[libcamera-devel] [PATCH v2 1/2] libcamera: v4l2_videodevice: Add a dequeue timer

[Naushir Patuck]

Hi Kieran,


On Thu, 24 Mar 2022 at 12:53, Kieran Bingham <
kieran.bingham at ideasonboard.com> wrote:

> Hi Naush,
>
> Thanks - this looks pretty good to me.
> But Doxygen is generating warnings on this:
>
> [7/7] Generating doxygen with a custom command
> /home/kbingham/iob/libcamera/libcamera/include/libcamera/internal/v4l2_videodevice.h:222:
> warning: Member dequeueTimeout (variable) of class
> libcamera::V4L2VideoDevice is not documented.
> /home/kbingham/iob/libcamera/libcamera/src/libcamera/v4l2_videodevice.cpp:1864:
> warning: unable to resolve reference to 'V4L2VideoDevice::dequeueTimeout'
> for \ref command
>

Sorry, I missed those!  Now fixed.


>
> Also it's missing a unit test. Fortunately I was curious enough to see
> how it works, so I've just written the test, and I'll post it in reply
> to this.
>

Thanks! I'll add this to the next revision of the patch.

Regards,
Naush


>
> --
> Kieran
>
>
> Quoting Naushir Patuck via libcamera-devel (2022-03-24 09:34:08)
> > Add a timer that gets reset on every buffer dequeue event. If the timeout
> > expires, optionally call a slot in the pipeline handler to handle this
> > condition. This may be useful in detecting and handling stalls in either
> the
> > hardware or device driver.
> >
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > ---
> >  include/libcamera/internal/v4l2_videodevice.h | 10 ++++
> >  src/libcamera/v4l2_videodevice.cpp            | 49 +++++++++++++++++++
> >  2 files changed, 59 insertions(+)
> >
> > diff --git a/include/libcamera/internal/v4l2_videodevice.h
> b/include/libcamera/internal/v4l2_videodevice.h
> > index 2d2ccc477c91..c34cc6585612 100644
> > --- a/include/libcamera/internal/v4l2_videodevice.h
> > +++ b/include/libcamera/internal/v4l2_videodevice.h
> > @@ -9,6 +9,7 @@
> >
> >  #include <array>
> >  #include <atomic>
> > +#include <chrono>
> >  #include <memory>
> >  #include <optional>
> >  #include <stdint.h>
> > @@ -20,6 +21,7 @@
> >  #include <libcamera/base/class.h>
> >  #include <libcamera/base/log.h>
> >  #include <libcamera/base/signal.h>
> > +#include <libcamera/base/timer.h>
> >  #include <libcamera/base/unique_fd.h>
> >
> >  #include <libcamera/color_space.h>
> > @@ -216,6 +218,9 @@ public:
> >         int streamOn();
> >         int streamOff();
> >
> > +       void setDequeueTimeout(std::chrono::milliseconds msec);
> > +       Signal<> dequeueTimeout;
> > +
> >         static std::unique_ptr<V4L2VideoDevice>
> >         fromEntityName(const MediaDevice *media, const std::string
> &entity);
> >
> > @@ -246,6 +251,8 @@ private:
> >         void bufferAvailable();
> >         FrameBuffer *dequeueBuffer();
> >
> > +       void watchdogExpired();
> > +
> >         V4L2Capability caps_;
> >         V4L2DeviceFormat format_;
> >         const PixelFormatInfo *formatInfo_;
> > @@ -259,6 +266,9 @@ private:
> >         EventNotifier *fdBufferNotifier_;
> >
> >         bool streaming_;
> > +
> > +       Timer watchdog_;
> > +       std::chrono::milliseconds watchdogDuration_;
> >  };
> >
> >  class V4L2M2MDevice
> > diff --git a/src/libcamera/v4l2_videodevice.cpp
> b/src/libcamera/v4l2_videodevice.cpp
> > index 5f36ee20710d..29225f3058b0 100644
> > --- a/src/libcamera/v4l2_videodevice.cpp
> > +++ b/src/libcamera/v4l2_videodevice.cpp
> > @@ -526,6 +526,7 @@ V4L2VideoDevice::V4L2VideoDevice(const std::string
> &deviceNode)
> >  V4L2VideoDevice::V4L2VideoDevice(const MediaEntity *entity)
> >         : V4L2VideoDevice(entity->deviceNode())
> >  {
> > +       watchdog_.timeout.connect(this,
> &V4L2VideoDevice::watchdogExpired);
> >  }
> >
> >  V4L2VideoDevice::~V4L2VideoDevice()
> > @@ -1695,6 +1696,9 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
> >                 return nullptr;
> >         }
> >
> > +       if (watchdogDuration_.count())
> > +               watchdog_.start(watchdogDuration_);
> > +
> >         cache_->put(buf.index);
> >
> >         FrameBuffer *buffer = it->second;
> > @@ -1797,6 +1801,8 @@ int V4L2VideoDevice::streamOn()
> >         }
> >
> >         streaming_ = true;
> > +       if (watchdogDuration_.count())
> > +               watchdog_.start(watchdogDuration_);
> >
> >         return 0;
> >  }
> > @@ -1821,6 +1827,9 @@ int V4L2VideoDevice::streamOff()
> >         if (!streaming_ && queuedBuffers_.empty())
> >                 return 0;
> >
> > +       if (watchdogDuration_.count())
> > +               watchdog_.stop();
> > +
> >         ret = ioctl(VIDIOC_STREAMOFF, &bufferType_);
> >         if (ret < 0) {
> >                 LOG(V4L2, Error)
> > @@ -1843,6 +1852,46 @@ int V4L2VideoDevice::streamOff()
> >         return 0;
> >  }
> >
> > +/**
> > + * \brief Set the dequeue timeout value
> > + * \param[in] msec The timeout value to be used
> > + *
> > + * Sets a timeout value, given by \a msec, that will be used by a
> watchdog timer
> > + * to ensure buffer dequeue events are periodically occurring when the
> device is
> > + * streaming. The watchdog timer is only active when the device is
> streaming, so
> > + * it is not necessary to disable it when the device stops streaming.
> The timeout
> > + * value can be safely updated at any time.
> > + *
> > + * If the timer expires, the \ref V4L2VideoDevice::dequeueTimeout
> signal is
> > + * emitted. This can typically be used by pipeline handlers to be
> notified of
> > + * stalled devices.
> > + *
> > + * Set \a msec to 0 to disable the watchdog timer.
> > + */
> > +void V4L2VideoDevice::setDequeueTimeout(std::chrono::milliseconds msec)
> > +{
> > +       watchdogDuration_ = msec;
> > +
> > +       watchdog_.stop();
> > +       if (watchdogDuration_.count() && streaming_)
> > +               watchdog_.start(msec);
> > +}
> > +
> > +/**
> > + * \brief Slot to handle an expired dequeue timer.
> > + *
> > + * When this slot is called, the time between successive dequeue events
> is over
> > + * the required timeout. Emit the \ref V4L2VideoDevice::dequeueTimeout
> signal.
> > + */
> > +void V4L2VideoDevice::watchdogExpired()
> > +{
> > +       LOG(V4L2, Warning)
> > +               << "Dequeue timer of " << watchdogDuration_.count()
> > +               << " ms has expired!";
> > +
> > +       dequeueTimeout.emit();
> > +}
> > +
> >  /**
> >   * \brief Create a new video device instance from \a entity in media
> device
> >   * \a media
> > --
> > 2.25.1
> >
>
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