[libcamera-devel] [PATCH v3 1/3] libcamera: v4l2_videodevice: Add a dequeue timer

[Naushir Patuck]

Hi Umang,

On Tue, 5 Apr 2022 at 14:56, Umang Jain <umang.jain at ideasonboard.com> wrote:

> Hi Naushir,
>
> Just a drive-by comment,
>
> On 3/29/22 16:59, Naushir Patuck via libcamera-devel wrote:
> > 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            | 54 +++++++++++++++++++
> >   2 files changed, 64 insertions(+)
> >
> > diff --git a/include/libcamera/internal/v4l2_videodevice.h
> b/include/libcamera/internal/v4l2_videodevice.h
> > index cfeae7bd6c52..2a9ba1fe5c71 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>
> > @@ -217,6 +219,9 @@ 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);
> >
> > @@ -253,6 +258,8 @@ private:
> >       void bufferAvailable();
> >       FrameBuffer *dequeueBuffer();
> >
> > +     void watchdogExpired();
> > +
> >       V4L2Capability caps_;
> >       V4L2DeviceFormat format_;
> >       const PixelFormatInfo *formatInfo_;
> > @@ -266,6 +273,9 @@ private:
> >       EventNotifier *fdBufferNotifier_;
> >
> >       State state_;
> > +
> > +     Timer watchdog_;
> > +     std::chrono::milliseconds watchdogDuration_;
>
>
> Any particular reason this is std::chrono::miiliseconds instead of using
> utils::Duration ?
>

In the previous revision, I did use the utils::Duration type for this
variable.
However, Laurent suggested that we might want to avoid that as he intends to
move utils::Duration to the "public" API, and would not be available to use
in this case.  So I switched to std::chrono::milliseconds.

Regards,
Naush


>
> >   };
> >
> >   class V4L2M2MDevice
> > diff --git a/src/libcamera/v4l2_videodevice.cpp
> b/src/libcamera/v4l2_videodevice.cpp
> > index 009f6d55610f..22191cb9de4d 100644
> > --- a/src/libcamera/v4l2_videodevice.cpp
> > +++ b/src/libcamera/v4l2_videodevice.cpp
> > @@ -539,6 +539,7 @@ V4L2VideoDevice::V4L2VideoDevice(const std::string
> &deviceNode)
> >   V4L2VideoDevice::V4L2VideoDevice(const MediaEntity *entity)
> >       : V4L2VideoDevice(entity->deviceNode())
> >   {
> > +     watchdog_.timeout.connect(this, &V4L2VideoDevice::watchdogExpired);
> >   }
> >
> >   V4L2VideoDevice::~V4L2VideoDevice()
> > @@ -1723,6 +1724,9 @@ FrameBuffer *V4L2VideoDevice::dequeueBuffer()
> >               return nullptr;
> >       }
> >
> > +     if (watchdogDuration_.count())
> > +             watchdog_.start(watchdogDuration_);
> > +
> >       cache_->put(buf.index);
> >
> >       FrameBuffer *buffer = it->second;
> > @@ -1825,6 +1829,8 @@ int V4L2VideoDevice::streamOn()
> >       }
> >
> >       state_ = State::Streaming;
> > +     if (watchdogDuration_.count())
> > +             watchdog_.start(watchdogDuration_);
> >
> >       return 0;
> >   }
> > @@ -1849,6 +1855,9 @@ int V4L2VideoDevice::streamOff()
> >       if (state_ != State::Streaming && queuedBuffers_.empty())
> >               return 0;
> >
> > +     if (watchdogDuration_.count())
> > +             watchdog_.stop();
> > +
> >       ret = ioctl(VIDIOC_STREAMOFF, &bufferType_);
> >       if (ret < 0) {
> >               LOG(V4L2, Error)
> > @@ -1876,6 +1885,51 @@ 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)
>
>
> Same here as well. I guess you take in a `utils::Duration msec` and
> assign to watchdogDuration_ below (given you have utils::Duration
> watchdogDuration_ too).
>
> > +{
> > +     watchdogDuration_ = msec;
> > +
> > +     watchdog_.stop();
> > +     if (watchdogDuration_.count() && state_ == State::Streaming)
> > +             watchdog_.start(msec);
> > +}
> > +
> > +/**
> > + * \var V4L2VideoDevice::dequeueTimeout
> > + * \brief A Signal emitted when the dequeue watchdog timer expires
> > + */
> > +
> > +/**
> > + * \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
>
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