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SubjectRe: [PATCH RFC 0/3] meida: uvcvideo: reimplement privacy gpio as a separate subdevice
Hi Yunke

Thank you very much for the patchset :)

On Wed, 11 Jan 2023 at 09:52, Yunke Cao <yunkec@chromium.org> wrote:
>
> privacy_gpio in uvc were added as V4L2_CID_PRIVACY in uvc video node in
> https://lore.kernel.org/all/20201223133528.55014-1-ribalda@chromium.org/
>
> Userspace applications often require to constantly poll privacy control.
> Currently, polling privacy control requires keeping the video node open,
> which prevents the camera from autosuspending.
>
> This patchset adds a separate v4l2 subdevice. Userspace access the gpio
> via V4L2_CID_PRIVACY in the new subdevice. Applications can poll the
> privacy control status without opening the video node and activate the
> camera.
>
> The non-gpio V4L2_CID_PRIVACY in uvc is not affected.

Since this is a RFC, lets focus on the idea and not on the code itself.

- I am missing a reference to the subdevice from the media device. How
will a user figure out that /dev/v4l-subdev0 is the privacy gpio of
/dev/media0 and not /dev/media1?. Thake a look to the "ancillary
links"
- We have already exposed the control as part of the main video
device, that means that we need to keep that API. The control on
/dev/v4l-subdev0 should "mirror" the control on /dev/video0
- There is no need to v4l2_ctrl_fill_event(), if you modify the
control with a set controll function, the media controller should take
care of everything

@Sakari Ailus @Hans Verkuil : Assuming a correct implementation, how
would you feel about exposing a privacy gpio as a subdevice?


Thanks!!!


>
> Suggested-by: Ricardo Ribalda <ribalda@chromium.org>
> Signed-off-by: Yunke Cao <yunkec@chromium.org>
> ---
> Yunke Cao (3):
> media: v4l2-ctrls: Expose v4l2_ctrl_fill_event()
> media: uvcvideo: remove entity privacy control in the uvc video node
> media: uvcvideo: reimplement privacy GPIO as a separate subdevice
>
> drivers/media/usb/uvc/uvc_ctrl.c | 17 -------
> drivers/media/usb/uvc/uvc_driver.c | 44 ++----------------
> drivers/media/usb/uvc/uvc_entity.c | 76 +++++++++++++++++++++++++++++++
> drivers/media/usb/uvc/uvcvideo.h | 19 +++++---
> drivers/media/v4l2-core/v4l2-ctrls-core.c | 9 ++--
> include/media/v4l2-ctrls.h | 12 +++++
> 6 files changed, 111 insertions(+), 66 deletions(-)
> ---
> base-commit: 7dd4b804e08041ff56c88bdd8da742d14b17ed25
> change-id: 20230111-uvc_privacy_subdev-1e7a167e86eb
>
> Best regards,
> --
> Yunke Cao <yunkec@chromium.org>



--
Ricardo Ribalda

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