[libcamera-devel] [PATCH v5 01/12] libcamera: stream: Add stream hints to StreamConfiguration

[Naushir Patuck]

Hi all,


On Wed, 18 Jan 2023 at 10:09, Kieran Bingham <
kieran.bingham at ideasonboard.com> wrote:

> Hi Naush,
>
> Quoting Naushir Patuck via libcamera-devel (2023-01-18 08:59:42)
> > Add a new hints flags field in the StreamConfiguration structure to
> allow the
> > application to specify certain intended behavior when driving libcamera.
> > Pipeline handlers are expected to look at these hint flags and may
> optimise
> > internal operations based on them.
> >
> > Currently, only one flag is listed, OptionalStream, which the
> application can
> > set to inform the pipeline handler that a buffer may not be provided on
> every
> > Request for a given stream.
>
> Sorry - Laurent had comments on this yesterday when I was discussing
> with him, so I don't know which way it will go yet...
>
> I still think this is the better way around, but we'll have to consider
> that this is an 'ABI' breakage, as now apps that were able to use two
> streams won't unless they explicitly provide all buffers or inform
> libcamera that they won't provide all buffers....
>

Has there been any consensus reached on this?
I'm keen to get out an updated patch by the end of the day if any other
changes are needed.

Regards,
Naush


>
>
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > ---
> >  include/libcamera/stream.h |  8 ++++++++
> >  src/libcamera/stream.cpp   | 24 ++++++++++++++++++++++++
> >  2 files changed, 32 insertions(+)
> >
> > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > index 29235ddf0d8a..233ff0450451 100644
> > --- a/include/libcamera/stream.h
> > +++ b/include/libcamera/stream.h
> > @@ -13,6 +13,8 @@
> >  #include <string>
> >  #include <vector>
> >
> > +#include <libcamera/base/flags.h>
> > +
> >  #include <libcamera/color_space.h>
> >  #include <libcamera/framebuffer.h>
> >  #include <libcamera/geometry.h>
> > @@ -51,6 +53,12 @@ struct StreamConfiguration {
> >
> >         std::optional<ColorSpace> colorSpace;
> >
> > +       enum class Hint {
> > +               None = 0,
> > +               OptionalStream = (1 << 0),
> > +       };
> > +       Flags<Hint> hints;
> > +
> >         Stream *stream() const { return stream_; }
> >         void setStream(Stream *stream) { stream_ = stream; }
> >         const StreamFormats &formats() const { return formats_; }
> > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > index 67f308157fbf..b7de85f8b9c7 100644
> > --- a/src/libcamera/stream.cpp
> > +++ b/src/libcamera/stream.cpp
> > @@ -349,6 +349,30 @@ StreamConfiguration::StreamConfiguration(const
> StreamFormats &formats)
> >   * color spaces can be supported and in what combinations.
> >   */
> >
> > +/**
> > + * \enum StreamConfiguration::Hint
> > + * \brief List of available hint flags provided by the application for
> a stream
> > + *
> > + * \var StreamConfiguration::Hint::None
> > + * No hints for this stream.
> > + * \var StreamConfiguration::Hint::OptionalStream
> > + * Informs the pipeline handler that the application may not always
> provide a
> > + * buffer for the configured stream in every Request. This may ensure
> the
> > + * pipeline handler allocates additional stream buffers for internal
> use.
> > + */
> > +
> > +/**
> > + * \var StreamConfiguration::hints
> > + * \brief Application provided StreamConfiguration::Hint flags for
> specific
> > + * stream behavior
> > + *
> > + * Provides hints from the application to the pipeline handlers on how
> it
> > + * intends on handling a given configured stream. These hints may alter
> the
> > + * behavior of the pipeline handlers, for example, by allocating
> additional
> > + * buffers for internal use if an application does not guarantee
> buffers will be
> > + * provided in every Request for a stream.
> > + */
> > +
> >  /**
> >   * \fn StreamConfiguration::stream()
> >   * \brief Retrieve the stream associated with the configuration
> > --
> > 2.25.1
> >
>
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