define V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK (1 << 1)
>>
>> @@ -2475,6 +2506,7 @@ struct v4l2_create_buffers {
>> #define VIDIOC_DBG_G_CHIP_INFO _IOWR('V', 102, struct v4l2_dbg_chip_info)
>>
>> #define VIDIOC_QUERY_EXT_CTRL _IOWR('V', 103, struct v4l2_query_ext_ctrl)
>> +#define VIDIOC_DQEXTEVENT _IOR('V', 104, struct v4l2_ext_event)
>
> How do you plan to name the new buffer handling IOCTLs? I.e. with or
> without underscores around "EXT"?
It's a good question. In my old patch I named them VIDIOC_EXT_QBUF etc. See:
https://git.linuxtv.org/hverkuil/media_tree.git/commit/?h=v4l2-buffer&id=a95549df06d9900f3559afdbb9da06bd4b22d1f3
So I think I should probably rename this to VIDIOC_EXT_DQEVENT.
Alternatively, perhaps we should ditch the _ext_ usage and instead use a
version suffix: VIDIOC_DQEVENT_V2.
The problem with EXT is that if you want to make a newer version of such a
control, you can't just name it EXT_EXT, that would be silly. But naming it
_V3 would be fine.
Frankly, the extended control ioctls have that problem, also due to awful
64 bit alignment issues. It would be really nice to have _V3 versions of
those ioctls that do not require compat32 code.
Feedback on this would be very welcome!
Regards,
Hans
>
>>
>> /* Reminder: when adding new ioctls please add support for them to
>> drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
>
