[PATCH] libcamera: v4l2: Support changing poller thread for V4L2VideoDevice

[Kieran Bingham]

Quoting Harvey Yang (2024-10-16 14:46:33)
> From: Han-Lin Chen <hanlinchen at chromium.org>
> 

Could we get something more detailed in here?

What use case does this support ? Are there any restrictions on how/when
you move the thread? What's the default thread used to poll - and why
isn't this sufficient?

This seems like the sort of thing that deserves a test in
test/v4l2_videodevice.cpp to make sure the devices still operate after
the poll thread has been moved ?


> Signed-off-by: Han-Lin Chen <hanlinchen at chromium.org>
> Co-developed-by: Yudhistira Erlandinata <yerlandinata at chromium.org>
> Signed-off-by: Yudhistira Erlandinata <yerlandinata at chromium.org>
> Co-developed-by: Harvey Yang <chenghaoyang at chromium.org>
> Signed-off-by: Harvey Yang <chenghaoyang at chromium.org>
> ---
>  include/libcamera/internal/v4l2_videodevice.h |  2 ++
>  src/libcamera/v4l2_videodevice.cpp            | 13 +++++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> index f021c2a01..f8d017b01 100644
> --- a/include/libcamera/internal/v4l2_videodevice.h
> +++ b/include/libcamera/internal/v4l2_videodevice.h
> @@ -232,6 +232,8 @@ public:
>  
>         V4L2PixelFormat toV4L2PixelFormat(const PixelFormat &pixelFormat) const;
>  
> +       void changePollerThread(Thread *thread);
> +
>  protected:
>         std::string logPrefix() const override;
>  
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index 14eba0561..fc6b88ec1 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -2120,6 +2120,19 @@ V4L2PixelFormat V4L2VideoDevice::toV4L2PixelFormat(const PixelFormat &pixelForma
>         return {};
>  }
>  
> +/**
> + * \brief Move the event notifier and timer to \a thread
> + * \param[in] thread The thread to poll on
> + */
> +void V4L2VideoDevice::changePollerThread(Thread *thread)
> +{
> +       if (!isOpen())
> +               return;
> +
> +       fdBufferNotifier_->moveToThread(thread);
> +       watchdog_.moveToThread(thread);
> +}
> +
>  /**
>   * \class V4L2M2MDevice
>   * \brief Memory-to-Memory video device
> -- 
> 2.47.0.rc1.288.g06298d1525-goog
>