Re: [PATCH RFC 5/5] media: imx219: Add status polling using .detect()

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Dave,

Thank you for the review.

On Thu, Oct 01, 2026 at 16:58, Dave Stevenson <dave.stevenson@raspberrypi.com> wrote:

> Hi Mattij
>
> On Thu, 1 Oct 2026 at 13:55, Mattijs Korpershoek
> <mkorpershoek@kernel.org> wrote:
>>
>> Userspace needs to be notified when a sensor connection status
>> changes (e.g. disconnected at boot, then later reconnected) so it can
>> react accordingly.
>>
>> Add periodic polling using a delayed work that calls .detect() every
>> 2s and sends a KOBJ_CHANGE uevent with HOTPLUG=1 on status changes.
>> This mirrors the approach used by DRM connectors in output_poll_execute().
>
> AIUI DRM polls from within the framework (drm_probe_helper.c), not by
> a workqueue in the individual drivers.

Yes, that's my understanding as well.

>
> Admittedly V4L2 doesn't currently have a totally obvious place to
> setup this, but it would be far less effort to have the polling
> framework within the core code rather than driver.
> Possibly initialised in __v4l2_async_register_subdev_sensor() based on
> whether .detect is set, and cleaned up in
> v4l2_async_unregister_subdev, with the workqueue calling .detect and
> generating the udev event based on the return value? I think that's
> feasible.

I agree with you that the polling should not be done in every sensor
driver.
I did it this way to illustrate how this would all be tied together in a
simple exemple (one sensor driver).

If we move forward with this series, I'll rework this to
be done in a generic way.

Mattijs

>
>   Dave
>