[libcamera-devel] [PATCH 1/2] libcamera: request: Add support for error flags

[Kieran Bingham]

Quoting Jacopo Mondi (2022-07-19 16:40:12)
> Hi Kieran
> 
> On Tue, Jul 19, 2022 at 11:31:43AM +0100, Kieran Bingham via libcamera-devel wrote:
> > From: Paul Elder <paul.elder at ideasonboard.com>
> >
> > Add error flags to the Request to indicate non-fatal errors.
> >
> > Applications should check the error() state of the Request to determine
> > if any fault occured while processing the request.
> >
> > Initially, a single error flag ControlError is added to allow a pipeline
> > handler to report a failure to set controls on a hardware device while
> > processing the request.
> >
> > ControlErrors occur when a Request was asked to set a control and the
> > pipeline handler attempted to do so, but it was rejected by the kernel.
> >
> > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > ---
> >  include/libcamera/internal/request.h |  3 +++
> >  include/libcamera/request.h          |  9 +++++++
> >  src/libcamera/request.cpp            | 36 ++++++++++++++++++++++++++++
> >  3 files changed, 48 insertions(+)
> >
> > diff --git a/include/libcamera/internal/request.h b/include/libcamera/internal/request.h
> > index 9dadd6c60361..8e592272cfae 100644
> > --- a/include/libcamera/internal/request.h
> > +++ b/include/libcamera/internal/request.h
> > @@ -38,6 +38,7 @@ public:
> >       void complete();
> >       void cancel();
> >       void reuse();
> > +     void setErrorFlags(ErrorFlags flags);
> >
> >       void prepare(std::chrono::milliseconds timeout = 0ms);
> >       Signal<> prepared;
> > @@ -59,6 +60,8 @@ private:
> >       std::unordered_set<FrameBuffer *> pending_;
> >       std::map<FrameBuffer *, std::unique_ptr<EventNotifier>> notifiers_;
> >       std::unique_ptr<Timer> timer_;
> > +
> > +     ErrorFlags error_;
> >  };
> >
> >  } /* namespace libcamera */
> > diff --git a/include/libcamera/request.h b/include/libcamera/request.h
> > index dffde1536cad..992629e11aa4 100644
> > --- a/include/libcamera/request.h
> > +++ b/include/libcamera/request.h
> > @@ -15,6 +15,7 @@
> >  #include <unordered_set>
> >
> >  #include <libcamera/base/class.h>
> > +#include <libcamera/base/flags.h>
> >  #include <libcamera/base/signal.h>
> >
> >  #include <libcamera/controls.h>
> > @@ -43,6 +44,13 @@ public:
> >               ReuseBuffers = (1 << 0),
> >       };
> >
> > +     enum ErrorFlag {
> > +             NoError = 0,
> > +             ControlError = (1 << 0),
> > +     };
> > +
> > +     using ErrorFlags = Flags<ErrorFlag>;
> > +
> >       using BufferMap = std::map<const Stream *, FrameBuffer *>;
> >
> >       Request(Camera *camera, uint64_t cookie = 0);
> > @@ -60,6 +68,7 @@ public:
> >       uint32_t sequence() const;
> >       uint64_t cookie() const { return cookie_; }
> >       Status status() const { return status_; }
> > +     ErrorFlags error() const;
> >
> >       bool hasPendingBuffers() const;
> >
> > diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp
> > index 07613cb33709..d585ef0b0ae4 100644
> > --- a/src/libcamera/request.cpp
> > +++ b/src/libcamera/request.cpp
> > @@ -162,6 +162,7 @@ void Request::Private::cancel()
> >   */
> >  void Request::Private::reuse()
> >  {
> > +     error_ = Request::NoError;
> >       sequence_ = 0;
> >       cancelled_ = false;
> >       prepared_ = false;
> > @@ -284,6 +285,11 @@ void Request::Private::notifierActivated(FrameBuffer *buffer)
> >       emitPrepareCompleted();
> >  }
> >
> > +void Request::Private::setErrorFlags(ErrorFlags flags)
> > +{
> > +     error_ |= flags;
> > +}
> > +
> >  void Request::Private::timeout()
> >  {
> >       /* A timeout can only happen if there are fences not yet signalled. */
> > @@ -318,6 +324,22 @@ void Request::Private::timeout()
> >   * Reuse the buffers that were previously added by addBuffer()
> >   */
> >
> > +/**
> > + * \enum Request::ErrorFlag
> > + * Flags to report non-fatal errors
> 
> I'm afraid the documentation should likely be expanded a bit :)

Well this was supposed to be marked RFC ;-) so sure.
 
> In particular, what does it mean for application an error is non-fatal ?
> That the request contains valid data ? That the request does not contain
> valid data but the device is operating and new requests can be queued ?
> 
> > + * \var Request::NoError
> > + * No error
> 
> Do we need a NoError ?

Yes, we need to be able to initialise to 'No Error'.
See Request::Private::reuse() above.

(You can't set error_ = 0, with Flags<>);

> 
> Isn't testing with:
> 
>         if (request->error())

Yes, that's also sufficient. These two are equivalent:

	if (request->error())
	if (request->error() != Request::NoError)



> enough ?
> 
> > + * \var Request::ControlError
> > + * Control Error. At least on control was not able to be applied to the device.
> 
> s/on control/one control
> 
> > + * The application should compare the metadata to the requested control values
> > + * to check which controls weren't applied.
> > + */
> > +
> > +/**
> > + * \typedef Request::ErrorFlags
> > + * The error state of the request.
> > + */
> > +
> >  /**
> >   * \typedef Request::BufferMap
> >   * \brief A map of Stream to FrameBuffer pointers
> > @@ -560,6 +582,20 @@ uint32_t Request::sequence() const
> >   * \return The request completion status
> >   */
> >
> > +/**
> > + * \brief Retrieve the error flags
> > + *
> > + * The request could complete with non-fatal error. The completion status will
> > + * indicate success. This function returns the non-fatal errors that the
> > + * request completed with
> > + *
> 
> Here as well I think a better definition of success and what fatal
> means is required. Linking to the flags enum documentation, when
> expanded, might be enough

Linking to the detail of the enums is certainly a good addition.


> 
> > + * \return Flags of non-fatal errors that the request completed with
> > + */
> > +Request::ErrorFlags Request::error() const
> > +{
> > +     return _d()->error_;
> > +}
> > +
> >  /**
> >   * \brief Check if a request has buffers yet to be completed
> >   *
> > --
> > 2.34.1
> >